Study On The Irrigation Index During Berry Developmental Periods Of Grapevine

So far,researches on precision irrigation of fruit trees have mainly focused on the selection of plant water status indicators and the impacts of different irrigation treatments on the production of fruit trees.While the researches upon determining the irrigation index and its application threshold based on the real-time response of different plant organs to soil water potential during various phenological periods have not been reported.In this paper,eight-year potted 'Kyoho' grapevines were used as experimental materials,and the relationships between rooting-zone soil water potential with shoots diameter,berry growth and leaf net photosynthetic rate were explored through the photogrammetry,real-time monitoring of soil water potential and continuous determination of diurnal change of leaf photosynthetic traits during berry first rapid growth period and veraison.The results showed that:1.During berry first rapid growth period and veraison,MDS increased significantly when the soil water potential was-8.89 kPa and-9.21 kPa,respectively.There are highly significant differences and negative growth in MXDG and MNDG when the ?soil was below-17.34 kPa and-16.46 kPa,separately.MDS,MXDG and MNDG of shoots can reflect the decline of soil water potential in stages without showing successional variation.2.With the decline of soil water potential,berry growth presented four phases below:high speed growth,rapid growth,slow growth and shrinking phase.During berry first rapid growth period,the berry expansion rate ranges of these four stages were 0.10?0.31mm2·h-1,0.03?0.10 mm2·h-1,0.00?0.03 mm2·h-1 and<0.00 mm2·h-1.Meanwhile,the berry expansion rate ranges of these four stages at veraison were 0.11?0.26 mm2·h-1,0.02?0.11 mm2·h-1,0.00?0.02 mm2·h-1 and<0.00 mm2·h-1,which can reflect the successional variation of soil water potential.3.The periodic changes of Pn were not affected remarkably with the decline of rooting-zone soil water potential.However,the daily maximum of Pn denonstrated a downtrend.The daily maximum of Pn was not affected sharply as rooting-zone soil water potential was maintained in the range of 0?27.3kPa during berry first rapid growth period.While it decreased significantly when soil water potential decreased to-36.8 kPa at veraison.The suitable irrigation index for eight-year 'Kyoho' grapevine was determined by considering the expansion growth of berries,the accumulation of photosynthetic products,the control of excessive growth of shoots,and no negative effect on the leaf Pn as a whole.The suitable irrigation index during berry first rapid growth periods and veraison is berry expanding rate,whose corresponding application thresholds are 0.061?0.084 mm2h-1 and 0.025?0.077 mm2h-1.