Study Of Microscopic Structure Of Dehydration Resistance In Two Duckweeds

Differences in anatomical structure of the fronds in two Duckweeds, Lemna minor and Spirodela polyrrihiza (L.) Schleid which cultured in Hoagland Medium was investigated by freehand sectioning; The survival rate, variation of morphological characteristics and microscopic structures was studied using traditional methods of plant physiology and improved paraffin sectioing, and PEG6000-Hoagland solution of different concertrations was used as culture medium for simulating natural soil dehydration conditions in the process. Triticum aestivum (Linn.), which is one of mesophytes was choosen as a control to compare and evaluate the dehydration-resistance ability of two species of Lemnacea in different level of soil dehydration conditions by artificial control.The result showed that:(1)The fronds part anatomical structure of two species is similar to those typical structures of aquatic plants, but there were some obvious differences between these two Duckweeds. The fronds thickness of Spirodela polyrrihiza (L.) was significantly greater than that of Lemna minor; Ventilation structure in mesophyll is more developed; There were a lot of calcium oxalate crystals and raphides in cells constituting each part of the Spirodela polyrrihiza (L.) fronds, but only raphides in Lemna minor fronds; Epidermis cells of two Duckweeds fronds varies in shapes and size, stomatal density and area of Spirodela polyrrihiza (L.) fronds was smaller and guard cell contains more chloroplast than that of Lemna minor;(2) PEG dehydration stress treatments causes a certain degree of harm for morphology in fronds of two Duckweed, the extent of damage increased as srtess intensity aggravating, and thickness of two Duckweeds fronds decreased rapidly and continuously.(3) Different dehydration conditions would affect the structure of both mesophyll cells and chloroplast of two Duckweeds and Triticum aestivum (Linn.) seedlings seriously:morphological structure of the mesophyll cells and chloroplast is normal and complete before dehydration stress treatment; After dehydration, the mesophyll cells were deformed and chloroplast became inflated and arranged chaotically within mesophyll cells.Above all, Duckweed showed stronger resistance under serious dehydration conditions than Triticum aestivum (Linn.), and Lemna minor is more sensitive to changes of water conditions of environment, in other words, Spirodela polyrrihiza(L.)has stronger tolerance and adaptability to dehydration stress.