Abstract: Agrometeorological disaster is one of the main factors restricting high yield and quality of crops. The waterlogging and low illumination caused by continuous overcast and rainy weather in the middle and lower reaches of the Yangtze River seriously influence the growth and development of wheat. To explore the effects of continuous overcast and rainy weather on the growth and development of wheat, a controlled experiment with three stress types (waterlogging, low illumination, waterlogging + low illumination) and three durations (5, 10 and 15 d) during elongation and booting stages of winter wheat was conducted in Jiangsu Academy of Agricultural Sciences, with cultivars Ningmai 13 and Yangmai 23 as experimental materials. We measured plant height, tiller number, chlorophyll content and photosynthetic rate of wheat leaf blades during stress process and postdisaster recovery tests. The results showed that different stress types delayed the development of both cultivars, with greatest synergistic effects of waterlogging and low illumination at the jointing stage. For all different stress types at booting stage, the delay of filling and maturity process became more obvious with the extension of treatment time. Plant height was affected by the stress at jointing stage and booting stage. Waterlogging and waterlogging + low illumination treatments significantly affected plant height, while low illumination alone had a weak effect. A stronger effect on plant height was found at booting stage stress than at jointing stage. Under waterlogging and waterlogging + low illumination stress in different growth stages, the chlorophyll content of wheat decreased in varying degrees, but the response to low illumination was variable. When low illumination alone was applied for five days at jointing stage, the chlorophyll content was higher than that of the control, but decreased to the lower level of the control with the increased stress duration. The chlorophyll content of wheat under low illumination stress at booting stage was higher than that of the control. The effects of different stresses on the photosynthetic rate of wheat were as follows: the longer the jointing and booting stage was stressed by waterlogging or low illumination, the greater the decline of photosynthetic rate. The photosynthetic rate at jointing stage was the most sensitive to the synergistic effect of waterlogging and low illumination, and the change of the photosynthetic rate at booting stage was the most obvious under single waterlogging treatment. The photosynthetic rate of wheat at jointing stage could rapidly recover to a normal level under different treatments for five days. The longer the treatment duration was, the more inhibited the photosynthetic rate of wheat and the slower the recovery. Waterlogging + low illumination had the greatest impact on the recovery process. When the waterlogging lasted for more than 10 days or waterlogging + low illumination for more than 15 days at booting stage, the photosynthetic rate could not recover to CK level, but for low illumination treatment, the photosynthetic rate could recover under different stress duration. Overall, our results can be used to evaluate the damage caused by waterlogging and low illumination, which improve the applicability of wheat growth model under agrometeorological disasters.

Key words: wheat, waterlogging, low illumination, plant height, chlorophyll, photosynthetic rate.