The Physiological And Ecological Mechanism Of Root Zone Temperature/Root Regulating The Response Of Grapevine To Frost

Frost is an important disaster that affects the production and quality of grapevine.In recent years,due to the intensification of climate change,the frequency and intensity of frost has been increased significantly,which caused an increasing threat to grape and wine industry.It is urgent to strengthen the study mechanism of frost injury.In practice,many cultural techniques can be used to cope with the problem of frost.However,most of the techniques aim at improving the ambient temperature of plant or improving the anti-freeze ability of the fresh organs upground by a physical or chemical way.Less attention were paid to the role of root zone temperature and root played in the response of plant to low temperature stress.In fact,during the process of growing and development for plant,root plays not only a role of fixing and supplying of nutrient,but also serves as the"brain"of plant,to feel the changes of soil environment and regulate the function of whole plant to make a positive response to stress.In this thesis,the roles of root and root temperature played in the response of leaf to frost were measured and the physiological and ecological mechanisms were studied using grape as material.The main results are as follows:1.The sccumulation of soil effective accumulated temperature could be regulated by ridging or covering felt.The relationship between soil effective accumulated temperature,air effective accumulated temperature and the bud burst process of grapevine were analyzed.The results showed that,there were significant positive correlation between the soil effective accumulated temperature,the air effective accumulated temperature and the bud burst process of grapevine.The soil and air effective accumulated temperature participate in the budburst process together.Thedemand for soil effective accumulated temperature was 2-3 times of air effective accumulated temperature for grapevinebudburst.The budburst process could be delayed 3.5-5.5 days by ridging or covering felt,which was of value to prevent grapevine from the frost damage in the period.2.Two different root zone temperature?20?and-0.2??were set for grapevine during frost treatment.The resistance of leaf to frost and low temperature was regulat ed by the root zone temperature during frost.A lower root temperature?-0.2??cause d a severe frost damage to leaves and a higher root temperature?20??was conduci ve to reduce the frost damage for grapevine leaves,leading to a significant decrease i n the frost index by 53%.3.Frost and root freezing induced dehydration to leaves,resulting an increase of NO₃^-in leaf?2.24 folds of that in control?.The enrichment of NO₃^-inhibited COA res piration route in leaf,leading to the leakage of electronic and the burst of reactive ox ygen system,which could be an important reason for frost injury.The leaves of high r oot zone temperature treatment had relative higher POD and CAT activities,and lower activity of hydrogen peroxide than that of control.Under high root zone temperature condition,the responsing time and the trend of ABA concentration in leaves were co nsistent with the change of POD and CAT activities.Exogenous ABA can maintain th e activities of POD and CAT at a higher level under low temperature condition,whic h reduced the content of hydrogen peroxide in leaves.4Under different root zone temperature and frost conditions,metabolites in leaf w ere quite different.The most significantly changed metabolic pathway was the tricarbo xylic acid cycle?TCA?under high root zone temperature?20??,and changes of glycin e,serine and threonine metabolism weresignificantly changed at low root zone tempera ture?-0.2??.5.Seedlings were incubated with different light intensity at 25?after COLR/fro st treatment to analyze the effect of light intensity on photochemical activity.The wer e no significant differences in the final performance of frost symptoms under light co ndition or not for the injured leaves.However,the light intensity after frost affected t he recovery of photosynthetic property for unfrozen leaves.Shading was conducive for F_v/F_m to recovery in a long period without light inhibition,however caused a significa ntly decline in?_PS?;under moderate light intensity,F_v/F_m could be quickly restored to the normal level by increasing photochemical quenching?qP?and heat dissipation?N PQ?to improve the light using efficiency and the removal ability for excess energy,p romoating the recovery of?_PS?;high light intensity was conducive to recover F_v/F_m pa rtly,however led to light inhibition.500-600?mol·m^-2·s^-1 was considered as the best light intensity for leaf to recovery after frost.6.Root plays a similar role as“brain”in the response of up-ground tissues to str ess,as a result,it can be called“root brain”of plant.