Regulation of photosynthesis through source: sink imbalance in citrus is mediated by carbohydrate content in leaves

摘要: In citrus, the occurrence of a sink effect on photosynthesis (A) is controversial. Leaf carbohydrates and photosynthetic rates in field-grown trees Satsuma mandarin (Citrus unshiu [Mak.] Marc.) cv. Okitsu, were measured to elucidate whether or not demand for photoassimilates regulates A. The data indicated that source-sink imbalances induced by different treatments altered both soluble (sucrose, glucose fructose) insoluble leaves, as well rates. general, girdling defruiting increased starch reduced photosynthesis, whereas source-limiting conditions imposed through partial defoliations had opposite effect. These results are compatible with assumption lack activity leads carbohydrate accumulation feedback inhibition A, vice versa. Further evidence supporting A was provided measurements dry matter:leaf area ratio, since defoliations, example, this ratio vivo sucrose supplementation plants source:sink ratios (control, defoliated, girdled defruited plants) photosynthesis. This suggests sugars may have, per se, potential repress intact active sinks. Based these we propose sugar citrus leaves causes