Crop yield response to water - Cra

Description of the stages of developmentin relation to yield determinationVegetative and reproductive growthAs with other stone fruit, peach flowering is immediately followed by vegetative growth in earlyspring. Peach chilling requirements, usually computed during dormancy as hours above 7 ºC, varywidely among varieties, but in some may be substantial. During the canopy development period,fruit set and initial fruit growth take place simultaneously. Figure 2a depicts the patterns of fruitgrowth for three cultivars differing in maturity and the relative rate of vegetative growth forthe late-maturing cultivar. Although early maturing cultivars bloom earlier than the late, initialfruit growth is very similar for the three types. In the early cultivar, such initial growth is directlyfollowed by a fast fruit enlargement phase (Figure 2a) that ends with fruit ripening. In the othercultivars, there is a slowdown in growth rate of the fruit, coinciding with the acceleration ofvegetative growth (Figure 2a). Vegetative growth, measured as seasonal shoot length or theincrease in trunk diameter, has similar trends for the different cultivars. Extension of primaryshoots occurs first followed by the growth of secondary shoots. In the early cultivars there aretwo peaks of rapid extension growth, the second one taking place after fruit harvest. In themedium and late-maturing cultivars, there is normally only one peak of fast shoot growth, butthere may be another one after harvest in some cultivars and environments. At some point inthe season, shoot growth slows and the rapid fruit expansion rate period begins (Figure 2b).This last fruit enlargement phase extends until the fruit matures prior to harvest, and the longerthis period, the greater is the accumulation of dry matter in the fruit and the larger is the finalpotential fruit size (Figures 2a and 2b).Because bud emergence usually occurs with a fully charged soil profile, water deficits affectingthe early growth stages of fruit and canopies are uncommon. When they occur, tree leaf areaand final fruit size will be reduced, because in the latter case, initial growth is mostly causedat cell division stage that sets the final number of cells that a fruit will have.Figure 2aEvolution of fruit fresh weight for early (A), medium (B) and late (C) maturing peach cultivars.Stages I, II, and III of fruit growth and postharvest (PH) maturing peach cultivars. Stages I, II,and III of fruit growth and postharvest (PH) for a medium cultivar grown in the NorthernHemisphere are shown.200150S-IIS-IIICFresh fruit weight (g)10050S-IABPH01-Apr.1-May1-June1-July 1-Aug. 31-Aug.1-Oct.Date394crop yield response to water