Chlorophyll a fluorescence during flag leaf senescence of field‐grown winter wheat plants under drought conditions

Abstract

Improving wheat grain yield plays a significant role in ensuring global food security.Wheat production could be increased by the genetic improvement of wheat genotypes where delayed senescence with enhanced post-anthesis capacity and staygreen traits could have an important role. In this study, chlorophyll a fluorescence (ChlF) rise kinetics from the early until late senescence of flag leaves, grain yield and other agromorphological characteristics were compared for three winter wheat advanced lines under natural drought conditions. The differences between lines were observed when considering the heading date which was 1 and 4 days earlier for the line Osk.4.354/12-18, than lines Osk.4.312/10-18 and Osk.4.330/6-18, respectively. Furthermore, line Osk.4.354/12-18 had the highest test weight (kg hl À1 ), while line Osk.4.330/6-18 showed a tendency of decreased grain yield, compared to the other two lines. Analysis of ChlF transients and several JIP-test parameters indicated that all three lines had a generally similar course of changes in the photosynthetic performance of flag leaves during senescence under drought conditions. However, at the point when a decrease in photosynthetic performance was initiated, it was slightly less intensive in line Osk.4.354/12-18 accompanied by longer preservation of functionality and connectivity of PSII units, than in the other two lines, which contributed to its better agronomical performance. These results indicated that even delicate variations in the functioning of the photosynthetic apparatus of the flag leaf during grain filling were agronomically important, especially when plants were exposed to drought stress, and could be used to differentiate otherwise similar wheat genotypes. Even small genotype-specific differences in the photosynthetic performance of senescing flag leaves, along with earlier heading dates, could assist in the selection of genotypes with a better ability to cope with unfavourable environmental conditions.

Analysis of the Photosynthetic Parameters, Grain Yield, and Quality of Different Winter Wheat Varieties over a Two-Year Period

“…Further, the varieties with the highest grain yield (Bubnjar, Silvija, and Rujana) showed an increase in PI ABS, or a slight decrease in the case of Silvija, from the 6th to the 7th measurement, compared to other varieties showing a pronounced decrease between these two measurements. In the previous research, it was reported that longer integrity of functional PSII units and extended preservation of the optimal level of energetic connectivity among PSII units during grain filling resulted in better agronomic performance [28]. Higher grain yield resulted from increased 1000 kernel weight, which could be related to the source/sink ratio established during the early grain-filling stage [74].…”

“…For example, according to the recent research by Kubar et al [26], fertilization with nitrogen resulted in increased leaf area and significantly prompted the photosynthetic rate, which resulted in an improvement in grain yield. In addition, plants exhibit genetic variations in photosynthetic response under abiotic and biotic stresses [27,28]. When plants are exposed to disease stress factors, especially during the flowering stage, disruption in the photosynthetic apparatus can occur, causing a decrease in plant productivity and overall grain yield [29].…”