The Effect Of High Temperature Stress On Organ,Pollen And Flowering Period Of Different Jujube Varieties

This study was conducted in the jujube variety resource garden of the fruit tree experimental garden of the Forestry and Gardens Institute of the Xinjiang Academy of Agricultural Reclamation Sciences in2022,using four different jujube varieties as test materials,namely,‘Superior Early-Maturing’,‘Jixin Jujuba’,‘Buluosu’,‘Fengmiguan’.Before and after the bud stage,warming treatment was carried out by putting up a shed.In addition to the control group,a total of three temperature treatments(H1:38～39℃,H2:41～42℃,H3:44～45℃)were set up.This paper mainly studied the effect ofhigh temperature stress on the flower organs of different jujube varieties at the bud stage,and analyzed the changes of nutrient content and hormone content in their flowers,and conducted in vitro culture test and pollen germination test at high temperature to study the effect of high temperature stress on the flower organs and pollen germination after flowering,and comprehensively analyzed the heat resistance performance of various varieties under high temperature stress.The research results are as follows:(1)After high temperature treatment at 39 ℃ and above at the bud stage,the flowering time of the four varieties was advanced,the flowering time was shortened,and the flowering quantity was significantly decreased,and the phenomenon of falling flowers was serious.Among them,the variety of Jixin jujube changed most stably when it was exposed to high temperature,and the flowering amount was basically at the same level as the control group under 39 ℃ treatment.(2)After high temperature treatment in bud stage,different flower organs of different varieties developed poorly,and their development generally showed a trend of "the higher the temperature,the smaller the flower organs".The pistil length,filament length,corolla diameter and nectar disc diameter of the‘Superior Early-Maturing’were significantly different from those of the control group under high temperature stress;There was no significant difference in the external characteristics of the flower organs between the‘Fengmiguan and the control group except for the length of the filaments.(3)The pollens of various jujube trees have shrunk to different degrees under the high temperature treatment at the bud stage.The general performance is that with the increase of the treatment temperature,the length of the polar axis and the equatorial axis of the pollens shorten,the ratio of the polar axis to the equatorial axis increases,and the degree of pollen deformity increases.At the same time,the relationship between pollen germination rate and pollen viability is roughly "the higher the temperature,the lower the germination rate and viability".In the experiment of Jixin Jujube,the germination rate of H1,H2 and H3 decreased by 36.64%,39.13% and 71.18% respectively compared with CK;In the experiment of ‘Buluosu’,it was found that the germination rate of treatment H1,H2,H3 was 17.33%,37.73% and 82.13% lower than that of control CK,respectively.The inhibition effect was significant and there were significant differences among the treatments.Although the germination rate of‘Superior Early-Maturing’is relatively low,it is less affected by temperature within 38-42 ℃,while the germination rate and viability of‘Buluosu’pollen maintained a higher level than other varieties under various high temperature treatments.(4)The content of sucrose,glucose and soluble protein in jujube flower mainly showed a trend of decreasing or rising first and then decreasing with the increase of temperature treatment degree.The nodes that rose first and then decreased were all at 38～39 ℃.The sugar and glucose contents of Jixin Jujube and‘Buluosu’flowers are basically similar to those of high temperature,showing a trend of rising first and then falling.The content of sucrose,glucose and soluble protein in the flower of the‘Buluosu’with the highest pollen germination rate is higher than that of other varieties in most cases.(5)In this study,the content of endogenous hormones in different varieties of jujube flowers was significantly affected by high temperature stress,and under different temperature stress,the change of endogenous hormones in different varieties was more obvious.Under high temperature treatment,the content of IAA,GA3 and CTK in the‘Superior Early-Maturing’flowers decreased,and the content of ABA increased;The contents of GA3 and IAA in Jixin Jujube increased first and then decreased,while the contents of CTK and ABA decreased;The contents of CTK and IAA in‘Buluosu’increased first and then decreased,while the contents of GA3 and ABA decreased;The content of GA3 in‘Fengmiguan’first decreased and then increased,the content of CTK and IAA first increased and then decreased,and the content of ABA increased.Compared with the control group,the content of CTK in the flower of‘Buluosu’significantly increased and the content of ABA significantly decreased,which was significantly different from other varieties.(6)The in vitro culture test showed that after flowering of jujube trees,high temperature stress also had a significant impact on the flowers of various varieties of jujube trees,and its main manifestations were the shortening of pistil length and filament length,and the significantly shrinking of corolla and nectar disc size compared with the control group,and the degree of shrinkage was positively correlated with high temperature and treatment time.(7)The high temperature treatment during pollen germination had no significant effect on the pollen size of‘Jixin Jujuba’,‘Buluosu’and‘Fengmiguan’,but the pollen morphology of‘Fengmiguan’was deformed and the ratio of polar axis to equatorial axis changed significantly under 45℃/2h treatment.High temperature had a significant effect on the size of Superior Early-Maturin pollen,and the pollen size under42 ℃/2h and 45℃/2h treatments was significantly smaller than that of CK.The pollen germination rate and pollen tube length of the four jujube varieties were significantly inhibited.The pollen germination rate of each high temperature treatment was significantly lower than that of the control CK.The pollen did not germinate under the treatment of 42 ℃/2h and 45 ℃/2h for Superior Early-Maturin and ‘Fengmiguan’,and the pollen did not germinate under the treatment of 45 ℃/2h for‘Jixin Jujuba’and‘Buluosu’.The germination rate of‘Buluosu’kept a higher level than other varieties under various high temperature treatments.