Water Use Characteristics Of Dendrocalamus Latiflorus Munro With Different Ages During Two Phenologies

Bamboo originated in Southeast Asia,mainly distributed in tropical and subtropical regions.Without secondary growth,bamboos will keep physiological function of the vascular bundles in the culms bundles over the whole life.There will be more tyloses and depositions in the transport system tubes,which might reduce the hydraulic conductivity of the culm,and resulting in the difference of water use of bamboo with different ages.In addition,phenology is also a factor affecting water use of bamboo.Differences in water use efficiency,therefore,are expected at different phenological stages of bamboos.For those reasons,we aim to understand the water use characteristics of bamboos of different ages and phenology.This study can help us to understand the physiological process of bamboo,and thus provides a theoretical and scientific basis for the cultivation and management of bamboo forests.We selected Dendrocalamus latiflorus of different ages at Xinping Yi and Dai Autongomous Country,Yuxi City,Yunnan Province as study materials,and in situ monitoring to explore how age and phenology affect the transportation and replenishment of the culm;how the stem sap flow of Dendrocalamus latiflorus at different ages respond to environmental factors;and how the stem hydraulic characteristics of Dendrocalamus latiflorus at different ages coordinate with the canopy physiology,so as to jointly determine the water use characteristics of Dendrocalamus latiflorus at different ages.Our research showed that:(1)Influenced by the increase of age and the decrease of hydraulic conductivity of conduit,the order of sap flow density and diurnal water consumption of Dendrocalamus latiflorus was 1-year-old > 3-year-old > 5-year-old after growing leaves,while the order of stem sap flow density and diurnal water consumption was3-year-old ≥ 5-year-old > 1-year-old before growing leaves,but no matter before or after growing leaves,the water demand of 1-year-old Dendrocalamus latiflorus was the highest because of the leaf transpiration was the main factor driving the stem sap flow.(2)The changes of photosynthetically active radiation(PAR),saturated water pressure deficit(VPD)and stem sap flow at different ages in the two phenological phases were single peak-day,and the day high night low.Both phenology and age affected the sensitivity of the stem sap flow of Dendrocalamus latiflorus to PAR andVPD,but the stem sap flow responded more strongly to the VPD.Furthermore,due to the differences in storage water use characteristics,phenological characteristics,and environmental factors,there was a hysteresis between the maximum daytime sap flux density and the VPD and PAR peaks of bamboo culms at different ages.(3)In the two phenological stages,there were differences between the canopy physiology of Dendrocalamus latiflorus at different ages,and the hydraulic characteristics were related to the leaf water potential,leaf hydraulic conductivity,net photosynthesis and stomatal conductivity.The efficiency of stem water transport played an important role in maintaining the net photosynthetic rate of the canopy.Compared with 1-year-old and 3-year-old Dendrocalamus latiflorus,5-year-old Dendrocalamus latiflorus showed more anisohydric behaviour.Different age of Dendrocalamus latiflorus showed different water regulation behaviors due to different physiological characteristics,but there was a coordination between canopy physiology and stem hydraulic characteristics,which jointly determined the water use characteristics of the whole Dendrocalamus latiflorus at different phenological stages and different ages.In this study,the water use characteristics of Dendrocalamus latiflorus with three age levels(1-year-old,3-year-old and 5-year-old)were monitored during the two different phonological periods(non-leafing and leafing-well).The variation of sap flux density,water consumption and the response of sap flow to major environmental factors were revealed in different phenological stages of Dendrocalamus latiflorus with three ages.The coordinated relations between hydraulic characteristics and physiological of bamboo canopy were also investigated.This study could not only provide a basis for the extensive knowledge about physiological and ecological adaptability of bamboos,but also assist the scientific management and sustainable utilization of Dendrocalamus latiflorus.