| The growth development and water consumption and droughtresistance of four evergreen tree species ( Ligustrum lucidum , Pinustabulaeformis , Ligustrum sinense , Platycladus orientalis)were studied bypotted-plant in Yangling China. Two water treatments were set by artificiallycontrolling soil moisture. One was normal water supply (70%θf), and the otherwas severe water deficit (30%θf). The results showed that different watersupplies significantly affected the survival ratio, lengthening growth rate, leafcharacteristic, branching pattern, biomass and their distribution of the four treespecies. On severe water deficit condition, the survival ratio decreased notably,especially Pinus tabulaeformis. The growth of leaves area and length ofneedle-leaves was obviously hampered on drought stress. The commoncharacteristic of four species about biomass was reduced than normal soil watercontent. The leaf biomass dry weight decreased, in contrast to the root biomassdry weight increased, especially the two broad-leaves tree species. The situationof branch of two broad-leaves evergreen tree species was greatly worse. Both totalbranch number and total branch length were decreased. And their bifurcation ratiowas decreased too. Very important to photosynthesis, outer branches numbernotably descended and length become short. Different soil water content hadaffected water consumption character of four evergreen tree species. Themaximum amount of daily and monthly water consumption both emerged ingrowth season. The maximum consumption amount time was ahead of that ofnormal soil water content one month. The other hand, the minimum amountemerged in winter from December to February the next year. The daily amount ofwater consumption on normal water content was easier to fluctuate according tothe weather condition than that on sever drought stress. The fluctuant range ofwater consumption on stress condition was smaller than that on normal soilmoisture. Because of sever drought stress, the water consumption amount of dayand night ratio decreased. And the ratio of day and night in summer was lowerthan that of in spring and autumn. There were greatly changes of mechanism ofleaves water physiology and biochemistry due to severe soil water deficit. Thechanges had period or season regular character. With the season turning, thecapacity of resistance hard environment was different, strengthening or weakening.From whole view, this capacity of two needle-leaves tree species was better thanthat of two broad-leaves tree species. The ability of resistance drought stress haddifference between two broad-leaves tree species. This ability of Ligustrumsinense was lower than Ligustrum lucidum, but this situation was reversed inwinter. This phenomenon illuminated the ability of resistance chilling or freezingthe former was better than that of the latter. Different soil water content hadobviously affected on osmotic adjustment substance and photosynthetic pigmentcontent of four evergreen tree species. The range and sensitive of osmoticadjustment capacity of the needle-leaves evergreen tree species were better thanthose of osmotic adjustment capacity of the broad-leaves evergreen tree species.But the absolute content of proline and soluble sugar of the needle-leavesevergreen tree species was lower than that of the broad-leaves evergreen treespecies. The content of K+ had no obvious difference among four evergreen treespecies. The soluble sugar was the effective osmotic adjustment substance used toresist the hard environment stress on the four evergreen tree species respectively.Different soil moisture had obviously affected on protective enzyme systemactivities. At the beginning, the activities increased, but a little time later,decreased and kept stable. Their activities had season variation irregular on fourevergreen tree species. Contrasted the content of photosynthetic pigment andosmotic adjustment substance and hormone ABA and the activities of prote...
|
PDF Full Text Request