The Comparison On Salt-collecting、Salt-secreting And Photosynthetic Gas-exchanging Ability Among Leaves At Different Positions On The Stem Of Glycyrrhiza Uralensis

The normal maintain of stomatal opening-closing regulating function is the key to the healthy growth of the plants.Early research found that stomata and salt gland of ural licorice living in high salt habitat were able to secrete salt,In theory,salt crystals secreted may clog pores,may have a bad effect on the normal regulation of stomatal opening,plant’s photosynthesis,growth and development,but the licorice did not show obvious suffer symptoms.Thus,there must be some kind of compromise between those two kind of behavior,gas exchange and salt-secretion,to solve conflicts of interest.This paper assumes that stomata from different leaves of uralensis share the division of labor between salt-secrete and the gas exchange.The stoma-salt-secreting condition 、 Chlorophyll content 、 physiological regulatory mechanisms(photosynthetic physiological secondary metabolism、ion balance and osmotic adjustment、antioxidant enzyme system)、 leaves anatomical structure and ultrastructure were compared among different leaves of G.uralensis.Based on the above research to reveal the adaptation mechanism of ural licorice which growth in the high salt environment,and provided new scientific basis theory for salt tolerance mechanism.The main conclusions were as follows:1.Compared with the upper and middle leaves’ stomata,the lower leaves’ stomata were of the strongest salt secretion ability,secondly were the middle leaves’ stomata.There were no salt accumulations at the upper leaves’ stomata.The leaves’ photosynthetic ability in the upper leaves was the highest,the lower of leaves’ photosynthetic capacity is weak,and the middle leaves taken the second place.Thus concludes the upper leaves’ stoma are mainly used for gas-exchanging of photosynthetic in the main process of plant growth,hardly secret salt,and the lower of ural licorice leaves’ photosynthetic capacity is weak,the stoma is mainly responsible for put the excess salt out of the body,in order to maintain ion balance.So the division of labor and collaboration of different parts of the leaves achieve a clever trade-off between the two interest-conflicting behaviors: stomatal salt-secreting and photosynthetic gas exchange,which is an adaptation strategy of G.uralensis to the high salt environment.2.Chlorophyll fluorescence signal contains abundant photosynthesis information,is an important means to explore plant photosynthetic function.The chlorophyll fluorescence parameters at different leaves of uralensis were also different.The maximal photochemical efficiency of PSII(Fv/Fm),the potential photochemical efficiency of PSII(Fv /F0),the actual photochemical efficiency of PSII(ΦPSⅡ),the relative rate of electron transport(ETR)and the photochemical quenching coefficient(qP)in the upper leaves were the highest,the middle leaves were followed and the lower leaves were the weakest.The non-photochemical quenching coefficient(NPQ)showed an opposite direction.3.The content of Na+ in the lower leaves were the highest,it resulted the highest salt stress level in the lower leaves,the upper leaves under weakest salt stress level.The content of K+ were highest in the middle and lower leaves,which can reduce the ion damage caused by salt stress.The contents of Ca2+、Mg2+ 、soluble sugar and soluble protein,MDA,Pro and the activities of SOD、POD and CAT in the lower leaves were the highest,and those in the upper leaves were the lowest.So the leaf-salt-secreting ability amongdifferent height of leaves,with different salt stress level,was significantly different.So it was the effective way to avoid salt hurt for G.uralensis living at the severe salty habitat that stoma or gland on the leaves could secret salt out of its body,the leaves could effectively accumulate osmotic substances and significantly increase protective enzyme activities to adapt its salty environment.4.The leaves anatomical structure and ultrastructure were also compared among different leaves of G.uralensis.The results showed that the upper leaves’ mesophyll cells arranged the densest,the palisade tissue density is the largest,the middle leaves taken second place,the lower leaves’ mesophyll cells arranged loose.The leaf ultrastructure also has significant differences at different leaves of uralensis.The structural of chloroplast and mitochondria were integrally at the upper leaf and the starch grain number was the lowest.The structural of chloroplast at the middle and lower leaves were seriously distorted and contain lots of starch grain.All the mitochondria’s structure were integrally,but the cristae were indistinct at the there different leaves of G.uralensis.