Study On Compensation Effect Of Regulated Deficit Irrigation On Sugar Beet

[Objective]Under the climate condition of arid area,the experiment of regulating deficit irrigation was carried out in different growth stages of sugar beet under drip irrigation.The dry matter accumulation,leaf photosynthetic physiological characteristics,leaf morphological structure characteristics and yield and quality characteristics of sugar beet under regulated deficit irrigation were analyzed.The purpose of the experiment was to clarify the irrigation mode of regulating deficit in different growth stages of sugar beet under drip irrigation in arid area,and to reveal the water deficit of sugar beet in canopy development stage after water deficit was restored based on the assimilate distribution mechanism and photosynthesis response mechanism,the growth and physiological compensation effect of drip irrigation beet under regulated deficit irrigation was put forward in order to provide support for high yield and efficient water management of drip irrigation beet in Northern Xinjiang.[Methods]In 2014 and 2015,beta 356?Beta vulgaris L.?was used as the test material to set the field control experiment of 70%field capacity?70%FC?,50%field capacity?50%FC?and 30%field capacity?30%FC?respectively in canopy development,storage root development and sugar accumulation stage of sugar beet under drip irrigation,so as to clarify the irrigation mode of regulating deficit in different growth stages of sugar beet under drip irrigation.In 2017 and 2018,a pot experiment was conducted in the sensitive period of sugar beet?canopy development stage?with a lower limit of 70%FC,50%FC and 30%FC.The assimilate distribution mechanism and photosynthetic physiological mechanism of canopy development stage of sugar beet foliage under drip irrigation were determined by ¹³C isotope tracing technology and plant cytology.[Results]?1?Under regulated deficit irrigation,LAI was decreased in the canopy development and storage root development stage,and the accumulation time reached maximal accumulation rate of dry matter?T_m?was shortened,while Maximum accumulation rate?V_m?was increased.The yield of sugar beet was not affected.Compared with 70%FC,sugar beet yield,sugar content,sugar yield and irrigation water use efficiency?IWUE?in 2014 and 2015increased by 1-52%,7-11%,9-57%and 21-29%respectively under the treatment of 50%FC during the canopy development stage,increased by 24-90%,1-?-3?%,20-88%and 96-134%under the treatment of 30%FC during the storage root development stage,increased by46-52%,1%-9%,53-58%and 86-122%respectively under the treatment of 30%FC during the sugar accumulation stage,which indicated that the purpose of saving water and increasing production could be achieved by drip irrigation in different growth stages.?2?Regulated deficit irrigation significantly affected photosynthetic capacity,osmotic regulation capacity,membrane system and protective enzyme activity of sugar beet leaves.Compared with 70%FC,the net photosynthetic rate of leaves increased significantly at 50%FC and decreased significantly at 30%FC.Under the condition of regulated deficit irrigation,membrane permeability?malondialdehyde and relative conductivity?,antioxidant enzyme activity?peroxidase and catalase?and osmoregulation substance?proline and soluble sugar?of leaves changed significantly,among which malondialdehyde content,catalase activity and proline content were the most sensitive,indicating membrane permeability,antioxidant enzyme activity and osmoregulation of leaves material saving co controlled sugar beet to adapt to deficit irrigation.?3?Compared with 70%FC,the total fixed amount of ¹³C in 50%FC treatment increased before irrigation,while that in 30%FC treatment decreased.At the same time,the total fixed amount of ¹³C in both treatments increased while the total fixed amount of ¹³C in leaves decreased.After irrigation in 50%FC and 30%FC treatment,the total fixed amount of ¹³C in50%FC and 30%FC treatment decreased,and the distribution of dry matter in 50%FC and30%treatment was mainly root?63.26%and 53.39%?,but the fixed proportion of ¹³C of leaves and roots under 30%FC treatment increased?63%and-32%?compared with that before irrigation,which indicated that the assimilate allocation strategies were different in the canopy development stage of sugar beet leaves and roots under different deficit t irrigation treatments,among which 70%FC deficit irrigation treatment increased source and expand storage,50%FC deficit irrigation treatment maintained source and expand storage,30%FC deficit irrigation treatment maintained source and decreased storage.In addition,correlation analysis showed that?¹³C in leaves could effectively indicate WUEy.?4?Compared with 70%FC,the photosynthetic rate of sugar beet leaves treated with 50%FC before irrigation had no significant change,while that of 30%FC decreased significantly;there was no significant difference between the treatments after irrigation.The results showed that the photosynthetic rate of sugar beet leaves treated with 70%FC and 50%FC was mainly limited by the mesophyll before irrigation,while that of 30%FC was mainly limited by the stomatal.The main limiting factors of photosynthetic rate of sugar beet leaves treated with 30%FC were mesophyll after irrigation,which indicated that sugar beet leaves could adapt to the middle water shortage ring by adjusting stomatal conductance sugar beet leaves adapt to severe water shortage environment by changing leaf structure?increasing leaf and mesophyll thickness?.?5?Under the condition of regulated deficit irrigation,the growth and physiological indexes of beet under drip irrigation have some compensation effects,and the compensation effects are different in different growth periods.The compensatory effect of growth mainly occurred in the canopy development.At this time,except for the 50%FC treatment of LAI and 30%FC treatment of root shoot ratio did not produce compensatory effect,other indicators have compensatory effect.The physiological compensation effect in the canopy development stage is the compensation effect of malondialdehyde,relative conductivity and peroxidase in leaves,the compensation effect of relative conductivity and catalase in roots,the compensation effect of soluble sugar in leaves and proline in roots during the root storage development stage,which shows that deficit irrigation has a compensation effect on the early growth stage of drip irrigation sugar beet?canopy development stage?the compensation speed of growth and physiological index is fast,and the compensation degree of leaf physiological index under regulated deficit irrigation is greater than that of root,while the compensation speed of root tuber physiological index is better than that of leaf.[Conclusion]Under drought stress,the physiological activity of beet membrane system is firstly damaged.At this time,the degree of damage of beet leaves under severe drought stress is significantly higher than that under moderate drought stress.Sugar beet adapts to the damage by enhancing the protective enzyme activity,osmotic regulation and photosynthesis of leaves.After rewatering,the formation and distribution of the same chemicals change.The specific performance is that the treatment of moderate regulated deficit irrigation does not reduce on the basis of the assimilate,the distribution to the root was increased,while the heavy regulated deficit irrigation reduced the assimilate and increased the distribution to the leaves to adapt to the damage caused by water shortage.Finally,the compensation effect of sugar beet yield under different regulated deficit irrigation was realized.Therefore,under the premise of ensuring that the soil water content is not less than 70%FC in the period of non regulated deficit,supplementary irrigation can be carried out in the canopy development,storage root development and sugar accumulation stage in the arid area when the soil water content is reduced to 50%,30%and 30%FC respectively,which can reduce the irrigation amount and increase the yield at the same time,so as to achieve the goal of water saving,high yield and high quality.