During my teaching career that involved a core course designed to prepare graduate students for a career in scientific research, I regularly emphasized that the key to having a career in scientific research is dependent upon developing the skill of asking good, specific questions. Armed with solid, fundamental, general understanding of a specific subject (obtained from the literature and practical experience), followed by focusing on specific questions about the subject, helps in developing ideas for useful research projects, formulating methods for conducting the research and eventually writing up the research. This is easier said than done.
Many students struggle to grasp an understanding of how this is actually works and it is daunting to consider how this is accomplished over the course of an academic career. Many students are also intimidated by the seeming necessity to conduct research using ever-increasing levels of “scientific” technology in sophisticated laboratories. I have conducted a productive, field-based research program over nearly 40 years and have published more than 250 scientific papers with my co-workers. In an effort to demonstrate what such a career in conducting field research can look like I have organized the themes of my research program into eight broad topics with numerous fundamental questions that were asked and answered within each topic. Almost all the answers to the questions posed appear in the form of research papers that have been published and that are available on this website. Most of the research papers also point to additional questions that conducting the research raised and could be used to formulate follow-up research related to the questions asked.
I hope that presenting the results of my career in research in this manner will make the outcomes of my research more meaningful to fruit crop growers and future researchers interested in tree fruit crops. In addition, it is my intent to encourage future researchers interested in developing meaningful research careers in pomology. We have learned a lot, but there is still much research to be done!
Questions addressed by the DeJong Lab and associates related to how fruit trees work.
Topic I. Factors influencing photosynthesis and leaf photosynthetic capacity in fruit trees.
Is leaf nitrogen content a major determinant leaf Pn capacity in leaves of fruit trees?
DeJong, T.M. 1982. Leaf nitrogen content and CO2 assimilation capacity in peach. Journal of the American Society for Horticultural Science 107(6):955‑959.
DeJong, T.M. 1983. CO2 assimilation characteristics of five Prunus tree fruit species. Journal of the American Society for Horticultural Science 108(2):303‑307.
Is individual leaf photosynthetic capacity linked to leaf light exposure and leaf N content within tree canopies?
DeJong, T.M. and J.F. Doyle. 1985. Seasonal relationships between leaf nitrogen content (photosynthetic capacity) and leaf canopy light exposure in peach Prunus persica. Plant, Cell and Environment 8:701‑706.
DeJong, T.M. 1986. Distribution of leaf nitrogen concentration in relation to leaf light exposure in peach tree canopies, In: Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants. p. 319‑321.
Klein, I., T.M. DeJong, S.A. Weinbaum, and T.T. Muraoka. 1991. Specific leaf weight and nitrogen allocation responses to light exposure within walnut trees. HortScience 26(2):183-185.
How does N availability affect the relationship between leaf N content and leaf Pn capacity?
DeJong, T.M., K.R. Day, and R.S. Johnson. 1989. Partitioning of leaf nitrogen with respect to within canopy light exposure and nitrogen availability in peach (Prunus persica). Trees 3:89‑95.
Rosati, A., G. Esparza, T.M. DeJong, and R.W. Pearcy. 1999. Influence of canopy light environment and nitrogen availability on leaf photosynthetic characteristics and photosynthetic nitrogen-use efficiency of field-grown nectarine trees. Tree Physiology 19:173-180.
How does a plant determine how to distribute its N among leaves in different light exposures?
Rosati, A., K.R. Day, and T.M. DeJong. 2000. Distribution of leaf mass per unit area and leaf nitrogen concentration determine partitioning of leaf nitrogen within tree canopies. Tree Physiology 20:271-276.
How does artificial autumn defoliation affect leaf N resorption and subsequent growth in fruit trees?
Castagnoli, S.P., S.A. Weinbaum, and T.M. DeJong. 1989. Nitrogen remobilization and nursery tree growth following autumn defoliation in plum (Prunus salicina) trees. Advances in Horticultural Science 3:115‑119.
Castagnoli, S.P., T.M. DeJong, S.A. Weinbaum, and R.S. Johnson. 1990. Autumn foliage applications of ZnSO4reduced leaf nitrogen remobilization in peach and nectarine. Journal of the American Society for Horticultural Science 115(1):79‑83.
What is the relationship between individual leaf Pn capacity and canopy Pn capacity?
Rosati, A., F.W. Badeck, and T.M. DeJong. 2001. Estimating canopy light interception and absorption using leaf mass per unit leaf area in Solanum melongena. Annals of Botany 88:101-109.
Rosati, A. and T.M. DeJong. 2003. Estimating photosynthetic radiation use efficiency using incident light and photosynthesis of individual leaves. Annals of Botany 91:869-877.
Rosati. A., T.M. DeJong, and G. Esparza. 2002. Physiological basis for light use efficiency models. Acta Horticulturae 584: 89-94.
Is there a relationship between leaf photosynthetic capacity and the productivity of the shoots that bear the leaves?
DeJong, T.M. and K.R. Day. 1991. Relationships between shoot productivity and leaf characteristics in peach canopies. HortScience 26(10):1271-1273.
Klein, I., S.A. Weinbaum, T.M. DeJong and T.T. Muraoka. 1991. Relationship between fruiting, specific leaf weight, and subsequent spur productivity in walnut. Journal of American Society for Horticultural Science 116(3):426-429.
