| Chilopsis linearis that was introduced from west of USA is a kind of desert shrub. The ecophysiological responses of Potted 2-year-old Chilopsis linearis seedlings to different soil water stress were studied when grown under three different soil moistures of 80%~90%(light degree soil water stress (LWS)), 50%~60%(middle degree soil water stress (MWS)) and 20%~30%(heavy degree soil water stress (HWS)) of field water-holding capacity. The results are as follows:1. Soil water stress made water potential (?s), free water content (Va) and relative water content of C. linearis leaves decreased, bound water content (Vs), water saturation deficiency (WSD) and ratio of bound water content to free water content (Vs/Va) increase, leaf water-holding abilities weaken, transpiration rate (Tr) enhance. But tissue total water content kept steady on the whole under soil water stress. The response sensitivities of these indexes to soil water stress were different. MWS didn't make RWC, WSD and water-holding abilities change obviously in compare with LWS, but HWS made them change clearly. Based on the LWS in august, both MWS and HWS made ?S, VS, Va, VS/Va and Tr change obviously, ?S, Va and RWC decreased by 48.81%, 52.4% and 6.29% respectively, while Vs, WSD, VS/Va and Tr increased by 100.9%, 109.98%, 145.5% and 62.18 respectively. With seasonal changes of climate, ?S, VS, Va, Tr showed obviously monthly courses under different soil water stress conditions.2. Soil water stress made net photosynthetic rate (Pn), water use efficiency (WUE) and light compensation point (LCP) of C. linearis decrease, dark respiration rate (DRR) weaken. Under LWS, MWS and HWS conditions, diurnal mean values of Pn are 8.19 # molm-2s-1, 7.98 # molm-2s-1 and 0.86 # molm-2s-1 respectively in July, 9.42 # molm-2s-1, 8.38 # molm-2s-1 and 5.65 # molm-2s-1 in August, and 4.74 # molm-2s-1, 3.19 # molm-2s-1 and 2.73 # molm-2s-1 in September. In July, August and September, LCP are respectively 321.7 # molm-2s-1, 180.6 # molm-2s-1 and 373.5 # molm-2s-1, and DRR are respectively 5.08 # molm-2s-1, 3.28 # molm-2s-1 and 7.53 # molm-2s-1. Pn showed remarkably diurnal and monthly courses along with variations of environmental factors. The diurnal courses of Pn under LWS and MWS conditions are double-peak type "flag curves" with clear photosynthesis midday depression phenomena in July. But it is the single-peak type "flag curve" under HWS condition. In August and September, all the diurnal courses of Pn of three treatments are double-peak type "flag curves". In July, August and September, the values of WUE under HWS condition decreased by 86.2%, 54.6% and 54.9% respectively on the base of WUE values under LWS condition. The values of LCP and DRR under HWS condition decreased by 51.65% and 56.4% respectively on the base of corresponding values under LWS condition.3. Soil water stress restrained C.linearis growth and development, reduced its biomass,made rate leaf area (RLA) and ratio of root to stem increase, leaf area decrease, taproot elongate, and made leaf number, ramification number and side-root number of individual decrease markedly. Compared with the dry biomass of C.linearis under LWS condition, leaves, stems, taproots and side-roots dry biomass under MWS condition decreased respectively by 61.05%, 36.93%, 45.15% and 18.48%, and did by 89.61%, 79.05%, 74.07% and 63.78% respectively under HWS condition. Total biomass of MWS and HWS declined by 40.89% and 77.08% respectively on the base of LWS, and ratio of root to stem augmented by 15.33% and 86%. The ratio of root to stem varied from 0.83 of LWS to 1.55 of HWS. The different declined extents of components biomass under different soil water stress conditions reflected its sensitivity of keeping balance between yield and survivorship.4. C.linearis showed a preferable whole-plant action on the ecophysiological responses to soil water stress. It depended chiefly on decreasing values of S, Pn, LCP and DRR, increasing ratio of Vs/Va, enhancing transpiration rate, and adjusting its biomass allocation to acclimatize itself t...
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