Photosynthetic Characteristic To Dehydration,Rehydration And Low Temperature In Different Evolutionary Species

Plants always suffered from drought,low temperature,salt damage and other environmental stress.Plants formed a variety of responses to adapt to adverse environment,and minimize the harm.Whether there are differences in stress resistance among different evolutionary plant species is a major scientific issue.We examined two fern species,which are Matteuccia struthiopteris(L.)Todaro and Coniogramme japonica(Thunb.)Diels,and two gymnosperm species,which are Ginkgo biloba L.and Metasequoia glyptostroboides,to reveal the differences in leaf water potential,photosynthetic characteristics and leaf hydraulic conductance during dehydration and rehydration.Then we examined two fern species,which are Matteuccia struthiopteris(L.)Todaro and Nephrolepis auriculata(L.)Trimen and two angiosperm species,which are Fragaria ×ananassa Duch and Helianthus annuus L.,to reveal their response to temperature variation and recovery ability.The results show:1.The stomatal conductance of ferns declined with the falling of leaf water potential and showed a rapid recovery with the rise of leaf water potential during the process of dehydration and rehydration.Two fern species exhibited a passive stomata behavior driven by water potential.Two gymnosperms species were found to show a liner depression between stomatal conductance and water potential during water stress,while a hysteresis in the relationship between water potential and stomatal conductance as rewatered plants recovered from water stress.It indicated the passive control and active control both exist in gymnosperm stomata behavior.2.Two ferns showed a weak ability to maintain leaf hydraulic conductance.Water potential maintained high when it lost 50% of leaf hydraulic conductance.Leaf hydraulic conductance could show a rapid recovery during rehydration while water potential and stomatal conductance could recover synchronous.Two gymnosperms exhibited a strong ability to maintain leaf hydraulic conductance.Water potential were low when it lost 50% of leaf hydraulic conductance.Leaf hydraulic conductance couldn't show a rapid recovery during rehydration and a hysteresis in the relationship between stomatal conductance and leaf hydraulic conductance.Leaf hydraulic conductance in two fern species showed a liner relationship with stomatal conductance by a depression in water stress and a rapid recovery in rehydration.Gymnosperms could maintain leafhydraulic conductance during dehydration and showed a hysteresis during recovery.Leaf hydraulic conductance in two gymnosperms species did not exhibit a liner relationship with stomatal conductance.Gymnosperms showed a higher water use efficiency in both dehydration and rehydration than ferns'.3.The photosynthetic rate,stomatal conductance and transpiration rate of ferns and angiosperms declined with the falling of temperature.The photosynthetic rate of ferns was sensitive to chilling,and showed a rapid depression with the temperature reduction.While the photosynthetic rate of angiosperms was not sensitive to chilling,and showed a slow depression with the temperature reduction.The stomatal conductance of ferns lacked sensitivity to chilling,while the angiosperms were sensitive to temperature depression.The transpiration of both ferns and angiosperms showed similar responses to chilling.The water use efficiency of ferns could drop with the temperature reduction,while the angiosperms' only drop when the temperature drop to a certain degree.4.The photosynthetic rate,stomatal conductance and transpiration rate of ferns and angiosperms showed a rapid recovery with the rise of temperature,while the ferns' couldn't.However,the stomatal conductance of ferns could recover faster than the angiosperms'.The responses of transpiration to the rise of temperature were similar between ferns and angiosperms.