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Caraganaspecies are commonly distributed in desert regions. We hypothesized that the photosynthetic traits of desertCaraganaspecies could acclimated well to the desert environments, which are characterized by high temperature, intense radiation, and low moisture. To test our hypothesis, we studied the responses of photosynthesis to light, temperature and humidity, and fluorescence parameters of fourCaraganaspecies from desert region and oneCaraganaspecies from steppe region in Inner Mongolian Plateau. The desertCaraganaspecies had higher light compensation point, light saturation point, optimum temperature for photosynthesis, and lower optimum relative air humidity for photosynthesis than the steppeCaraganaspecies, and their net photosynthesis rates (Pn) were higher under high temperature, intense sunlight, and low humidity. The nonphotochemical quenching efficiency(NPQ)and minimal fluorescence(Fo)of the desertCaraganaspecies were higher, and the values of maximum fluorescence(Fm), maximum quantum yield(Fv/Fm), relative quantum yield (ΦPSII), and photochemical quenching coefficient (qP) were lower, except forC. korshinskii. The electron transport rate (ETR) of the desertCaraganaspecies was greater or similar to that ofC. microphylla.In summary, the photosynthetic traits of the desertCaraganaspecies acclimated well to desert environment, although such acclimation might be still not sufficient. The order of photosynthetic acclimation of the four species to desert environment is:C. korshinskii > C. stenophylla > C. tibetica > C. roborovskyi. [ABSTRACT FROM AUTHOR]

With six Pinus sylvestris var. mongolica plantations (Huinan, Xifeng, Fujia, Zhanggutai, Naiman and Wulanaodu) along an aridity gradient in the Horqin sandy land, we examined the changes in non-structural carbohydrates (NSCs) and nitrogen (N) contents of current and one-year-old needles and twigs, to explore the carbon supply and demand status as well as the nutrient accumulation strategies of P. sylvestris var. mongolica under drought. The results showed that the contents of NSCs and soluble sugars in needles and twigs of P. sylvestris var. mongolica plantations significantly decreased with increasing aridity. From the most humid site (Huinan) to the most aridity site (Wulanaodu), the soluble sugar contents in current and one-year old needles of P. sylvestris var. mongolica decreased from 12.8% and 12.5% to 9.0% and 9.5%, respectively. The soluble sugar contents in current-year old twigs decreased from 15.6% to 9.2%. With increasing aridity, the starch contents in needles and twigs remained relatively stable, soluble sugars/starch ratio in current and one-year old needles decreased, the N contents in current and one-year old twigs significantly increased. The P. sylvestris var. mongolica plantations in the Horqin sandy land consumed soluble sugar storage under drought, resulting in a risk of mortality from 'carbon starvation'. P. sylvestris var. mongolica tended to maintain stable starch storage and accumulate N in twigs to cope with long-term drought stress.

With pot experiment, this paper studied the effects of silicon supply on drought-resistance capability of maize plant. The results showed that under mild and severe drought stress, supplying silicon could increase the plant biomass by 31.1%-33.3% and 23.7%-40.5%, respectively, compared with the control. Silicon enhanced the net photosynthetic rate by 10.9% --28.8%, increased the chlorophyll content and POD, SOD and CAT activities by 4.0% -11.9%, 6.4% -26.4%, 17.8% -26.8% and 3.2%-33.5%, respectively, and restrained the increase of leaf plasma membrane permeability and MDA content. Correlation analysis indicated that there was a significant correlation between plant dry matter accumulation and diurnal photosynthetic cumulates (r = 0. 9357, P < 0.05), demonstrating that the enhancement of photosynthesis under effect of silicon supply was the main factor inducing the increase of dry matter accumulation under drought stress. The higher antioxidative enzyme activities with silicon supply lightened the injury effect of free radicals, being another important factor inducing the increase of plant drought-resistance capability.