accumulation in the leaves started by early December, and the levels in the leaves were, 34 until bud sprouting, the same in on and off trees. The heavy flower formation which 35 followed an off year caused the rapid mobilization of the stored reserves, which were 36 exhausted at full bloom. We could not find evidence for carbon fixation regulation by 37 fruit demand or by the carbohydrate levels in the leaves. The carbohydrate reserves 38 played no role in fruit set, which relied on current photosynthesis. Koch, 1996). This behaviour is similar to that described in deciduous fruit trees, which 52 accumulate carbohydrate reserves before leaf fall and utilise them during the dormant 53 season and the spring growth (Schaffer et al., 1999), except for some differences in the 54 partitioning of the reserves, and their importance in plant growth regulation and 55 survival. In deciduous trees, the root system is the major storage organ for 56 carbohydrates (Loescher et al., 1990). In Citrus, the root system may still be the major 57 storage organ for carbohydrates, but carbohydrates also accumulate in the leaves at a 58 high concentration (Goldschmidt and Golomb, 1982). The importance of reserve 59 carbohydrates in deciduous trees seems evident. Winter respiration and the beginning of 60 both vegetative and, in some species, reproductive growth, occur in the absence of 61 photosynthesing leaves, and must be totally dependent on reserves (Loescher et al., 62 1990). On the contrary, photosynthesis proceeds in Citrus during winter at a rate high 63 enough to affect growth significantly (Syvertsen et al., 1997; Goldschmidt ,1999).
64Therefore, the reserves should not be as critical for winter and spring growth as in 65 deciduous trees, yet a role for carbohydrate reserves in some aspects of development has 66 been postulated.
67The accumulation of reserves is inversely related to crop load (Goldschmidt and 68 Golomb, 1982), and a depletion of them under heavy crop load has been related to tree 69 collapse (Smith, 1976) and the triggering of an alternate bearing habit (Monselise and 70 Goldschmidt, 1982; Guardiola ,1992; Syvertsen and Lloyd, 1994 carbohydrates (Smith, 1976; Goldschmidt and Golomb, 1982), carbohydrate levels are 73 not the sole factor regulating flower formation (Goldschmidt, 1999; García-Luis and 74 Guardiola, 2000). During flower formation and fruit set, part of the reserves are 75 translocated to the reproductive organs (Akao et al., 1981), but the contribution of the 76 reserves to these processes must vary widely as indicated by the rate of their depletion.
77This rate of depletion may vary among cultivars (Borrás et al., 1984; González-Ferrer et 78 al., 1984), but differences in the rate of depletion within a cultivar have also been 79 reported (García-Luis et al., 1988; Ruiz and Guardiola, 1994; Ruiz et al., 2001). The 80 rate of depletion has been related to flower number (García-Luis et al., 1988).
81There are some studies about the significance of reserves in alternate bearing...
