Response Of Vegetable In Greenhouse To Deficit- Re-Water Alternative Irrigation And The Best Irrigation Mode

The series of experiments carried out during 2012 to 2014, using greenhouse muskmelon, greenhouse cucumbers, pot cucumbers and pot watermelons as research objects to find response of growth, physiology, water consumption, yield and fruit quality of vegetables under different threshold about deficit- compensation alternate irrigation, and to analyze different index using principal component analysis method(PCA). We mainly obtained the following results:(1) There was no significant change about vine length and stem diameter of greenhouse muskmelons and cucumbers under light deficit compared to CK, but both of them decreased under severe deficit, while vine length and stem diameter of pot cucumbers and watermelons decreased under both light and severe deficit. Vine length and stem diameter recovered significantly after re-water under severe deficit, and increased first, then decreased with compensation water. CK of greenhouse muskmelons was the first treatment to enter the fruit growth stage, and the diameter of fruit decreased with deficit and increased with compensation. Root length decreased with irrigated water, and it increased first, then decreased with compensation of greenhouse and pot cucumbers, while decreased with deficit and compensation of pot watermelons. Root dry weight of all experiments decreased with irrigated water after a long time, but increased with compensation, and showed overcompensation after high compensation irrigation. Shoot dry weight decreased and ratio of root to shoot increased with irrigated water, and ratio of root to shoot increased significantly after re-water, and increased with compensation.(2) There was no significant change about stomatal conductance of greenhouse muskmelons under light deficit compared to CK, but it decreased severely under severe deficit, while stomatal conductance, photosynthetic rate and transpiration rate of cucumbers and watermelons decreased with deficit. Stomatal conductance recovered significantly after re-water, and increased first, and then decreased with compensation. Photosynthetic rate and transpiration rate recovered after re-water at the same time, and photosynthetic rate decreased and transpiration rate increased with compensation. WUE of leaves increased with deficit and decreased with compensation. Chlorophyll of pot cucumbers and watermelons increased with deficit under the certain range, but decreased under severe deficit and it increased after re-water compared to CK. Proline of pot cucumbers and watermelons increased significantly after severe deficit, but decreased with compensation, and there was no significant change compared to CK under the same compensation water and different deficit. MDA decreased after re-water, and showed no significant change compared to CK. Root vigor was high after continuous deficit – compensation irrigation, and decreased with compensation.(3) Yield of greenhouse muskmelons and cucumbers decreased with deficit, but Irrigated Water Use Efficiency(IWUE) increased at the same time. Yield increased significantly after re-water under severe deficit. Yield and IWUE of greenhouse muskmelons increased with compensation, while the same of greenhouse cucumbers decreased. Accumulation of yield of greenhouse cucumbers showed exponential growth the first 20 days after the begin of harvest, and showed parabolic growth after 20 days. Soluble solid, soluble sugar and soluble protein increased with deficit, organic acids decreased at the same time. Vitamin C of muskmelons and watermelons decreased and it of cucumbers increased with deficit. Soluble solid and soluble sugar decreased with high level of compensation, but there was no significant change of vitamin C among all treatments.(4) Taking greenhouse muskmelon, cucumber and watermelon into PCA, we found that after severe deficit, fruit quality of muskmelons and cucumbers showed the best, and the difference of quality among other deficit and re-water treatments was not significant. The qualities of muskmelons and cucumbers rose and dropped respectively with compensation. In the condition of same amount of re-water, the quality of muskmelon and cucumber increased with deficit.Severe deficit- low and moderate re-water treatments had the best quality results in all deficit and re-water treatments. Taking both yield and quality into consideration unsing PCA, we found the results of muskmelon and cucumber dropped with compensaiton. In the condition of same re-water treatment, the results of muskmelon and cucumber in PCA got better with deficit. The yield and quality results of greenhouse muskmelons and cucumbers were better under severe deficit and re-water treatments than other treatments, and the result of low re-water after severe deficit treatment was the best.