| Popis: |
Pear jujube(Ziziphus jujuba Mill.) as a common tree crop in the Loess Plateau region ofChina,but its ecological and economic benefits have failed to be fully realized because of the shortage of water resources.Therefore,improving jujube yield and water use efficiency are key goals.Studies of the water deficit index and water consumption rules can help to design more optimal irrigation systems and improve water use efficiency.In 2010 and 2011,we studied the water consumption of 4-year-old jujube plants subjected to one of four soil water treatments during their flowering and fruit development periods.We analyzed the correlation of water consumption to variation in trunk diameter and established a regression model.Our goal was to determine how pear jujube stem diameter responded to water conditions during the flowering and fruit development periods to determine a suitable water deficit index to use in building irrigation systems.The flowering and fruit development periods of pear jujube are critical water demand periods.Because these two processes define the main period of reproductive growth,they determine the quantity,volume,weight,and yield of fruit.Stem diameter change indexes included daily mean trunk diameter(MTD),daily maximum trunk diameter(MXTD),maximum daily shrinkage in trunk diameter(MDS),and daily growth of stem diameter(DG).The results indicated that(1) the tree water use increased with an increase in soil water content.Regardless of the treatment differences in soil water conditions,the maximum daily water use all occurred during the week following irrigation,and water consumption during the fruit expansion stage was greater than in flowering and fruit set stages.(2) Two years of experimental data proved that the logistic function could precisely express the changes in MTD and MXTD in the critical water demand periods of jujube,so these two indexes were equivalent in terms of assessing jujube trunk diameter growth during the study period,even though the growth rate varied annually and among treatments.(3) Under the high-water treatment,the indices derived from the trunk diameter(MTD,MXTD,MDS,and DG) were not sensitive to water consumption,while in the low-water treatment,MDS had a highly significant correlation with daily water use compared with the other indexes,indicating its potential as an indicator of jujube water consumption under water deficit conditions.The regression model between water consumption and trunk diameter that we established can be used to analyze the sensitivity of stem diameter variation to water deficit and to detect the water consumption status of pear jujube trees. |