Does reducing shoot growth with the plant growth regulator Paclobutrazol (PP333, Cultar) reduce leaf photosynthesis in peach?
DeJong, T.M. and J.F. Doyle. 1984. Leaf gas exchange and growth responses of mature ‘Fantasia’ nectarine trees to paclobutrazol. Journal of the American Society for Horticultural Science 109(6):878‑882.
Does the presence of fruit affect the leaf photosynthetic rate of vigorously growing peach trees? If so, what is the mechanism involved?
DeJong, T.M. 1986. Fruit effects on photosynthesis in Prunus persica. Physiologia Plantarum 66:149‑153.
DeJong, T.M. 1986. Effects of reproductive and vegetative sink activity on leaf conductance and water potential in Prunus persica L. Batsch. Scientia Horticulturae (29)131‑137.
Topic II. Understanding shoot growth and shoot structure in fruit trees.
What drives daily patterns of shoot growth in peach trees?
Berman, M.E. and T.M. DeJong. 1997. Diurnal patterns of stem extension growth in peach (Prunus persica): Temperature and fluctuations in water status determine growth rate. Physiologia Plantarum 100:361-370.
Do the peak periods of vegetative and reproductive sink activity differ in early and late maturing peach cultivars?
DeJong, T.M., J.F. Doyle, and K.R. Day. 1987. Seasonal patterns of reproductive and vegetative sink activity in early and late maturing peach (Prunus persica) cultivars. Physiology Plantarum 71:83‑88.
How do water stress and crop load affect daily patterns of peach shoot growth?
Berman, M.E. and T.M. DeJong. 1997. Crop load and water stress effects on daily stem growth in peach (Prunus persica). Tree Physiology 17:467-472.
How do water deficits affect shoot growth and shoot structures in almond trees?
Negron, C, L. Contador, B. D. Lampinen, S. G. Metcalf, Y. Guedon, E. Costes and T. M. DeJong. 2014. Differences in proleptic and epicormic shoot structures in relation to water deficit and growth rate in almond trees (Prunus dulcis). Annals of Botany 113:545-554.
How does pruning severity affect shoot structure in young almond trees?
Negron, C, L. Contador, B. D. Lampinen, S. G. Metcalf, Y. Guedon, E. Costes and T. M. DeJong. 2015. How different pruning severities alter shoot structure: A modelling approach in young ‘Nonpareil’ almond trees. Functional Plant Biology 42: 325–335.
How does crop load affect seasonal patterns of shoot growth?
Berman, M.E. and T.M. DeJong. 2003. Seasonal patterns of vegetative growth and competition with reproductive sinks in peach (Prunus persica). Journal of Horticultural Science & Biotechnology 78(3):303-309.
How does crop load and pruning affect subsequent year peach shoot growth?
Gordon, D. and T.M. DeJong. 2007. Current-year and subsequent-year effects of crop load manipulation and epicormic-shoot removal on distribution of long, short and epicormic shoot growth in Prunus persica. Annals of Botany 99:323-332.
How much do previous-year and dormancy conditions affect subsequent shoot growth the following year?
Gordon, D., C. Damiano, and T. M. DeJong. 2006. Preformation in vegetative buds of Prunus persica: factors influencing number of leaf primordial in overwintering buds. Tree Physiology 26:537-544.
Gordon, C., A. Rosati, C. Damiano and T.M. DeJong. 2006. Seasonal effects of light exposure, temperature, trunk growth and plant carbohydrate status on the initiation and growth of epicormic shoots in Prunus persica. J. Hort. Sci. and Biotechnology 81:421-428.
What factors control the rate of the addition of new nodes on peach shoots?
Davidson, A. M., D. Da Silva, S. Saa, P. Mann and T. M. DeJong. 2016. The influence of elevated CO2 on the photosynthesis, carbohydrate status and plastochron of young peach (Prunus persica) trees. Hortic. Environ. Biotechnol. 57(4):364-370.
Davidson A., D. Da Silva and T.M. DeJong. 2017. The phyllochron of well-watered and water deficit mature peach trees varies with shoot type and vigour. AoB PLANTS 9: plx042; doi: 10.1093/aobpla/plx042
Davidson, A., D. Da Silva and T.M. DeJong. 2019. Rate of shoot development (phyllochron) is dependent on carbon availability, shoot type, and rank in peach trees. Trees: Structure and Function https://doi.org/10.1007/s00468-019-01881-y
How do shoot growth and branching patterns vary among almond cultivars?
Negron, C., L. Contador, B. D. Lampinen, S. G. Metcalf, Y. Guedon, E. Costes and T. M. DeJong. 2013. Systematic Analysis of Branching Patterns of Three Almond Cultivars with Different Tree Architectures. J. Amer. Soc. Hort. Sci. 138:407-415.
Are the structures of proleptic and sylleptic shoots similar among peach cultivars?
Prats-Llinàs, M.T., G. López, K. Fyrie, B. Pallas, Y. Guédon, E. Costes and T.M. DeJong. 2019. Long proleptic and sylleptic shoots in peach (Prunus persica L. Batsch) trees have similar, predetermined, maximum numbers of nodes and bud fate patterns. Annals of Botany 123:993-1004.
