果实不同发育阶段去果对桃源叶光合作用的影响

Leaf Photosynthesis in Response to Fruit Thining at Different Phenological Stages of Fruit Development in Peach Trees

以大久保桃为试材,在果实发育的不同阶段通过去果处理降低库力,同时设留果对照,并通过环剥和保留相同数量叶片严格控制库源关系,进行了源叶净光合速率(Pn)、碳水化合物含量及其淀粉代谢相关酶活性变化及 Pn 与气孔导度(Gs)、叶表面温度(TLeaf)等相互关系的研究。结果表明,与留果对照相比,去果处理源叶 Pn、 Gs 和蒸腾速率(E)显著降低,但在中午前后一段时间内 TLeaf显著升高;除在果实迅速生长期间的叶片中淀粉含量外,去果对源叶细胞间 CO2浓度、可溶性糖含量、还原糖含量、腺苷二磷酸葡萄糖焦磷酸化酶和淀粉酶活性无影响;源叶 Pn 与 Gs 呈极显著抛物线正相关、与 E 呈极显著直线正相关。无论是留果对照还是去果处理,源叶 Pn 在一定的温度范围内较高,当 TLeaf超过其适宜的临界温度 (38℃)后,Pn 急剧降低,且在相同 TLeaf的情况下,尤其是当 TLeaf高于 38℃时,去果处理源叶 Pn 均显著低于留果对照。因此,在果树库力降低时,气孔开张度减小、TLeaf升高,可能是其 Pn 调控的重要机制之一。

Fruit thining (DF) and retaining fruit (CK) were carried out at different phenological stages of fruit development on one-year-old shoot of Okubo peach trees [Prunus persica (L.) Batsch.] through preventing exportation of the assimilates to the non experimental parts of the tree by girdling one-year-old shoot and keeping the same leaves between fruit thining and CK. The results showed that fruit thining significantly decreased net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (E), but significantly increased leaf surface temperature (TLeaf) at midday as compared with CK. Internal CO2 concentration, soluble sugar content, reductive sugar content, starch content except that at the final fruit rapid growth stage, ADP-glucose pyrophosphorylase and amylase activity in source leaves were not significantly affected by fruit thining. There was a significant positive parabolic correlation between Pn and Gs, and a strong positive linear correlation between Pn and E. Moreover, Pn increased with the increase of TLeaf if TLeaf was lower than 38℃, then decreased sharply when TLeaf exceeded this critical temperature for both fruit thining and CK. Pn of fruit thining was lower than that of CK in the same TLeaf, especially if TLeaf was higher than 38℃. It is suggested that the decreased stomatal aperture and increased leaf temperature may be an important mechanism in regulating photosynthesis under a decreased strength of sink demand by fruit thining in fruit trees.