Search

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.