| With the global scarcity of water resources,drought has become an important factor limiting plant growth,and turnips are also limited by drought stress.Therefore,it is of great significance to screen the drought-resistant resources of turnip and reveal the response mechanism of turnip drought.In this experiment,drought resistance of 42 turnip varieties at seedling stage was studied,and the germplasm with strong drought resistance was screened.Pot and natural drought experiments were employed to the measurement of plant of growth and physiological indicators of turnip seedlings.The two screened turnip resources were treated with natural drought treatment of 0d,4d,7d,10 d and rehydrated for 2 days.experiments were employed to the measurement of plant photosynthetic fluorescence,stomata and osmoregulation,as well as antioxidantrelated substances and antioxidant enzymes.The conclusions reached are as follows:(1)There are five drought-tolerant varieties,25 medium-drought-resistant varieties and 12 droughtsensitive varieties at the seedling stage were screened.Among them,"WJC129" has the strongest drought resistance,and "WJC120" is the most sensitive to drought.A regression equation Y =-0.035 + 0.288X1 +0.077X2 + 0.132X3 + 0.011X4 + 0.336X5 for the preliminary prediction of drought resistance in turnip seedlings was established by stepwise regression analysis.At the same time,the indicators of drought resistance in turnips were also screened,with stem thickness,root to crown ratio,malondialdehyde and proline as the main indicators of drought resistance in turnip seedlings,and plant height,soluble protein and soluble sugar as secondary indicators.(2)Drought stress changed the appearance and morphology of turnip seedling plants,reduced the water potential and relative water content of turnip leaves,decreased chlorophyll content and photosynthetic fluorescence parameters,and increased the content of reactive oxygen species in cells,resulting in damage to the cell membrane structure of leaves.When the soil water content decreased to 54.56%,the droughtsensitive WJC120 turnip began to be subjected to drought stress.When the soil moisture content reached28.71%,the drought-resistant WJC129 just showed symptoms of drought damage.However,the soil water content decreased to 10.95%,and WJC120 turnip heart leaf was damaged and tended to die,while WJC129 heart leaf was not seriously damaged and could return to normal growth after 2 days of rehydration.Under drought stress,the leaf water potential,relative water content,chlorophyll content,net photosynthetic rate and maximum photochemical efficiency of drought-resistant turnip WJC129 were higher than those of drought-sensitive WJC120.The chloroplast structure of drought-sensitive WJC120 was damaged and severely inhibited by light,and its leaf cell membrane was damaged more than that of drought-resistant resource WJC129.(3)Turnip WJC129 has the appearance characteristics of drought-resistant plants,and its leaves are relatively small and the plant type is short,which can reduce water consumption and transpiration.Turnip can adjust the stomatal characteristic values to reduce transpiration,increase osmoregulatory substance content,increase antioxidant enzyme activity,and interact with related substances and enzymes in the ASAGSH cycle to resist drought.Compared with WJC120,WJC129 can reduce water dispersion loss by the waxy layer attached to the surface,thereby increasing drought resistance.When subjected to drought stress,the osmotic regulation substances of drought-sensitive WJC120 first peaked and then decreased at 7 d.The contents of soluble sugars,soluble protein and proline of drought-resistant WJC129 were higher than those of WJC120 on the 10 th day of drought.The SOD and CAT activities of drought-resistant WJC129 were high,while the POD activity of drought-sensitive WJC120 was higher.The ASA content of drought-resistant WJC129 was significantly higher than that of WJC120,and the APX activity of WJC129 increased significantly with the increase of drought days.However,the APX activity of WJC120 didn’t change significantly,but its MDHAR activity was significantly higher than that of WJC129.The results showed that the osmotic regulation and antioxidant regulation ability of WJC129 turnip were stronger than those of WIC120. |
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