Heterogeneity Response Of Photosynthesis Of Leaves Of Different Leaf Forms In Asplenium Under Water Stress

Asplenium,has various leaf shapes,and is an ideal material for studying leaf polymorphism.Observed from the wild,different leaf forms of Asplenium are different in morphological response under drought stress,and the manner in which the pinnate divided species adapt to drought is very similar to the compound leaf species of seed plants.To address this issue,this study used chlorophyll fluorescence imaging technology to study the photosynthetic heterogeneity of leaves of different leaf forms to explore the relationship between leaf morphology and photosynthetic physiological heterogeneity response in different environments.In this paper,the Asplenium is used as the research material.By comparing the morphological traits,functional traits and light response characteristics of the leaves of simple leaf and pinnate divided species of the Asplenium,to explore the heterogeneous responses of different leaf form species to different habitat water conditions.Water control experiments were carried out to determine the projected area of leaves and leaf photosynthetic spatial changes of simple leaf and pinnate divided species during water stress and rewatering,and explore the heterogeneity of different leaf formed species morphological structure and photosynthetic physiology on water changes response.It reveals the water resource utilization strategies and physiological and ecological adaptability of different leaf formed Asplenium species to obtain maximum photosynthetic productivity.The results show:(1)The leaf traits of different leaf formed species of Asplenium are significantly different.The simple leaf species exhibits thicker leaves,higher leaf succulence,and lower leaf dry matter content;the one pinnate divided species exhibits more leaf teeth and leave lobes,higher leaf dry matter content.There were significant differences between the two pinnate divided species.The combination of leaf traits of the Asplenium prolongatum Hook.favored the simple leaf species,while the Asplenium varians Wall.ex Hook.et Grev.preferred the one pinnate divided species.The leaf traits of different leaf formed species of Asplenium are significantly different.(2)The simple leaf species is a shade plant with a low light compensation point,net photosynthetic rate,dark respiration rate,and has a strong ability to use weak light;the one pinnate divided species is a sun plant with a large net photosynthesis rate,the larger light saturation point and make the use of strong light stronger.There were significant differences between the two pinnate divided species.The photosynthetic characteristics of the A.prolongatum favored the simple leaf species,while the A.varians was biased towards the one pinnate divided species.(3)During water stress and rewatering,there are obvious inter-species differences in the structural changes of different leaf forms of Asplenium.The simple-leaf species had significant differences among species.During the water change process of Asplenium griffithianum Hook.,the leaf curling degree was the smallest and the area reduction rate was the smallest;while the leaf curling degree of Asplenium ensiforme Wall.ex Hook.et Grev.was the largest and the area reduction rate was the largest.The leaf curl degree of one pinnate divided species was greater than that of the two pinnate divided species,and the area reduction rate was the same.After rehydration for 12h,except the Asplenium prolongatum Hook.all were recovered.(4)In the process of water stress and rewatering,the results of chlorophyll fluorescence imaging pictures of different leaf formed species of Asplenium show that F_v/F_m and NPQ have high degree of spatial heterogeneity in leaves,F_v’/F_m’and F_q’/F_m’were low degree of spatial heterogeneity in leaves,and there is no regular spatial water loss behavior.The stressed area of simple leaf species gradually expanded from the edge of the leaf to the main vein of the leaf;the stressed area of the one pinnate divided species was not uniform,and all the blades at the base or tip were seriously damaged,while the blades at other parts of the leaf undamaged;when the stress level of the two pinnate divided species is low,some of the feathers are damaged,but the difference between the two species is significantly different.(5)In the process of water stress and rewatering,the damaged area ratio of chlorophyll fluorescence parameters F_v/F_m,F_v’/F_m’,F_q’/F_m’increases with the increase of water stress.At a water loss rate of 60%,the proportion of damaged areas of simple leaf species is larger;The proportion of damaged areas of the one pinnate divided species is the smallest,and there are still some feathers that can carry out photosynthesis normally under severe stress.The two species of two pinnate divided species is significantly different and inconsistent,and there are higher photosynthetic heterogeneity.When the water loss rate reaches 10%,the ratio of the chlorophyll fluorescence parameter NPQ damaged area decreases with the increase of the degree of water stress;thereafter,the ratio of the NPQ damaged area shows different degrees of increase with the increase of the stress level.The proportion of damaged areas of the one pinnate divided species is smaller than that of simple leaf species.After 12 hours of rewatering,the damaged area was recovered to a greater extent,and the proportion of the damaged area of the one pinnate divided species was smaller than that of the simple leaf species.In summary,our research shows that the regulation ability of the PSⅡreaction center of the one pinnate divided species during water stress and rewatering is better than that of simple leaf species.Furthermore,the one pinnate divided species is more drought-tolerant than simple leaf species.The photosynthetic heterogeneity responses of two pinnate divided species was significantly different.The drought tolerance of the mutant A.varians was stronger than that of the simple leaf species,but the drought tolerance of the A.prolongatum was weaker than that of the simple leaf species.The research results are consistent with the hypothesis(1)The pinnate divided leaves improve the range of species water adaptation,but the current research results still cannot confirm the hypothesis(2)in the pinnate divided leaves,the higher the degree of division,the wider the range of water adaptation.Further research is still needed to verify.