Effects Of Soil Drought Stress On Cauliflower Quality And The Determination Of Disaster Indicators

The experiment used broccoli (Chonghua 120d) was conducted in the experimental greenhouse of NUIST to research the effect of drought stress. Four soil moisture treatments were designed, i.e., T1 ( 70%?80% of Field holding capacity),T2 (60%-70% of Field holding capacity) ,T3 (50%?60% of Field holding capacity) ,T4 (35%?45% of Field holding capacity) . The photosynthetic characteristics, chlorophyll content,fluorescence parameters, root activity and cauliflower soluble protein, soluble sugar, sucrose, organic acid, vitamin C and shape grade of cauliflowers were determined to to study the effects of drought stress. The main findings are as follows:(1) The results showed that the contents of chlorophyll a, chlorophyll b in cauliflower leaves were significantly decreased with the increase of treatment time under different drought stress. The maximum net photo- synthetic rate of leaves under the same treatment decreased with the increase of treatment time. The net photosynthetic rate of different treatment cauliflower under the same day showed T1>T2> T3> T4 during the experiment. The apparent quantum efficiency is reduced and the light compensation point is increased.(2) With the intensification of drought stress, the Fv/Fm, ETR and qP of cauliflower leaves decreased, and also decreased with the increase of drought duration, while the qN increased significantly under drought stress. The root activity of cauliflower decreased with the prolongation of stress duration under drought stress, and decreased with the increase of drought stress intensity.(3) Seedling drought stress inhibited the growth of cauliflower height and leaf area.The production of cauliflower decreased significantly under drought stress. 25 days of T4 treatment, the cauliflower single ball weight is only 404.18g. The content of soluble protein and vitamin C decreased and the content of organic acid increased.The content of soluble sugar and sucrose in the flowering of T2 and T3 drought stress increased first and then decreased with the prolongation of treatment time,peaked at 15 and 10 days of drought Respectively. Drought stress affects the quality grade of cauliflower, the more severe drought stress, the smaller the proportion of premium cauliflower,the higher the proportion of secondary cauliflower.(4) The content of vitamin C, the proportion of primary cauliflower, the weight of single ball, the activity of root and the net photosynthetic rate of cauliflower were significantly correlated with the change of soil water index. The drought stress index of cauliflower was calculated according to the drought stress index. By calculating the drought stress index of cauliflower, the drought grade of cauliflower was divided into three grades: light, medium, heavy and extremely heavy according to the drought stress index. And the drought grade of different drought stress was obtained.