Carbohydrate and mineral nutrition of orange fruitlets in relation to growth and abscission

Abstract

Carbohydrate and mineral nutrition was studied in relation to abscission in fruitlets from leafy inflorescences of the Washington navel orange (Citrus sinensis [L.] Osbeck). Differences in the growth rate of the fruitlets permitted to predict abscission several weeks in advance. This allowed characterization of early differences in composition and behaviour of persisting and abscising fruitlets. Inflorescences with persisting fruitlets accumulated more mineral elements than inflorescences with abscising fruitlets, and for the phloem‐mobile elements the excess accumulation was allocated to the fruitlets. Starch accumulated in the inflorescence leaves during early fruitlet growth, and this accumulation was enhanced by the persisting fruitlets despite their higher growth rate and mobilizing ability. The relations between the fruitlets and the inflorescence leaves cannot be explained totally in terms of source sink relationships; a hormonal regulation of the leaves by the fruitlets is postulated. Acid invertase activities and hexose concentration in the pericarp were higher in the abscising fruitlets. The lower early growth rate of these fruitlets is thus not caused by a limitation in carbohydrate supply. It seems more related to carbohydrate utilization, probably hormonally mediated, as demonstrated by the higher dependence on hormone supply for the growth in vitro of the endocarp explants.

De novo assembly and characterization of fruit transcriptome in Litchi chinensis Sonn and analysis of differentially regulated genes in fruit in response to shading

“…According to these two criteria, 11 of the selected differentially regulated shading-responsive genes are regarded as being involved in the process of fruitlet abscission. Six of these genes are also documented as being related to the shedding of plant organs,including CHI [26,27,61], FFU [62], GH3 [63], SAMDC [64], MYB [28] and PMEI [65]. The remaining five genes ( AS , ACL , TNL1 , UBCE2 and LL-DAP-AT ) have not yet been reported in the literature to be involved in organ shedding.…”

Diagnosis and Remediation of Nutrient Constraints in Citrus

“…The timing of such foliar sprays may be very important, but the response may not be directly nutritional (Albrigo 1999). Trees may not be able to translocate sufficient major nutrients (NPK) to large numbers of flowers following the initiation of flower bud differentiation due to depletion of nutrients of older leaves during the flowering and fruit set periods along with a large accumulation of nutrients in new leaves and setting fruits (Sanz et al 1987;Ruiz and Guardiola 1994). A large variation exists with regard to foliar recommendation of micronutrients containing inorganic salts as well as synthetic chelates (Table 5.5).…”

Long‐term impact of deficit irrigation on the physical quality of berries in ‘Crimson Seedless’ table grapes

“…11 Moreover, softening has also been associated with the flow of carbohydrates and osmotically active nutrients to the fruit due to competition for the accumulated reserves between vegetative and reproductive growth and the differences in the movement of solutes as a result of phyto-hormonal action. 12 The need to optimise available water resources in Mediterranean areas has led to development of new water saving techniques, which have increased crop water use efficiency. Among such strategies is regulated deficit irrigation (RDI), as defined by Chalmers et al, 13 which is based on reducing irrigation during certain periods of the growth cycle when the crops have a low sensitivity to water stress, from veraison in the case of table grapes.…”