冠层结构对梨叶片光合特性及果实品质的影响

Effect of Canopy Structure on Foliar Photosynthetic Characteristics and Fruit Quality of Pears

冠层结构是影响果树生长发育及丰产优质的重要因素。该研究以20年生‘玉露香’梨大冠分层树形为对照(CK),以冠层整形修剪后的3、4和5个主枝的开心树形为处理(分别记为OCC3b、OCC4b和OCC5b),测定了冠层截获的光合有效辐射、叶片的气体交换、叶绿素荧光和果实品质特性,探讨不同冠层结构内光环境的变化对梨树叶片光合特性及果实品质的影响,探讨果树的光合调控和结实规律,为西北黄土高原产区果树的标准化整形修剪提供理论依据。结果表明:(1)OCC3b、OCC4b和OCC5b的冠层不同方位和不同时刻截获的光合有效辐射(PAR)均高于CK。与CK和OCC5b相比,OCC3b和OCC4b叶片光响应的最大净光合速率(Pnmax)和羧化效率(CE)显著提高。(2)在强光胁迫下,开心树形叶片光呼吸速率(Pr)占总光合速率(Pg)的比例(Pr/Pg)和非光化学淬灭(NPQ)中可恢复组分r(qE)提高,同时不可恢复组分r(qI)降低。(3)OCC3b和OCC4b比OCC5b和CK的单果重、果面红晕面积、果皮花青苷含量、可溶性固形物含量和可溶性总糖含量均显著提高,而可滴定酸含量显著降低。(4)PAR与果面着色面积和果皮花青苷含量呈极显著正相关关系,Pnmax与单果重呈极显著正相关关系,而PAR和Pnmax均与可滴定酸呈极显著负相关关系。研究发现,OCC3b和OCC4b的梨树冠层内可截获更多的光能,叶片光合能力更强,遭遇强光胁迫时能够通过更高效的热耗散和光呼吸进行自我保护,而且开心形树冠结构还能显著提升果实品质。

Canopy structure plays a significant role in growth,development and high-quality and yield of fruit trees.In this study,we compared twenty-year-old pears(Pyrus bretschneideri‘Yuluxiang’)of Open-Central Canopy(OCC)with three boughs(OCC3b),four boughs(OCC4b)as well as five boughs(OCC5b)with those of the large and layered canopy(CK)for the canopy light interception,foliar gas exchange,chlorophyll fluorescence quenching,photorespiration and fruit quality characters,aiming to explore the effects of different light environment within canopy on foliar photosynthesis and fruit quality and elucidate the mechanism of photosynthetic regulation and fruiting regularity and thus provide an important theoretical basis for standardization of fruit trees training and pruning in the Loess Plateau of China.The results demonstrated that:(1)photosynthetically active radiation(PAR)intercepted by OCC3b,OCC4b and OCC5b at different orientations and timing of the day were greater than those by CK significantly.Compared to CK and OCC5b,the leaf maximum net photosynthetic rate(Pnmax)and carboxylation efficiency(CE)of OCC3b and OCC4b were significantly increased.(2)Under high light stress,leaves of OCC can efficiently dissipate excessive light energy by increasing the ratio of photorespiration rate(Pr)to gross photosynthetic rate(Pg)(i.e.Pr/Pg)and reversible component in NPQ[r(qE)]while decreasing irreversible component in NPQ[r(qI)].(3)The single fruit weight(SFW),coloring area at fruit surface(CA),anthocyanidin content in fruit skin(AC),soluble solids content(SS)and total soluble sugar content(TSS)increased significantly while titratable acid content(TA)decreased significantly in OCC3b and OCC4b than those in OCC5b and CK.(4)At the significant level of P<0.01,PAR was positively correlated with CA and AC but negatively correlated with TA,while Pnmax was positively correlated with SFW but negatively correlated with TA.In summarize,OCC3b and OCC4b could increase light energy interception by the canopy,leading to the increased foliar photosynthetic performance and the enhanced photoprotective capacity via more effective thermal dissipation with photorespiration.Accordingly,the improvement of light environment within canopy and leaf photosynthetic capacity after the Open-Central Canopy pruning resulted in the improved fruit quality.