Leaf senescence and grain filling affected by post-anthesis high temperatures in two different wheat cultivars

Abstract

High temperature is a major factor affecting grain yield and plant senescence in wheat growing regions of central and east China. In this study, two different wheat cultivars, Yangmai 9 with low-grain protein concentration and Xuzhou 26 with high-grain protein concentration, were exposed to different temperature regimes in growth chambers during grain filling. Four day/night temperature regimes of 34°C/ 22°C, 32°C/24°C, 26°C/14°C, and 24°C/16°C were established to obtain two daily temperatures of 28 and 20°C, and two diurnal day/night temperature differences of 12 and 8°C. Concentration of a lipid peroxidation product malondialdehyde (MDA), activities of the antioxidants superoxide dismutase (SOD) and catalase (CAT), chlorophyll concentration (SPAD) in flag leaves and kernel weight were determined. Results show that activities of SOD and CAT in leaves increased markedly on 14 days after anthesis (DAA) for the high-temperature treatment (34°C/22°C) and then declined. As a result, MDA concentration in leaves increased significantly under high temperature (34°C/22°C and 32°C/24°C). Compared with optimum temperature treatment, high temperature reduced the concentration of soluble protein and SPAD values in flag leaves. Grain-filling rate increased slightly initially, but decreased significantly during late grain filling under high temperature. As a result, final grain weight was reduced markedly under high temperature. Decreases in the activities of SOD and CAT and increases in MDA concentration in leaves were more pronounced with a 12°C of day/night temperature difference when under high temperatures. Kernel weight was higher under 12°C of day/night temperature difference under optimum temperatures (24°C/16°C and 26°C/14°C). The responses to high-temperature regimes appeared to differ between the two wheat cultivars with different grain protein concentrations. It is concluded that a larger diurnal temperature difference hastened the senescence of flag leaves under high-temperature conditions, but retarded senescence under optimum temperature treatments of 26°C/14°C and 24°C/16°C.

Natural leaf senescence: probed by chlorophyll fluorescence, CO2 photosynthetic rate and antioxidant enzyme activities during grain filling in different rice cultivars

“…During normal plant growth when the photon intensity is within the range of the utilizing capacity of chloroplasts for CO 2 -fixation, the generation rate of AOS is very low, and these molecules are effectively scavenged. Several researchers observed that during the time of fast growth as well as the plant with greater biomass producing capacity showed greater activities of antioxidant enzyme activities to prevent the excess production of AOS (Gara et al 2000;Hideg et al 2002;Zhao et al 2007). The association of different antioxidant enzymes with Pn and other photosynthetic parameters were showed highly significant positive correlation (Table 1).…”

“…The association of different antioxidant enzymes with Pn and other photosynthetic parameters were showed highly significant positive correlation (Table 1). The significant association was due to the overall decrease of leaf function during natural senescence of flag leaves (Yamazaki and Kamimura 2001;Zhao et al 2007;Falqueto et al 2009). …”

“…The relationship between rate of leaf senescence and grain growth is complex. Grain growth along with leaf senescence is influenced by climatic conditions, varietal types and many other factors (Yamazaki and Kamimura 2001;Huang et al 2004;Zhao et al 2007;Damanik et al 2010;Zhang et al 2010b). Natural leaf senescence is faster in Indica than in Japonica types and in warm regions than in cool regions.…”

Heat tolerance of Portuguese old bread wheat varieties

“…High temperatures may damage plant cell membranes resulting in photosynthesis reductions. Heat stress induces the production of reactive oxygen species, which can bring about peroxidation of membrane lipids, leading to membrane injury (Blum and Ebercon, 1981;Almeselmani et al, 2006;Leshem, 1992), photosynthesis impairment and leaf senescence (Zhao et al, 2007). As observed for other stressful conditions, the ability to maintain membrane integrity and, hence, cell compartmentalization and metabolism, is crucial for plants survival under heat stress.…”

In vivo studies on artificial induction of thermotolerance to detached panicles of wheat (Triticum aestivum L) cultivars under heat stress

“…High temperature during grain filling stage is an important yield limiting factor in wheat (Zhao et al 2007). It has been reported that single grain mass falls by 3-5% for every 1°C rise in temperature above 18°C (McDonald et al 1983).…”