Study On The Factors Affecting Excised-leaf Water Retention Capacity In Flue-cured Tobacco

In order to check whether the hydraulic efficiency of blade can be used as an scientific reference indicator in drought resistance identification and variety breeding.The effect of leaf position,excised leaf dehydration time,and leaf age on leaf water retention capacity,meanwhile,the characteristics of leaf water retention at different developmental stages on flue-cured tobacco were studied using excised leaf natural dehydration method in Yuyan 6? Nongda 202 and K326 with different drought resistance.The results are as follows:(1)The effect of leaf position and excised leaf dehydration time on leaf water retention capacity were studied in two flue-cured tobacco varieties Yuyan 6 and Nongda 202.The results showed that there was no significant difference among different leaf positions.The antioxidant enzyme activity,soluble protein content and abscisic acid(ABA)content in excised leaves reached the maximum in vitro 24 hours,meanwhile,speed of malondialdehyde(MDA)growth became slow after 24 hours.The relative expression of four stress responsive genes(AREB,CDPK2,ERD10 C,LEA5)reached the highest level at 24 hours.The results showed that the physiological metabolism of excised leaves was strongest at 24 hours,and the difference in all sorts of indicators between two varieties reached the greatest at 24 hours.Therefore,there was little relationship between water retention capacity and leaf position in excised flue-cured tobacco leaves,and leaf water loss for 24 hours was the appropriate time to determine the water retention capacity in tobacco excised leaves.(2)The characteristics of leaf water retention at different developmental stages were studied in three flue-cured tobacco varieties Yuyan 6 ?Nongda 202 and K326.The results showed that variety,growth period and their interaction had significant effects on the water holding capacity withthe contribution rates reaching 63.09%,24.65% and 12.25%,respectively.The water holding capacity of leaves in three varieties was relatively higher at the late stage;The highest performance was Yuyan6 and the lowest was Nongda202 at the same development period.The characteristics of changes in hormone content,antioxidant enzyme activities,and relative stress resistance genes in 3 varieties at different developmental stages also confirmed that the genetic factors were the key factors affecting the water retention of the flue-cured tobacco leaves.(3)The effect of leaf age on leaf water retention were studied in three flue-cured tobacco varieties Yuyan 6 ?Nongda 202 and K326.The water retention capacity of the leaves at the 9th leaf position in 3 varieties was determined on the leaf age of 10 d,20d,30 d,40d and 50 d.The result shows that the water retention of leaf was increasing with the increase of leaf age.Besides,the chlorophyll extraction rate,which represents the development of stratum corneum,showed that with the increasing of leaf age,leaf cuticle gradually mature,leaf permeability also decreased.This might be one of the reasons why the blade water retention increased with leaf age.This study indicated that leaf water loss for 24 hours was the appropriate time to determine the water retention capacity of tobacco excised leaves;there was little relationship between water retention capacity and leaf position;with the increase of leaf age,the water retention of leaf was increasing.Besides,the water retention of flue-cured tobacco leaves was related to the genetic factors and the developmental stages of leaves.In addition,the genetic factors were the key factors affecting the water retention of the flue-cured tobacco leaves.Thus,when applying the hydraulic efficiency of blade as an scientific reference indicator in drought resistance identification and variety breeding only in the same environmental conditions,the same development period and the same leaf position,the same leaf age leaves,the blade water retention could reflect their ability of resistance to drought in different materials.