海滨沙地砂引草对沙埋的生长和生理适应对策

在2009和2010年春夏季通过对烟台海滨沙地自然生长的耐沙埋植物砂引草(Messerschmidia sibirica Linn)进行不同厚度(1/3株高-轻度沙埋、2/3株高-中度沙埋、3/3株高-重度沙埋)沙埋试验,并测定沙埋过程中土壤温度、土壤含水量、叶片鲜重(FW)、干重(DW)、植株相对高度(%)、叶片细胞膜透性、相对含水量、(丙二醛)MDA、抗氧化酶活力(过氧化物岐化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))、脯氨酸、可溶性糖含量的变化以探讨砂引草抗沙埋的生长和生理调节策略,为未来砂引草的科学管理和应用提供理论指导。结果表明,在沙埋第5天、第10天,随着沙埋厚度的增加土壤温度下降,土壤含水量增加,植株相对高度和整株砂引草叶片FW和DW呈上升趋势,同一植株沙上叶片FW、DW不断增加,沙下叶片FW、DW则不断减少。在沙埋第5天,不同厚度沙埋处理的植株叶片细胞膜透性和MDA含量均较对照低,而整株植物叶片SOD、CAT活力和脯氨酸含量均较对照高。同一植株沙下叶片细胞膜透性、MDA、脯氨酸含量及SOD和CAT活力均低于沙上叶片。研究表明,轻度和中度沙埋使沙上叶片受到地面热辐射、干旱、高温胁迫影响,导致叶片内含水量下降,膜脂过氧化加强,膜受损。但同时叶片中快速激活的保护酶和积累的脯氨酸抑制膜脂过氧化可能是保护沙埋后沙上叶片能快速生长的重要生理调控机理。在重度全埋枝叶处于沙下时,沙下缺氧和黑暗抑制了叶片呼吸作用和光合作用,同时缺氧也抑制了叶片对营养物质的消耗使叶片成为茎尖生长的物质和能量供体,促使暗中茎顶端不断的延伸生长冲出沙土再生。砂引草耐全埋的再生能力进一步表明,砂引草在海岸沙丘固沙、保滩、护岸和植被恢复上将具有重要开发和应用前景。

Growth and physiological adaptation of Messerschmidia sibirica to sand burial on coastal sandy

Messerschmidia sibirica Linn, Siberian sea rosemary, may be useful in the restoration and protection of sand dunes. We explored its ability to withstand varying levels of sand burial in the Yan Tai coastal dune in the spring and summer of 2009 and 2010. Four levels of sand burial treatments were set up: no-sand burial (control), light sand burial (1/3 of plant height), moderate sand burial (2/3 of plant height) and severe sand burial (plant fully covered by sand). Changes in soil temperature, soil moisture, fresh weight (FW), dry weight (DW), relative plant height, plasma membrane permeability, MDA content, osmotic regulation, and activity of antioxidant enzymes in the leaves of plants in different levels of sand burial were investigated to elucidate the strategies used to maintain physiological and biochemical processes during growth in the different environments. Soil temperatures below sand decreased while soil water content increased with increasing levels of sand burial. Plants in light and moderate sand burials were taller than controls. In individual plants, the FW and DW of leaves above sand increased while FW and DW of leaves below sand decreased. On the 5th day after sand burial, the leaves of whole plants in each of the three levels of sand burial had lower membrane permeability, MDA and proline contents and higher levels of activities of SOD and CAT than controls. Also, in individual plants, membrane permeability, MDA and proline contents, and activities of SOD and CAT in the leaves below sand were lower than in leaves above sand. The decrease in these physiological indicators was therefore correlated with increases in soil moisture and lower soil temperatures. Leaves above sand appeared to suffer from stronger ground thermal radiation, drought stress, and high temperature. These findings suggest that under light and moderate sand burial, antioxidant enzymes and proline play an important physiological regulating role in retarding lipid peroxidation and protect the leaves above sand, allowing them to grow rapidly and helping the plant avoid further sand burial. Moreover, under severe sand burial, although darkness and low oxygen limit photosynthesis and respiration of the buried leaves, those leaves can keep more nutrients to transfer to the apex of the shoot to make it grow and emerge above sand. Our results confirm that Messerschmidia sibirica Linn has a high resistance to even severe sand burial and uncovers some of the physiological strategies employed in this resistance. Thus it may be a very suitable plant for vegetation restoration, sand fixation, and protecting beaches in coastal dunes.