Can sylleptic shoots borne on epicormic shoots set as much fruit as proleptic shoots in peach trees?
K. Fyhrie, M.T. Prats-Llinàs, G. López and T.M. DeJong. 2018. How does peach fruit set on sylleptic shoots borne on epicormics compare with fruit set on proleptic shoots? Eur. J. Hortic. Sci. 83:3-11.
Why does girdling of peach trees increase fruit size but decrease shoot growth?
Tombesi, S., K. R. Day, R. S. Johnson, R. Phene and T. M. DeJong. 2014. Vigour reduction in girdled peach trees is related to lower midday stem water potentials. Functional Plant Biology, 2014, 41, 1336–1341
Can regulated deficit irrigation (RDI) during Phase II of peach fruit growth be used to reduce shoot growth under California conditions?
Girona, J., M. Mata, D.A. Goldhamer, R.S. Johnson, and T.M. DeJong. 1993. Patterns of soil and tree water status and leaf functioning during regulated deficit irrigation scheduling in peach. Journal of the American Society for Horticultural Science 118(5):580-586.
Topic III. Understanding stress responses of fruit trees.
Is it possible to reduce irrigation after harvest with early maturing peach cultivars to conserve water without reducing yields? What are the negative effects of postharvest water stress in peaches?
Larson, K.D., T.M. DeJong, and R.S. Johnson. 1988. Physiological and growth responses of mature peach trees to postharvest water stress. Journal of the American Society for Horticultural Science 113(3):296‑300.
Johnson, R.S., D.F. Handley, and T.M. DeJong. 1992. Long-term response of early maturing peach trees to postharvest water deficits. J. Amer. Soc. Hort. Sci. 117(6):881-886.
How does salinity stress affect plum tree growth and productivity?
Ziska, Lewis H., Robert B. Hutmacher, Glen J. Hoffman, and Theodore M. DeJong. 1989. Changes in leaf water status associated with salinity in mature, field grown Prunus salicina. Physiologia Plantarum 77:141‑149.
Ziska, Lewis H., Jeffrey R. Seemann, and Theodore M. DeJong. 1990. Salinity induced limitations on photosynthesis in Prunus salicina, a deciduous tree species. Plant Physiology 93:864-870.
Ziska, Lewis H., Theodore M. DeJong, Glen F. Hoffman, and Richard M. Mead. 1991. Sodium and chloride distribution in salt-stressed Prunus salicina, a deciduous tree species. Tree Physiology 8:47-57.
How much does ozone exposure affect almond and plum tree photosynthesis and productivity?
Retzlaff, W.A., T.M. DeJong, and L.E. Williams. 1992. Photosynthesis and growth response of almond to increased atmospheric ozone partial pressures. Journal of Environmental Quality 21:208-216.
Retzlaff, W.A., L.E. Williams, and T.M. DeJong. 1992. Photosynthesis, growth, and yield response of ‘Casselman’ plum to various ozone partial pressures during orchard establishment. Journal of the American Society for Horticultural Science 117(5):703-710.
Crisosto, C.H., W.A. Retzlaff, L.E. Williams, T.M. DeJong, and J.P. Zoffoli. 1993. Postharvest performance evaluation of plum (Prunus salicina Lindel., `Casselman') fruit grown under three ozone concentrations. Journal of the American Society for Horticultural Science 118(4):497-502.
Retzlaff, W.A., W.W. Barnett, L.E. Williams, and T.M. DeJong. 1994. Ozone air pollution increases petroleum spray oil phytotoxicity. HortScience 29(2):93-94.
Topic IV. Understanding the carbon economy of fruit growth.
What is the reason why peach fruit growth follows a double sigmoid growth pattern?
DeJong, T.M. and J. Goudriaan. 1989. Modeling peach fruit growth and carbohydrate requirements: reevaluation of the double‑sigmoid growth pattern. Journal of the American Society for Horticultural Science 114(5):800‑804.
How much photosynthate is required to for fruit growth and respiration? (peach and kiwifruit)
DeJong, T.M. and E.F. Walton. 1989. Carbohydrate requirements of peach fruit growth and respiration. Tree Physiology 5:329‑335.
Walton, E.F. and T.M. DeJong. 1990. Growth and compositional changes in kiwifruit berries from three Californian locations. Annals of Botany 66:285-298.
Walton, E.F., T.M. DeJong, and R.S. Loomis. 1990. Comparison of four methods calculating the seasonal pattern of plant growth efficiency of a kiwifruit berry. Annals of Botany 66:299-307.
Walton, E.F. and T.M. DeJong. 1990. Estimating the bioenergetic cost of a developing kiwifruit berry and its growth and maintenance respiration components. Annals of Botany 66:417-424.
How much does the photosynthesis of peach fruit contribute to the carbon economy of developing peach fruit?
Pavel, E.W. and T.M. DeJong. 1993. Seasonal CO2 exchange patterns of developing peach (Prunus persica) fruits in response to temperature, light and CO2 concentration. Physiologia Plantarum 88:322-330.
What are the relationships between relative growth rate patterns and compositional changes in peach and apple fruit?
Pavel, E.W. and T.M. DeJong. 1993. Relative growth rate and its relationship to compositional changes of nonstructural carbohydrates in the mesocarp of developing peach fruits. Journal of the American Society for Horticultural Science 118(4):503-508.
