沙埋对沙米幼苗生长、存活及光合蒸腾特性的影响

沙米(Agriophyllum squarrosum)是藜科沙蓬属1年生沙生植物,广泛分布于我国各主要沙漠和沙地中。为了解沙埋对沙米生长、存活和光合蒸腾特性影响,2010-2011年在科尔沁沙地研究了不同沙埋深度下沙米幼苗高度、存活率、光合速率、蒸腾速率、气孔导度和水分利用效率的变化,结果表明:沙米具有极强的耐沙埋能力。埋深为株高25%时,沙米幼苗存活率和株高显著增加,埋深为株高50%-100%时,其株高和存活率虽有下降,但与非沙埋对照差异不显著。当沙埋深度超过株高后,其株高和存活率急剧下降,但沙埋达到株高266%时仍然有部分幼苗存活。沙埋第5天,随着沙埋深度的增加,沙米幼苗的光合速率缓慢下降,蒸腾速率、气孔导度和水分利用效率均呈波动式变化。随着沙埋时间的延长,和对照相比,沙米幼苗的光合速率、蒸腾速率和气孔导度均随沙埋深度增加而大幅度下降,但水分利用效率仍呈波动式变化。沙埋第15天时其光合速率、蒸腾速率、气孔导度和水分利用效率分别较非沙埋对照下降了86.7%、89.0%、90.0%和4.2%。相关分析表明,沙米幼苗的存活率和高生长与其光合速率、蒸腾速率、气孔导度变化呈显著正相关,而其光合速率、蒸腾速率、气孔导度之间也呈显著正相关,但与水分利用效率的相关性未达到显著水平。沙埋胁迫下沙米幼苗存活率下降和生长抑制不仅源于沙埋造成幼苗顶土困难和光合面积减少,光合速率、蒸腾速率和气孔导度下降也是重要原因。

Effects of sand burial on growth, survival,photosynthetic and transpiration properties of Agriophyllum squarrosum seedlings

Agriophyllum squarrosum is an annual psammophyte species and wildly distributed in all deserts and sand lands in China. Changes of plant height, survival rate, photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and water use efficiency (WUE) of A. squarrosum seedlings was measured in a sand burial experiment during 2010-2011 in Horqin Sand Land of Inner Mongolia to understand effect of sand burial on the growth, photosynthesis and transpiration of annual psammophyte seedlings. The experiment included ten burial treatments: buried to 0% (CK, no burial), 25% (A), 50% (B), 75% (C), 100% (D), 133% (E), 166% (F), 200% (G), 233% (H) and 266%(I) of seedling height. The results showed that A. squarrosum had a strong ability to withstand sand burial. The survival rate and the plant height of A. squarrosum seedlings increased significantly at 25% burial depth of the seedling height. When subjected to sand burial at 50%-100%, the difference was not significant between the sand-buried treatments and the none-sand buried CK although the plant height and the survival rate decreased. The survival rate and the plant height decreased significantly only when the burial depth exceeded the height of the seedlings, but some individuals still kept survived when the burial depth was 266% of the seedling height. Buried by sand to the fifth day, the photosynthesis rate of A. squarrosum seedlings decreased slowly, the transpiration rate and the stomatal conductance and the water use efficiency fluctuated greatly with the increase of sand burial depth. The photosynthesis rate and the water use efficiency decreased by 14.6% and 19.2%, and the transpiration rate, the stomatal conductance increased by 3.0% and 3.7% in the I treatment than that in the CK, respectively. With the prolongation of sand burial time, the photosynthesis rate, the transpiration rate and the stomatal conductance decreased significantly, but the water use efficiency was still fluctuated with increase of sand burial depth. Buried in sand to the tenth day, the photosynthesis rate, the transpiration rate, the stomatal conductance and the water use efficiency decreased by 89.7%, 84.4%, 85.7% and 54.0% in the I treatment than that in the CK, respectively. Buried in sand to the fifteenth day, the photosynthesis rate, the transpiration rate, the stomatal conductance and the water use efficiency decreased by 86.7%, 90.0%, 89.0% and 4.2% in the I treatment than that in the CK, respectively. Correlation analysis suggested that the survival rate and the seedling height had significant and positive correlations with the photosynthesis rate, the transpiration rate, the stomatal conductance and the water use efficiency. There were significant positive correlations among the photosynthesis rate, the transpiration rate and the stomatal conductance, but the correlation was not significant between them and the water use efficiency. It was concluded that sustained severe burial by sand had a significant damage to survival and growth of A. squarrosum seedlings. The decrease of the survival rate and the plant height in A. squarrosum seedlings were resulted not only from emergence difficult and decrease of photosynthetic area under sand burial stress, but also from decrease of the photosynthetic rate, the transpiration rate and the stomatal conductance.