Abstract
Experiments were performed to monitor (1) uptake and translocation of foliar-applied microdroplets of14C hormones and (2) effects of multiple growth regulator sprays on foliar and fruit growth variables and photosynthate partitioning in Valencia orange trees (Citrus sinensis (L.) Osbeck). The uptake of14C-sucrose,14C-paclobutrazol (PP333), and14C-napthaleneacetic acid (NAA) in 6-month-old greenhouse-grown trees exceeded that of14C-abscisic acid (ABA) and14C-benzyladenine (BA) 48 h after microdroplet application.14C-sucrose transport from the application site was much greater than any other source, especially14C-BA. In a second study, 2-year-old Valencia orange trees were maintained under field conditions and were sprayed to foliar runoff (3 × /week for 3 weeks) with BA, NAA, ABA, PP333, and gibberellic acid (GA3) at 100 μM during flowering and early fruit set. Select branches were then briefly exposed to14CO2 and harvested 24 h later. Both GA3 and BA sprays promoted foliar growth. BA also stimulated fruit growth, whereas GA3 sharply increased fruit dry weight while fruit number decreased. BA and GA3 enhanced14C assimilate export by the foliage to the developing fruit, and GA3 was especially active in promoting fruit sink intensity (14C/dry wt). The other compounds (NAA, ABA, PP333) restricted foliar and fruit growth. They also inhibited transport of14C assimilate from the leaves to the fruit. Results indicate that foliar-applied growth regulators can influence source-sink relations in citrus early in reproductive development by manipulating photoassimilate production and partitioning.
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Mauk, C.S., Bausher, M.G. & Yelenosky, G. Influence of growth regulator treatments on dry matter production, fruit abscission, and14C-assimilate partitioning in citrus. J Plant Growth Regul 5, 111–120 (1986). https://doi.org/10.1007/BF02025962
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DOI: https://doi.org/10.1007/BF02025962