Gerardo Lopez

Integrating simulation of architectural development and source–sink behaviour of peach trees by incorporating Markov chains and physiological organ function submodels into L-PEACH

L-PEACH is an L-system-based functional-structural model for simulating architectural growth and carbohydrate partitioning among individual organs in peach (Prunus persica (L.) Batsch) trees. The original model provided a prototype for how tree architecture and carbon economy could be integrated, but did not simulate peach tree architecture realistically. Moreover, evaluation of the functional characteristics of the individual organs and the whole tree remained a largely open issue. In the present study, we incorporated Markovian models into L-PEACH to improve the architecture of the simulated trees. The model was also calibrated to grams of carbohydrate, and tools for systematically displaying quantitative outputs and evaluating the behaviour of the model were developed. The use of the Markovian model concept to model tree architecture in L-PEACH reproduced tree behaviour and responses to management practices visually similar to trees in commercial orchards. The new architectural model along with several improvements in the carbohydrate-partitioning algorithms derived from the model evaluation significantly improved the results related to carbon allocation, such as organ growth, carbohydrate assimilation, reserve dynamics and maintenance respiration. The model results are now consistent within the modelled tree structure and are in general agreement with observations of peach trees growing under field conditions.

Spring temperatures have a major effect on early stages of peach fruit growth

Summary Previous research has shown that Spring temperatures within 30 d after bloom (expressed as accumulated growing degree hours, GDH) are useful for predicting the harvest date of specific peach cultivars. The goal of the present research was to explore the relationship between GDH and additional environmental parameters on peach fruit development and growth during the period from the full bloom date (FBD) to the reference date (RD). Since heat accumulation during the first 30 d after bloom is a primary driver of fruit phenology, we hypothesised that years with high early Spring temperatures would result in smaller RD fruit size (RDFS) because trees cannot supply resources rapidly enough to support the potential growth associated with high rates of phenological development. Data on FBD, RD, and RDFS were collected at different locations in California between 1988 – 2004 and were analysed in conjunction with seasonal environmental data including accumulated GDH, rainfall, soil temperature, and solar radiation, from FBD to RD. Early Spring air temperatures appeared to be a primary environmental factor influencing RDFS. GDH accumulation during the first 30 d after bloom (GDH30) caused a decrease in the number of days between FBD and RD. RDFS increased with increases in the number of days between FBD and RD, and was negatively affected during years with high Spring temperatures. High GDH30 accumulations increased the rates of fruit growth d–1 but not enough to compensate for the shorter growth period from FBD to RD that occurred when GDH30 accumulation was high. The data supported the hypothesis that, with excessively high Spring temperatures, trees could not supply resources rapidly enough to support their maximum potential fruit growth rates.

Drought in Deciduous Fruit Trees: Implications for Yield and Fruit Quality

In many production areas of the world deciduous fruit trees require irrigation to maximize yield and optimize fruit quality. Drought could therefore have a negative impact on fruit production. This chapter addresses yield and fruit quality responses of deciduous fruits (DF) to drought. The chapter has emphasis on the most important deciduous fruit trees and includes apple, apricot, cherry, peach, pear, and plum. Confronted with a period of drought, fruit growers’ success will depend on their ability to modify cultural practices. We evaluated various strategies at different levels of water shortage. We expected that this chapter will introduce enough information to understand the effects of drought in deciduous fruit tree orchards and facilitate fruit marketability under water shortage.