![]() ![]() (1995), in a study conducted with potted trees, found that non pollinated fruit were highly susceptible to water stress but fruit drop of well pollinated fruit was low even at moderate leaf water potential (−1.8 MPa). (1988) showed that when the leaf water potentials reached −1.8 MPa, fruit drop of poorly pollinated or non-pollinated fruit increased 5–15 times compared with well-pollinated fruit. (1988) indicated that soil moisture potential should be maintained at −0.0145 MPa during half of the fruit development period to prevent a reduction in fruit development. In persimmon trees, the effect of water stress on fruit drop has been the subject of some research mainly conducted in humid conditions in Japan. Similarly, in pomegranate trees, deficit irrigation applied during the flowering and fruit set period increased tree crop level at harvest, most likely due to a decrease in the drop of the reproductive organs (Intrigliolo et al., 2012). However, in peach trees, water stress might actually decrease the drop of pollinated immature peach fruit before the last phase of fruit growth (Girona et al., 2003). In citrus trees, it has been well documented that some plant water stress during the June fruit drop period might increase fruitlets abscission (Ginestar and Castel, 1996, González-Altozano and Castel, 1999, Romero et al., 2006, García-Tejero et al., 2010). In fact, in general for many woody perennial species, plant water relations can be a determinant factor for tree fruit bearing capacity (Naor, 2006). Increased fruit drop on these soil types may be due to waterlogging, which has been shown to increase fruit drop (Suzuki et al., 1988). Fruit drop is also reported to be heavier on alluvial soils (Kaneko et al., 1979). In addition, several studies conducted in Japan have shown that fruit set is higher in seasons when sunshine duration was higher during and after flowering (Kaneko, 1977, Yamada et al., 1987). (1992) showed that non-pollinated fruit are more susceptible to fruit drop induced by environmental constraints such as low irradiance at anthesis. Previous research investigated the effects of environmental factors on persimmon fruit drop (see review by George et al., 1997). Spring fruit drop is a crucial determinant for persimmon tree production, since the final yield is greatly influenced by the tree crop level (i.e. ![]() ‘Rojo Brillante’ is the most important persimmon cultivar grown and rapidly expanding in the Mediterranean basin because of the fruit's current high commercial value. In semi-arid climates, this knowledge can be used for increasing ‘Rojo Brillante’ persimmon fruit set by restricting irrigation applications during late spring. Early season water stress had a greater effect on reducing fruit abscission during the second wave of fruit drop. However, the timing of water stress also affected the existing relationships. In addition, in the last two experimental seasons, there was a highly significant relationship between the amount of fruit that dropped during the physiological fruit drop and the average Ψ stem for the period of water restrictions. Both DI regimes led to lower fruit drop than the Control (31 and 12% lower fruit drop for DI early and DI late, respectively). The seasonal variation of fruit drop was quantified during the entire fruit abscission period. Plant water stress was monitored by means of midday stem water potential ( Ψ stem) readings. ![]() Three irrigation regimes were tested: Control, always well watered and two deficit irrigation (DI) treatments where water was applied at 50% of the Control regime during May and June (DI early) or during July and August (DI late). To achieve this goal, a field experiment was conducted during three consecutive seasons with mature trees. The main purpose of this study was to establish and quantify the effects of plant water stress on fruit drop of the ‘Rojo Brillante’ persimmon cultivar. In this sense, plant water status might play a pivotal role in persimmon fruit drop occurring during spring. Several environmental and tree endogenous factors can determine the magnitude of this physiological phenomenon. Spring fruit drop is a crucial determinant for yield in persimmon trees. ![]()
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