Pavel, E.W. and T.M. DeJong. 1995. Seasonal patterns of nonstructural carbohydrates of apple (Malus pumilaMill.) fruits: Relationship with relative growth rates and contribution to solute potential. Journal of Horticultural Science 70(1):127-134.
When and how much is peach fruit growth source limited and sink limited?
Pavel, E.W. and T.M. DeJong. 1993. Source- and sink-limited growth periods of developing peach fruits indicated by relative growth rate analysis. Journal of the American Society for Horticultural Science 118(6):820-824.
DeJong, T. M. and Y. L. Grossman. 1995. Quantifying sink and source limitations on dry matter partitioning to fruit growth in peach trees. Physiologia Plantarum 95:437-443.
How do differences in crop load affect peach fruit growth rates and why?
Grossman, Y.L. and T.M. DeJong. 1995. Maximum fruit growth potential and seasonal patterns of resource dynamics during peach growth. Annals of Botany 75:553-560.
Grossman, Y.L. and T.M. DeJong. 1995. Maximum fruit growth potential following resource limitation during peach growth. Annals of Botany 75:561-567.
Can marketable peach crop yields be increased by early thinning?
DeJong, T.M., R.S. Johnson, and S.P. Castagnoli. 1990. Computer simulation of the carbohydrate economy of peach crop growth. Acta Horticulturae 276:97-104.
DeJong, T.M. 2012. Fruit growth and development as it relates to crop load, thinning and climate change. Acta Hort. 962: 233-238
Lopez, G., C. Smith, R. Favreau and T. DeJong. 2008. Using L-PEACH for dynamic simulation of source-sink behavior of peach trees: effects of date of thinning on fruit growth. Acta Hort 803:209-216.
How do spring temperatures influence the timing of fruit maturity?
Marra, F.P., P. Inglese, T.M. DeJong and R.S. Johnson. 2002. Thermal time requirement and harvest time forecast for peach cultivars with different fruit development periods. Acta Horticulturae 592:523-529.
Mimoun, M. Ben and T.M. DeJong. 1999. Using the relation between growing degree hours and harvest date to estimate run-times for peach: A tree growth and yield simulation model. Acta Horticulturae 499:107-114.
Day K., G. Lopez and T. DeJong. 2008. Using growing degree hours accumulated thirty days after bloom to predict peach and nectarine harvest date. Acta Hort. 803:163-166.
DeBuse C., G. Lopez and T. DeJong. 2010. Using spring weather data to predict harvest date for ‘Improved French’ prune. Acta Hort 874:107-112.
Tombesi, S., R. Scalia, J. Connell, B. Lampinen and T. M. DeJong. 2010. Fruit development in almond is influenced by early Spring temperatures in California. J. Hort. Sci. & Biotech. 85: 317–322
How does the relationship between early spring temperatures and fruit maturity dates affect potential fruit size at harvest?
Lopez, G. and T. DeJong. 2008. Using growing degree hours accumulated thirty days after bloom to help growers predict difficult fruit sizing years. Acta Hort. 803:175-180.
Lopez, G., K.R. Day and T.M. DeJong. 2011. Why do early high spring temperatures reduce peach fruit size and yield at harvest? Acta Hort. 903:1055-1062.
Lopez, G. and T.M. DeJong. 2007. High spring temperatures decrease peach fruit size. California Agriculture 61: 31-34.
When is girdling most effective for enhancing fruit size on early maturing nectarines?
Day, K.R. and T.M. DeJong. 1990. Girdling of early season ‘Mayfire’ nectarine trees. Journal of Horticultural Science 65(5):529-534.
How do fruit growth and shoot growth interact in peach trees?
Grossman, Y. L. and T. M. DeJong. 1995. Maximum vegetative growth potential and seasonal patterns of resource dynamics during peach growth. Annals of Botany 76:473-482.
Berman, M.E. and T.M. DeJong. 2003. Seasonal patterns of vegetative growth and competition with reproductive sinks in peach (Prunus persica). Journal of Horticultural Science & Biotechnology 78(3):303-309.
How does crop load and water stress interact to affect fruit growth and quality?
Berman, M.E. and T.M. DeJong. 1996. Water stress and crop load effects on fruit fresh and dry weights in peach (Prunus persica). Tree Physiology 16:859-864.
Mahhou, A., T.M. DeJong, T. Cao, and K.S. Shackel. 2005. Water stress and crop load effects on vegetative and fruit growth of ‘Elegant Lady’ peach [Prunus persica (L.) Batch] trees. Fruits 60:55-68.
Mahhou, A., T.M. DeJong, K.S. Shackel and T. Cao. 2006. Water stress and crop load effects on yield and fruit quality of Elegant Lady peach [Prunus persica (L.) Batsch]. Fruits 61:407-418.
Girona, J., J. Marsal, M. Mata, A. Arbones, and T.M. DeJong. 2004. A comparison of the combined effect of water stress and crop load on fruit growth during different phenological stages in young peach trees. Journal of Horticultural Science and Biotechnology 79:308-315.
How does location in peach tree canopies affect fruit growth rates and final fruit size?
Basile, B., L.I. Solari, and T.M. DeJong. 2007. Intra-canopy variability of fruit growth rate in peach trees grafted on rootstocks with different vigour-control capacity. J. Hort.Sci. and Biotechnology 82:243-256.
