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 5 super(th) 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