Abstract:

Taking alfalfa(Medicago Sativa L. victorian)as materials, a hydroponic experiment was conducted to study the influence of osmotic stress on stomatal movement, transpiration rate, photosynthesis and growth of alfalfa seedlings using 15% of PEG-6000 (TM) simulated water stress. The results showed that compared to CK, TM cultured alfalfa seedlings stomatal density, length, width, the width of Stomatal aperture were reduced by 55%, 46.9%, 12% and 56%(P<0.05), respectively; transpiration rate, water use efficiency and the photosynthetic light utilization were reduced by 37%, 30%, 33.3%(P<0.05), respectively; the plant height, root length, root number of Alfalfa decreased by 22.3%, 4.0% and 34.9% (P<0.05), respectively. Correlation analysis showed that plant height had very significant positive correlation with Pn (r=0.830), and a significant negative correlation with Gs (r=-0.720); Tr had very significant negative correlation with root, plant height, and number of fibrous roots (r=-0.910 r =-0.980, and r=-0.890, respectively). In summary, osmotic stress affected the changes of Alfalfa Stomatal aperture and density and then influenced transpiration, which led to the change of alfalfa root length and root number, the reduction of the use efficiency of the body effective water and the change of the Photosynthetic capacity. It might be one of the main factors to reduce the alfalfa yield.

Key words: Alfalfa, Osmotic stress, Stomatal movement, Transpiration rate, Photosynthetic characteristics

摘要：

以紫花苜蓿品种维多利亚（Medicago Sativa L.'victorian'）为材料，15% PEG-6000（TM）模拟渗透胁迫，水培法研究渗透胁迫对幼苗气孔、光合蒸腾及生长的影响。结果表明：胁迫第7天时CK与TM相比，苜蓿幼苗气孔密度、长度、宽度和气孔开度宽分别减少了55%，46.9%，12%和56%（P<0.05）；蒸腾速率（Tr）、水分利用效率（WUE）和光能利用率（LUE）分别降低了37%，30%和33.3%（P<0.05）；苜蓿地上部分株高和地下部分根长、侧根数分别下降了22.3%，4.0%和34.9%（P<0.05）。苜蓿的株高与净光合速率（Pn）呈极显著正相关（r=0.830），与气孔导度（Gs）呈显著负相关（r=-0.720），蒸腾速率（Tr）与根长、株高、侧根数呈极显著负相关，（r=-0.910，r=-0.980，r=-0.890）。综上，渗透胁迫影响了气孔开度和密度造成蒸腾变化，体内有效水分利用率降低而改变光合能力，苜蓿生物量出现显著下降，这可能是渗透胁迫下苜蓿产量降低的主要因素之一。

关键词: 紫花苜蓿, 渗透胁迫, 气孔运动, 蒸腾速率, 光合作用