Characteristics Analysis of Photosynthetically Active Radiation of Cotton Canopy under Different Water Treatments

【Objective】This project aims to study the variational characteristics of absorbed photosynthetically active radiation(APAR) and fractional interception of absorbed photosynthetically active radiation(FAPAR) of cotton canopy with different water treatments at growth stages and provide a theoretical evidence for real time,nondestructively and rapid monitoring the growth status of cotton.【Method】Cotton Xinluzao No. 13,No.33 were planted with five water treatments in an experimental field,their photosynthetically active radiation(PAR) of cotton canopy were recorded by a linear quantum sensor at the six key growth stages.Their absorbed photosynthetically active radiation(APAR) and fractional interception of absorbed photosynthetically active radiation(FAPAR) were calculated from PAR,meanwhile their diurnal change and variation of growth stages were analyzed.【Result】There were all parabolic curve in the change of APAR of two cotton cultivars under five water treatments at the six growth stages,their minimum APAR values both occurred at 08:00 am and 20:00 pm,their maximum APAR values occurred at 14:00 and 12:00 respectively.The diurnal change of FAPAR were both-shaped curve,their minimum peak values of FAPAR both occurred at 14:00,two maximum peaks of FAPAR both occurred at forenoon and afternoon.APAR and FAPAR of two cotton cultivars reached the lower values at the initial flowering stage,the minimum values at later full boll stage,their maximum values occurred at full flowering stage,flowering and boll-forming stage,respectively,the variation of APAR and FAPAR during the growth phase were in accordance with development progress of cotton.FAPAR sequences of two cotton cultivars under five water treatments were all W_5 W_4 W_3 W_2 W,at each growth period.【Conclusion】Cotton with different water status affected their variation of APAR and FAPAR,the diurnal change of APAR,FAPAR and the variational characteristics of cotton APAR and FAPAR at the growth stage can be used to monitor growth status of cotton canopy.