How does nitrogen stress affect peach fruit growth and yield?
Saenz, J.L., T.M. DeJong, and S..A. Weinbaum. 1997. Nitrogen stimulated increases in peach yields are associated with extended fruit development period and increased fruit sink capacity. Journal of the American Society for Horticultural Science 122(6):772-777.
Topic V. Developing and evaluating peach training and pruning systems.
How does row orientation affect canopy light conditions in hedgerow peach orchards?
DeJong, T.M. and J.F. Doyle. 1985. The effect of row orientation on light distribution in hedgerow peach tree canopies. Acta Horticulturae 173:159‑166.
How does summer pruning affect canopy light distribution and cropping in peach?
Day, K.R., T.M. DeJong and A.A. Hewitt. 1989. Postharvest and preharvest summer pruning of ‘Firebrite’ nectarine trees. HortScience 24(2):238‑240.
How do the yields of four different training systems for peach nectarine and plum compare over time?
DeJong, T.M., K.R. Day, and J.F. Doyle. 1992. Evaluation of training/pruning systems for peach, plum and nectarine trees in California. Acta Horticulturae 322:99-105.
Description of the KAC-V for peach production.
DeJong, T. M., K. R. Day, J. F. Doyle, and R.S. Johnson. 1994. The Kearney Agricultural Center Perpendicular "V" (KAC-V) orchard system for peaches and nectarine. HortTechnology 4(4):362-367.
What is the economic yield efficiency of the KAC-V system compared to two other California peach training systems?
DeJong, T.M., W. Tsuji, J.F. Doyle, and Y.L. Grossman. 1999. Comparative economic efficiency of four peach product systems in California. HortScience 34(1):73-78.
Why does the KAC-V system out-perform the open vase and cordon peach training systems?
Grossman, Y.L. and T.M. DeJong. 1998. Training and pruning system effects on vegetative growth potential, light interception, and cropping efficiency in peach trees. Journal of the American Society of Horticultural Science 123(6):1058-1064.
Topic VI. The search for new size-controlling peach rootstocks and understanding how they work.
New size-controlling peach rootstocks.
DeJong, T.M., D. Ramming, R.S. Johnson, and J. Doyle, 2004, Peach and nectarine rootstock named ‘K146-43’. United States Plant Patent No. US PP15,228 P2
DeJong, T.M., D. Ramming, R.S. Johnson, and J. Doyle, 2004, Peach and nectarine rootstock named ‘P30-135’. United States Plant Patent No. US PP15,225 P2
Bliss, F.A., A.A. Almehdi., T.M. DeJong, A. Gillen, C.A. Ledbetter. 2012. Peach tree rootstock named `HBOK 50` United States Patent PP22.208
Bliss, F.A., A.A. Almehdi., T.M. DeJong, A. Gillen, C.A. Ledbetter. 2012. Peach tree rootstock named `HBOK 10` United States Patent PP22.505
Bliss, F.A., A.A. Almehdi., T.M. DeJong, A. Gillen, C.A. Ledbetter. 2012. Peach tree rootstock named `HBOK 32` United States Patent PP22,845
Bliss, F.A., A.A. Almehdi., T.M. DeJong and C.A. Ledbetter. 2013. Peach tree rootstock named `HBOK 27` United States Patent PP 23,631
How do size-controlling peach rootstocks affect shoot growth characteristics of peach trees?
Weibel, A., R.S. Johnson, and T.M. DeJong. 2003. Comparative vegetative growth responses of two peach cultivars grown on size-controlling versus standard rootstocks. J. Amer Soc. Hort. Sci. 128(4):463-471.
How do seasonal patterns of root growth differ among several size-controlling peach rootstocks?
Basile, B., D.R. Bryla, M.L.Salsman, J. Marsal, C. Cirillo, R.S. Johnson, and T.M. DeJong. 2007. Growth patterns and morphology of fine roots of size-controlling and invigorating peach rootstocks. Tree Physiology 27: 231-241.
Are the differences in shoot growth rates among tree on size-controlling rootstocks related to differences in daily dynamics of stem water potential?
Basile, B., J. Marsal, and T.M. DeJong. 2003. Daily shoot extension growth of peach trees growing on rootstocks that reduce scion growth is related to daily dynamics of stem water potential. Tree Physiology 23:695-704.
Solari, L.I., S. Johnson, and T.M. DeJong. 2006. Relationship of water status to vegetative growth and leaf gas exchange of peach (Prunus persica) trees on different rootstocks. Tree Physiology 26:1333-1341.
Are differences in shoot growth on size-controlling rootstocks related to differences in hydraulic conductance of rootstocks?
Basile, B., J. Marsal, L.I. Solari, M.T. Tyree, D.R. Bryla, and T.M. DeJong. 2003. Hydraulic conductance of peach trees grafted on rootstocks with differing size-controlling potentials. Journal of horticultural Science & Biotechnology 78(5):768-774.
Solari, L.I., S. Johnson, and T.M. DeJong. 2006. Hydraulic conductance characteristics of peach (Prunus persica) trees on different rootstocks are related to biomass production and distribution. Tree Physiology 26: 1343-1350.
