Effects Of Drought Stress And Rehydration On The Growth And Fruit Quality Of Blue Honeysuckle (Lonicera Caerulea L.)

The experiment was conducted in 2021～2022 at the Northeast Agricultural University Small Berry Germplasm Resource Nursery,using blue honeysuckle’Lan Jingling’as the test material and artificially simulating drought stress using the natural drought method in pots,with four soil drought stress gradients of 60%～80%（CK）,50%～55%（mild stress）,35%～40%（moderate stress）and25%～30%（severe stress）.The experiment aims to study the physiological changes of blue honeysuckle under drought stress,to explore the effects on the physiological characteristics and fruit quality of blue honeysuckle under different drought stress and after rehydration,to enrich the theory of blue honeysuckle adversity physiology,and to provide theoretical basis and technical support for the zoning of blue honeysuckle growth and practical production,the main conclusions are as follows:（1）Differential effects of different levels of drought stress on photosynthesis in blue honeysuckle leaves.With the increase of drought,the photosynthetic rate,transpiration rate and stomatal conductance of’Lan Jingling’leaves showed a decreasing trend,and the photosynthetic rate differed significantly under severe stress at the 11th day of stress,which was 42.6%lower compared with CK.The CO₂ concentration and SPAD showed an increasing trend,and with the extension of the rehydration days,the overall trend showed an increase and then a decrease,but still did not return to normal levels.The photosynthetic rate was still 1.3%higher than that of CK under severe stress at the 15th day of rehydration,indicating that’Lan Jingling’had a strong recovery ability to drought;the initial fluorescence（F₀）of’Lan Jingling’showed a decreasing trend,and the maximum fluorescence（F_m）showed a rising and then decreasing trend,and still did not return to normal level after rehydration.（2）The conductivity and malondialdehyde content of’Lan Jingling’leaves increased significantly with the increase of drought,and showed a trend of increasing and then decreasing with the extension of rehydration days,and did not return to normal level after rehydration.The relative conductivity increased significantly by 107.5%at the 17th day of stress compared with CK for mild stress,and by 54.5%and 107.5%at the 8th day of treatment for moderate and severe stress,respectively,compared with CK.At the 15th day of re-watering,the difference was 29.2%,20.8%and 32.8%respectively compared to CK.（3）The effects of different degrees of drought stresses on the content of osmoregulatory substances in blue honeysuckle leaves were different.With the increase of drought,the content of proline,soluble protein and soluble sugar in’Lan Jingling’leaves showed an increasing trend;with the extension of rehydration days it showed an increasing trend and then a decreasing trend;it did not return to normal level after rehydration.Soluble protein increased by 150.6%,249.4%and316.8%,respectively,compared with CK at the beginning of the stress;8.4%,40.9%and 41.9%,respectively,compared with CK at 15 d of rehydration;proline increased by 22.7%,15.8%and9.3%,respectively,compared with CK at the beginning of the stress;the difference between CK and CK at 15 d of rehydration The difference with CK at 15 d was 10.5%,8.7%and 12.2%,respectively,indicating that the osmoregulatory substances of’Lan Jingling’recovered faster from light stresses and slower from moderate and severe stresses after rehydration.（4）The effect of different degrees of drought stresses on the antioxidant defence system of’Lan Jingling’differed.The SOD activity of’Lan Jingling’leaves increased significantly with the increase of drought level,and the difference between severe stress and CK was significant at the 8th day of stress,and reached the highest level at the 17th day of stress,which was 134.0%higher than that of CK;after rehydration,it was still higher than that of CK,and SOD increased at the 15th day of stress,which was 1.1%and 3.0%higher than that of CK,respectively.SOD increased by 1.1%,3.7%and 9.6%at the 15th day of stress,but not significantly,the physiological regulation mechanism of the antioxidant defence system in’Lan Jingling’in response to drought stress and rehydration was revealed.（5）The effects of different degrees of drought stresses on the reactive oxygen species of blue honeysuckle were different.The superoxide anion and hydrogen peroxide contents of’Lan Jingling’leaves showed an increasing trend with the increase of drought,and the greater the degree of stress,the more significant the increase;the rehydration showed a decreasing trend,but did not return to the normal level.At the 20th day of treatment,the superoxide anion content in the cells of’Lan Jingling’leaves under severe stress reached the highest level,increasing by 48.5%compared with CK.The H₂O₂ content in the cells of’Lan Jingling’leaves under severe stress reached its highest level on the 8th day of treatment,increasing by 78.2%compared to CK,and then leveled off,but was significantly higher than in the CK.At 15 d of rehydration,H₂O₂ increased by 13.8%,15.1%and 28.4%compared with CK;after rehydration,the change in H₂O₂ content gradually levelled off,but was still significantly higher than CK and did not return to normal levels.（6）Rehydration after drought stress had some effect on’Lan Jingling’fruit quality,improving the intrinsic quality of’Lan Jingling’fruit,but inevitably causing a decrease in its extrinsic quality.Most of the extrinsic quality indicators were significantly lower than CK under mild drought stress,but most of the intrinsic quality indicators were higher than CK under mild drought stress.Although there was a negative impact of drought stress on the physiological indicators of’Lan Jingling’,this impact was not irreversible as the effects of mild stress on’Lan Jingling’recovered to some extent after re-watering.