Abstract:

【Objective】 In view of the contradiction between the optimum temperature required for the growth and development of winter wheat and the actual temperature provided in the environment in the north of North China Plain, we attempted to artificially increase the temperature from the end of January to the end of March through plastic-film greenhouse and study the effect of temperature on photosynthesis and flag leaf senescence of winter wheat, in order to provide theoretical and methodological basis for delaying wheat senescence by regulating temperature and tapping the yield potential of winter wheat in North China Plain.【Method】 Field experiments were conducted at Shenzhou Dry-Farming and Water-Saving Agricultural Test Station of Hebei Academy of Agricultural and Forestry Sciences in two consecutive growing seasons from 2015 to 2017. Using ‘Hengguan 35’ as experimental material, greenhouses were constructed in late winter and early spring. Four treatments were set up, i.e., cover 2 layers of plastic film (M2E, January 25-March 25), 2 layers of plastic film (M2L, February 5-March 25), 1 layer of plastic film (M1, February 20-March 25), and conventional production control (CK). Temperature and wheat production and development time were regulated by covering porous and non-porous plastic film and its covering time, which resulted in different growth and development processes in the same date, and the same growth process in different dates and temperatures. During the experiment, the beginning time of each growth period was recorded, and the indexes of photosynthetic characteristics, senescence-related enzymes activity, yield, and water use efficiency were measured. 【Result】 The treated wheat was in a relatively higher temperature in pre-jointing stage and lower temperature after jointing, it promoted the wheat to grow earlier and prolong its developing period. The winter wheat in M2E treatment was 7-8 days earlier than the control in flowering and 3-4 days earlier in ripening; At grain filling stage, the net photosynthetic rate of flag leaf increased by 24.9%, the relative content of chlorophyll, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) increased by 13.3%, 17%, 17% and 14.2%, respectively, while the content of malondialdehyde (MDA) decreased by 22.7%. Flag leaf area increased by 27% at flowering, grain yield increased by 22.8% at harvest and water use efficiency increased by 15.2%. With the delay of warming time and the shortening of covering time, the difference of the above indexes was smaller and smaller, so that there was no significant difference between M1 treatment and CK treatment. 【Conclusion】 Warming in late-winter and early-spring not only significantly prolonged the filling time of wheat, but also maintained higher photosynthesis of flag leaves and delayed senescence of flag leaves, which provided more material basis for grain filling, and promoted the efficient use of water at the same time of obtaining high yield. Increasing temperature in late winter and early spring could be suitable for rational allocation of heat resources and growth and development needs of winter wheat in the north of North China Plain. At the same time, it could not only alleviate the harm of late spring cold on wheat, but also avoid the influence of dry-hot wind on wheat in later growth stage.

Key words: winter wheat, artificial warming, photosynthetic characteristics, flag leaf senescence, grain yield