干旱下小麦旗叶在灌浆期下午保持高光合速率的生理机制

Physiological mechanism of flag leaf on maintaining high photosynthetic rate in the afternoon during the grain filling stage in wheat under drought

为了研究干旱下小麦旗叶在灌浆期下午保持高光合速率的生理机制,2018—2021年度,在防雨棚池栽条件下,以强抗旱性品种‘晋麦47’(‘JM47’)和弱抗旱性品种‘偃展4110’(‘YZ4110’)为材料,采取测墒补灌的方法,设置重度干旱(W1)、中度干旱(W2)、轻度干旱(W3)、适宜供水(W4)4个处理,测定了灌浆前期(EGFS)、中期(MGFS)和中后期(MALGFS)14:00—16:00的旗叶净光合速率(Pn)、相对含水量(RWC)、抗氧化特性、渗透调节物质含量以及成熟期的籽粒产量。结果表明,干旱导致小麦灌浆期下午旗叶Pn和籽粒产量降低且整体上‘JM47’灌浆期下午旗叶Pn和籽粒产量显著高于‘YZ4110’。从3年均值来看,与W4相比,干旱使灌浆期下午的旗叶生理特性整体上表现为RWC和过氧化物酶(POD)、过氧化氢酶(CAT)活性降低,旗叶丙二醛(MDA)、脯氨酸(Pro)和可溶性糖(SS)含量提高,且‘JM47’的变幅多优于‘YZ4110’。与‘YZ4110’相比,干旱下‘JM47’灌浆中期下午的旗叶RWC、POD活性、SS含量,灌浆中后期下午的旗叶RWC、POD活性、CAT活性和Pro含量显著提高,灌浆中期和中后期旗叶下午MDA含量显著降低。相关分析结果表明,除灌浆前期下午‘JM47’旗叶CAT活性、SS含量和‘YZ4110’旗叶CAT活性,以及灌浆中期下午‘JM47’旗叶CAT活性外,灌浆期下午旗叶Pn与旗叶RWC、POD活性、CAT活性显著正相关,与旗叶Pro、SS和MDA含量显著负相关。综上,干旱会降低灌浆期下午旗叶Pn,干旱下强抗旱性品种‘JM47’旗叶在灌浆期下午具有较高的RWC、POD活性、CAT活性、Pro含量、SS含量,较低MDA含量是其维持高Pn的生理基础。

In order to study the mechanism of how the flag leaf maintained high photosynthetic rate in the afternoon during the grain filling stage of wheat under drought,an experiment with two winter wheat cultivars and four water levels was conducted under the condition of rainproof pond cultivation in 2018–2021.The two winter wheat cultivars were'Jinmai47'('JM47',strong drought resistance)and'Yanzhan4110'('YZ4110',weak drought resistance).The four water treatments include severe drought(W1),moderate drought(W2),mild drought(W3),suitable water supply(W4).The net photosynthetic rate(P_n),relative water content(RWC),antioxidant properties and osmotic regulators in flag leaves from 14:00 to 16:00 during the early(EGFS),medium(MGFS),and medium and later(MALGFS)grain filling stage and the grain yield at maturity were investigated.The results showed that drought decreased the P_n in flag leaf in the afternoon during the grain filling stage and grain yield in wheat,and on the whole the P_n and grain yield of'JM47'were significantly higher than that of'YZ4110'.Averaged across the three years,compared with W4,the physiological characteristics of flag leaves in the afternoon during the grain filling stage were as follows:RWC,peroxidase(POD)activities,and catalase(CAT)activities decreased,malondialdehyde(MDA),proline(Pro)content and soluble sugar(SS)content increased,and the amplitude of'JM47'was better than that of'YZ4110'.Compared with'YZ4110',the RWC,POD activity,SS content in flag leaves of'JM47'in the afternoon during MGFS and the RWC,POD activity,CAT activities and Pro content in flag leaves in the afternoon during MALGFS were significantly increased under drought,while the MDA content in flag leaves in the afternoon during MGFS and MALGFS was significantly decreased.The results of correlation analysis showed that,in the afternoon during the grain filling stage,the P_n in flag leaves was positively correlated with RWC,POD activities and CAT activities,but significantly negatively correlated with Pro,SS content and MDA content,except for the CAT activities and SS content for'JM47'and the CAT activities for'YZ4110'during EGFS and the CAT activities in'JM47'during MGFS.In conclusion,drought stress reduced the P_n in flag leaves in the afternoon during the grain filling stage.However,'JM47'with strong drought resistant could maintain the higher RWC,POD activities,CAT activities,and Pro content,SS content,and a lower MDA content in flag leaves in the afternoon,which may be the major physiological basis of'JM47'for maintaining a high flag leaf P_n in the afternoon during the grain filling stage.