Solari, L.I., F. Pernice, and T.M. DeJong. 2006. The relationship of hydraulic conductance to root system characteristics of peach (Prunus persica) rootstocks. Physiologia Plantarum 128:324-333.
Solari, L.I. and T.M. DeJong. 2006. The effect of root pressurization on water relations, shoot growth, and leaf gas exchanges of peach (Prunus persica) trees on rootstocks with differing growth potential and hydraulic conductance. J. Experimental Botany 57: 1981-1989.
Are differences in hydraulic conductance among size-controlling vs. standard peach rootstocks related to differences in xylem characteristics of those rootstocks?
Tombesi, S., R.S. Johnson, K.R. Day and T.M. DeJong. 2010. Relationships between xylem vessel characteristics, calculated axial hydraulic conductance and size-controlling capacity of peach rootstocks. Annals of Botany 105:327-331.
Are the differences in xylem characteristics of size-controlling peach rootstocks limited to the roots or do these rootstocks also influence the xylem structure of scions?
Tombesi S., R.S. Johnson, K.R. Day and T.M DeJong. 2010. Interactions between rootstock, inter-stem and scion xylem vessel characteristics of peach trees growing on rootstocks with contrasting size-controlling characteristics. AoB PLANTS 2010: plq013,
Can differences in rootstock xylem characteristics be used to phenotype size-controlling rootstocks?
Tombesi, S., A.Almehdi, and T.M. DeJong. 2010. Phenotyping vigour control capacity of new peach rootstocks by xylem vessel analysis. Scientia Horticulturae 127: 353–357
Bruckner, C. H. and T. M. DeJong. 2014. Proposed pre-selection method for identification of dwarfing peach rootstocks based on rapid shoot xylem vessel analysis. Scientia Horticulturae 165:404-409.
Do we have an integrated understanding of how size-controlling rootstocks work?
Basile, B. and T.M. DeJong. 2019. Control of Fruit Tree Vigor Induced by Dwarfing Rootstocks. Horticultural Reviews 46:39-98.
Are differences in the size-controlling potential of selected rootstocks related to hormone interactions between scions and rootstocks?
Pernice, F., L. Solari, and T.M. DeJong. 2006. Comparison of growth potentials of epicormic shoots of nectarine trees grown on size-controlling and vigorous rootstocks. J. Hort. Sci. and Biotechnology 81:211-218.
DeJong, T.M., S. Tombesi, B. Basile and D. Da Silva. 2013. Beakbane and Thompson (1939, East Malling) had it right: scion vigour is physiologically linked to the xylem anatomy of the rootstock. Aspects of Applied Biology 119:51-58
DeJong, T.M. and Basile, B. 2022. How do dwarfing rootstocks control fruit tree vigor? (Is it about hormones, nutrients, carbohydrates or water?). Acta Hortic. 1346, 571-584
DOI: 10.17660/ActaHortic.2022.1346.72
Topic VII. Developing an understanding of tree shoot growth and spur dynamics in determining the productivity of nut trees.
How are individual spur light exposure, spur leaf N content and spur fruit bearing related in mature bearing walnut trees?
Klein, I., T.M. DeJong, S.A. Weinbaum, and T.T. Muraoka. 1991. Specific leaf weight and nitrogen allocation responses to light exposure within walnut trees. HortScience 26(2):183-185.
Klein, I., S.A. Weinbaum, T.M. DeJong and T.T. Muraoka. 1991. Relationship between fruiting, specific leaf weight, and subsequent spur productivity in walnut. Journal of American Society for Horticultural Science 116(3):426-429.
Klein, I., S.A. Weinbaum, T.M. DeJong, and T.T. Muraoka. 1991. Spur light exposure as a primary external cause for derivation of DRIS norms in walnut trees. Journal of Plant Nutrition 14(5):463-484.
Deng, X., S.A. Weinbaum, T.M. DeJong, and T.T. Muraoka. 1991. Pistillate flower abortion in ‘Serr’ walnut associated with reduced carbohydrate and nitrogen concentrations in wood and xylem sap. Journal of the American Society for Horticultural Science 116(2):291-196.
What influences the growth and structure of pistachio shoots and how is that related to cropping?
Spann, T.M., R.H. Beede, and T.M. DeJong. 2007. Preformation in vegetative buds of Pistachio (Pistacia vera): relationship to shoot morphology, crown structure and rootstock vigor. Tree Physiology 27: 1189-1196.
Spann, T.M., R.H. Beede, and T.M. DeJong. 2008. Neoformed growth responses to dormant pruning in mature and immature pistachio trees grown on different rootstocks. Journal of Horticultural Science & Biotechnology 83:137-142.
Spann, T.M., R.H. Beede, and T.M. DeJong. 2008. Seasonal carbohydrate storage and mobilization in bearing and non-bearing pistachio (Pistacia vera) trees. Tree Physiology 28:207-213.
Spann, T.M., R.H. Beede, and T.M. DeJong. 2009. Contributions of short- and long-shoots to yield of ‘Kerman’ pistachio (Pistacia vera L.) Scientia Horticulturae 121:495–500
How does water stress during the harvest period affect leaf function and persistence in almond trees?
