Relationship Between Xylem Anatomical Structure And Hydraulic Function Of Kiwifruit With Different Ploidy Levels

Polyploidization is an important mechanism for speciation and evolutionary adaptation.Polyploidization has significant physiological and ecological effects on plant xylem structure and hydraulic function.Kiwifruit is a perennial woody vine with complex ploidy variation,and its polyploid population is distributed in high altitude areas.Drought and low temperature are the most important environmental factors that tightly correlates with plant growth in this area,which significantly affect the safe transportation of water in xylem.From the perspective of plant water physiology,this paper explored the effects of both drought and low temperature stresses on hydraulic conduction of different ploidy kiwifruits and their hydraulic recovery mechanism in spring,analyzed the overwintering water adaptation strategies of different ploidy kiwifruits,and determined the xylem anatomical characteristics to support them.The following results were obtained:1.There were significant differences in the anatomical structure of the xylem of different ploidy kiwifruit branches.Polyploid kiwifruit had larger average vessel diameter,hydraulic vessel diameter,vessel wall thickness and wood density,and lower vessel density at the vessel level.Polyploids have smaller intervessel pit membrane area,larger pit aperture shape and pit density at the pit level.2.Differences in hydraulic functions were underlain by divergences in xylem structural traits of different ploidy kiwifruits.The diploid kiwifruit with higher hydraulic conductivity has larger vessel density and intervessel pit membrane area.Polyploids with high hydraulic safety have small and narrow pit aperture shape,large vessel wall thickness and wood density.3.Hydraulic conductivity of diploid and polyploid kiwifruit declined sharply in winter and recovered in spring.Under the freeze-thaw stress in February,the water conductivity of kiwifruits lost 93.35-95.06%,and all ploidy levels showed vulnerability to freeze-thaw cycles.In spring,the occurrence of positive xylem pressure promoted the recovery of some hydraulic functions of kiwifruit,and the water conductivity of branches recovered to 70.24-89.36%.4.The overwintering water adaptation strategies of kiwifruit were different among ploidy levels.The diploid kiwifruit has high hydraulic conductivity in the growing season,but it is greatly affected by seasonal changes and has high vulnerability under drought and low temperature stresses,which belongs to the production strategy of efficient access to resources.Polyploid kiwifruit has low hydraulic conductivity in the growing season,and is less affected by seasonal changes.It has stronger tolerance under drought and low temperature stresses,which belongs to the conservation strategy of resource utilization.This study investigated the relationship between xylem structure and hydraulic function of different ploidy kiwifruit,we preliminarily revealed the adaptability differences of different ploidy kiwifruit to environmental changes,and deepened our understanding of the effect of polyploidization on plant adaptability under climate change conditions,which is of great significance to understand the mechanism of plant response to future climate change.