Night-Warming Priming at the Vegetative Stage Alleviates Damage to the Flag Leaf Caused by Post-anthesis Warming in Winter Wheat (Triticum aestivum L.)

The asymmetric warming in diurnal and seasonal temperature patterns plays an important role in crop distribution and productivity. Asymmetric warming during the early growth periods of winter wheat profoundly affects its vegetative growth and post-anthesis grain productivity. Field experiments were conducted on winter wheat to explore the impact of night warming treatment in winter (Winter warming treatment, WT) or spring (Spring warming treatment, ST) on the senescence of flag leaves and yield of wheat plants later treated with night warming during grain filling (Warming treatment during grain filling, FT). The results showed that FT decreased wheat yield by reducing the number of grains per panicle and per 1,000-grain weight and that the yield of wheat plants treated with FT declined to a greater extent than that of wheat plants treated with WT + FT or ST + FT. The net photosynthetic rate, chlorophyll content, and chlorophyll fluorescence parameters of the flag leaves of wheat plants treated with WT + FT or ST + FT were higher than those under the control treatment from 0 to 7 days after anthesis (DAA) but were lower than those under the control treatment and higher than those of wheat plants treated with FT alone from 14 to 28 DAA. The soluble protein and Rubisco contents in the flag leaves of wheat plants treated with WT + FT or ST + FT were high in the early grain-filling period and then gradually decreased to below those of the control treatment. These contents were greater in wheat plants treated with WT + FT than in wheat plants treated with ST + FT from 0 to 14 DAA, whereas the opposite was true from 21 to 28 DAA. Furthermore, WT + FT and ST + FT inhibited membrane lipid peroxidation by increasing superoxide dismutase and peroxidase activities and lowering phospholipase D (PLD), phosphatidic acid (PA), lipoxygenase (LOX), and free fatty acid levels in the early grain-filling period, but their inhibitory effects on membrane lipid peroxidation gradually weakened during the late grain-filling period. Night-warming priming alleviated the adverse effect of post-anthesis warming on yield by delaying the post-anthesis senescence of flag leaves.

Analyses statistiques des variations des températures et précipitations observées à Niamey et à Nguigmi

Nous avons analysé les variations des cumuls (moyenne) annuels des précipitations et températures (maximales et minimales) observées à Niamey (1961-2014) et à Nguigmi (1960-2015). À partir des anomalies des précipitations et des températures (maximales, moyennes et minimales), nous avons cherché l'existence des tendances et/ou des périodes de stationnarité par l'identification des points de rupture. L'évolution des anomalies des précipitations à la station de Niamey montre une période nettement humide au cours des années 1960, suivie d'une période très sèche dans les années 1970-1980. Cette station est ainsi marquée par deux périodes de stationnarité (1961-1967 et 1968-2014), indiquant des changements majeurs dans les séries des précipitations, avec une tendance décroissante non significative. Ces observations sont quelque peu différentes de celles de la station de Nguigmi, qui n'indique pas de période de rupture avec une tendance croissante non significative. Concernant les températures, les résultats mettent en évidence deux années de rupture déterminant trois périodes de stationnarité pour les températures maximales et moyennes au niveau des deux stations. Aussi, les variations des températures indiquent un taux de réchauffement journalier à Nguigmi qui dépasse le double de celui observé à Niamey, mais le réchauffement nocturne est plus important à Niamey qu'à Nguigmi. Les données de température montrent des tendances croissantes et significatives au niveau des deux stations. We analyzed the variations in cumulative (average) annual precipitations and temperatures (maximum and minimum) observed over Niamey (1961-2014) and Nguigmi (1960-2015). Based on the precipitations and temperatures (maximum, average and minimum) anomalies, the existence of trends and/or periods of stationarity were analyzed to identify breaking points. The variability of precipitations anomalies at the Niamey station shows a clearly wet period during the 1960s followed by a very dry period in the 1970s and 1980s. Thus, this station is marked by two periods of stationarity (1961-1967 and 1968-2014) indicating major changes in the precipitation series with non-significant decreasing trend. These observations are somewhat different from those of the Nguigmi station that shows an increasing trend non-significant with any breaking period. The results regarding temperatures show two years of breaks determining three periods of stationarity for the maximum and average temperatures at the two stations. The temperatures variations indicate also a daily warming rate in Nguigmi which is more than the double of that observed in Niamey but the night warming is more important in Niamey than in Nguigmi. At both stations, the temperatures data show increasing and significant trends.