Klein, I., G. Esparza, S.A. Weinbaum, and T.M. DeJong. 2001. Effects of irrigation deprivation during the harvest period on leaf persistence and function in mature almond trees. Tree Physiology 21:1063-1072.
How do the negative effects of water stress during harvest affect tree carbohydrate and nitrogen status during subsequent dormant seasons?
Esparza, G., T.M. DeJong, and S.A. Weinbaum. 2001. Effects of irrigation deprivation during the harvest period on nonstructural carbohydrate and nitrogen contents of dormant, mature almond trees. Tree Physiology 21:1081-1086.
How do the negative affects of water stress during harvest on leaf function and tree carbohydrate status affect yield determinants of almond trees over time?
Esparza, G., T.M. DeJong, S.A. Weinbaum, and I. Klein. 2001. Effects of irrigation deprivation during the harvest period on yield determinants in mature almond trees. Tree Physiology 21:1073-1079.
What are the relationships among spur leaf characteristics, spur fruit bearing, spur return bloom and sur survival in almond trees?
Heerema, R.J., S.A. Weinbaum, F. Pernice, and T.M.DeJong. 2008. Spur survival and return bloom in almond [Prunus dulcis (Mill.) D.A. Webb] varied with spur fruit load, specific leaf weight, and leaf area. Journal of Horticultural Science and Biotechnology 83:274-281.
Is nitrogen stress more apparent in shaded, fruiting spurs than more exposed non-fruiting spurs?
Heerema, R.J., S.A. Weinbaum, B.D. Lampinen, and T.M. DeJong. 2009. Is nitrogen stress more apparent in shaded, fruiting spurs than exposed, non-fruiting spurs? Journal of Horticultural Science & Biotechnology 84:355-359.
Is previous year spur leaf area related to spur fruit bearing and spur mortality?
Lampinen, B.D., S. Tombesi, S.G. Metcalf, and T.M. DeJong, 2011. Spur behaviour in almond trees: relationships between previous year leaf area, fruit bearing and mortality. Tree Physiology 31:700-706
What is the relationship between individual spur and orchard level fruit bearing in almond?
Tombesi, S., B.D. Lampinen, S.Metcalf and T.M. DeJong. 2011. Relationships between spur- and orchard-level fruit bearing in almond (Prunus dulcis). Tree Physiology 31: 1413–1421
How does spur fruit set affect current year spur leaf area in almond trees?
Tombesi, S., B.D. Lampinen, S. Metcalf and T.M. DeJong. 2015. Spur fruit set is negatively related with current-year spur leaf area in almond. Hortscience 50(2):322–325.
What is a more important determinant of almond tree yields, the abundance of flowers or the percent of flowers that set fruit?
Tombesi, S., B. D. Lampinen, S. Metcalf and T. M. DeJong. 2016. Yield in almond is related more to the abundance of flowers than the relative number of flowers that set fruit. California Agriculture 71: 68-74.
Can nitrogen application be effective for increasing spur survival and return bloom in almonds?
Saa, S., E. Ferna´ndez, S. Muhammad, A. Olivos-Del Rı´o, T. M. DeJong, E. Laca and P. Brown. 2017. Increases in leaf nitrogen concentration and leaf area did not enhance spur survival and return bloom in almonds (Prunus dulcis [Mill.] DA Webb). Acta Physiol. Plant. 39:107
An integrated understanding of how spur dynamics influences cropping in almond trees.
Lampinen, B., Tombesi, S., Metcalf, S.G. and DeJong, T.M. 2018. Spur dynamics: the key to understanding cropping in almond trees. Acta Hort. 1219, 185-192.
Topic VIII. Developing an integrated understanding of the carbohydrate dynamics, growth, structure and productivity of fruit trees – fruit tree simulation modelling.
(The groundwork for developing fruit tree models consisted on many of the above-mentioned studies.)
How to begin thinking about how to model fruit trees?
DeJong, T.M. and J. Goudriaan. 1989. Modeling the carbohydrate economy of peach fruit growth and crop production. Acta Horticulturae 254:103-108.
DeJong, T.M. and Y.L. Grossman. 1992. Modelling the seasonal carbon economy of deciduous tree crops. Acta Horticulturae 313:21-28.
DeJong, T. M. and Y. L. Grossman. 1994. A supply and demand approach to modeling annual reproductive and vegetative growth of deciduous fruit trees. HortScience 29(12):1435-1442.
How well could tree biomass and fruit growth be estimated over time with the information we started with?
Grossman, Y. L. and T. M. DeJong. 1994. PEACH: A simulation model of reproductive and vegetative growth in peach trees. Tree Physiology 14: 329-345.
DeJong, T.M., Y.L. Grossman, S.F. Vosburg, and L.S. Pace. 1996. PEACH: A user friendly peach tree growth and yield simulation model for research and education. Acta Horticulturae 416:199-206.
Esparza, G., C. Gallegos, A. Rumayor, and T.M. DeJong. 2002. Modeling productivity of Zacatecan peaches. Acta H orticulturae 584:21-28.
Can the PEACH model be used to understand how time of fruit maturity influences yield potential in peach trees?
Berman, M.E., A. Rosati, L. Pace, Y.L. Grossman, and T.M. DeJong. 1998. Using simulation modeling to estimate the relationship between date of fruit maturity and yield potential in peach. Fruit Varieties Journal 52(4):229-235.
DeJong, T.M., R.S. Johnson, and S.P. Castagnoli. 1990. Computer simulation of the carbohydrate economy of peach crop growth. Acta Horticulturae 276:97-104.
Could the PEACH model be expanded to simulate seasonal nitrogen dynamics if peach trees?
Rufat, J. and T. M. DeJong. 1999. Modeled seasonal pattern of nitrogen requirements of mature, cropping peach trees (Prunus persica (L.) Batsch). Acta Horticulturae 499:129-135.
Can the PEACH model be adapted to simulate almond and plum tree production?
Esparza, G., T.M. DeJong, and Y.L. Grossman. 1998. Modeling the vegetative and reproductive growth of almonds. Acta Horticulturae 470:324-331.
Esparza, G., T.M. DeJong, and Y.L. Grossman. 1999. Modifying ‘peach’ to model the vegetative and reproductive growth of almonds. Acta Horticulturae 499:91-98.
Mariscal, M.J., K.R. Day, B.Basile, and T.M. DeJong. 2002. Modeling the vegetative and reproductive growth of plums. Acta Horticulturae 584: 35-42.
Can the PEACH model be converted into a virtual tree simulation model to simulate context specific carbohydrate distribution within peach trees using L-systems?
Allen, M.T., T.M. DeJong, and P. Prusinkiewicz. 2002. Using L-systems to model carbon transport and partitioning in developing peach trees. Acta Horticulturae 584:29-34.
Allen, M.T., P. Prusinkiewicz, and T.M. DeJong. 2005. Using L-systems for modeling source-sink interactions, architecture and physiology of growing trees: the L-PEACH model. New Phytologist 166:869-888.
Allen, M., T. DeJong, and P. Prusinkiewicz. 2006. L-PEACH, an L-Systems based model for simulating the architecture and carbon partitioning of growing fruit trees. Acta Hort. 707:71-76.
Allen, M.T., P. Prusinkiewicz, R.R. Favreau, and T.M. DeJong. 2007. L-PEACH, an L-system-based model for simulating architecture, carbohydrate source-sink interactions and physiological responses of growing trees. In: Functional-Structural Plant Modelling in Crop Production, J. Vos, L. Marcelis, P. de Visser and P. Struik eds. Frontis, Wageningen, Netherlands. p 139-150.
Prusinkiewicz, P., M. Allen, A. Escobar-Gutierrez and T.M. DeJong. 2007. Numerical methods for transport-resistance sink-source allocation models. In: Functional-Structural Plant Modelling in Crop Production, J. Vos, L. Marcelis, P. de Visser and P. Struik eds. Frontis, Wageningen, Netherlands. p 123-138.
DeJong, T.M., R. Favreau, M. Allen and P. Prusinkiewicz 2008. Using computer technology to study, understand and teach how trees grow. Acta Hort 772 : 143-150.
Can the structural accuracy of simulated peach trees be improved using hidden Markov-chain sub-models of shoot architectures?
Lopez, G., R. R. Favreau, C. Smith, E. Costes, P. Prusinkiewicz and T. M. DeJong. 2008. Integrating simulation of architectural development and source–sink behaviour of peach trees by incorporating Markov chains and physiological organ function submodels into L-PEACH. Functional Plant Biology 35:761-771.
Smith, C., E. Costes, R. Favreau, G. Lopez and T. DeJong. 2008. Improving the architecture of simulated trees in L-PEACH by integrating Markov chains and responses to pruning. Acta Hort. 803: 201-208.
Can L-Peach be used to simulate the effects of fruit thinning on peach fruit size and yield?
Lopez, G., C. Smith, R. Favreau and T. DeJong. 2008. Using L-PEACH for dynamic simulation of source-sink behavior of peach trees: effects of date of thinning on fruit growth. Acta Hort 803:209-216.
Can the L-Peach modeling approach used to simulate carbon distribution in trees also be used to model water uptake and distribution as well as estimate organ water potentials?
Da Silva, D, R. Favreau, I. Auzmendi, T. DeJong. 2011. Linking water stress effects on carbon partitioning by introducing a xylem circuit into L-PEACH. Annals of Botany 108:1135-1145.
How can seasonal patterns of tree carbohydrate storage and remobilization be incorporated into the L-Peach model?
Da Silva, D., L. Qin, C. DeBuse and T. M. DeJong, 2014. Measuring and modelling seasonal patterns of carbohydrate storage and mobilization in the trunks and root crowns of peach trees. Annals of Botany 114:643-652.
DeJong, T.M. 2017. The understanding of carbohydrate budgets in fruit trees made easy: what we know and ideas about what we need to know. Acta Hort. 1177:29-39.
What are the take-home lessons from thirty years of fruit tree modeling?
DeJong, T.M. 2019. Opportunities and challenges in fruit tree and orchard modelling. Eur. J. Hortic. Sci. 84:117-123.
Grisafi, F., T. M. DeJong. and S. Tombesi. 2021. Fruit tree crop models: an update. Tree Physiology 00, 1–17 https://doi.org/10.1093/treephys/tpab126
DeJong, T. M. 2022. Simulating fruit tree growth, structure and physiology using L-Systems. Crop Science/Horticultural Reviews 62: 2091-2106 https://doi.org/10.1002/csc2.20847