Abstract:

By analyzing different materials of Medicago sativa L. and Medicago falcata L.,this study aims to observe the leaf morphology and tissue anatomical structure of alfalfa under drought stress,and explore the adaptive changes in leaf morphology and anatomical structure of alfalfa seedlings under natural drought stress.This study used three alfalfa and two Medicago falcata L. as research materials,and set four different soil relative moisture contents(70%,55%,40%,and 25% of the maximum soil moisture capacity)for experiments. After 30 days of treatment,the morphological and anatomical structures of the leaves were determined. To investigate the response of alfalfa seedling leaves to natural drought stress by observing the leaf morphology and anatomical structure of purple and sickle alfalfa seedlings through electron microscopy. Drought stress would inhibit the growth of alfalfa leaves. With the increase of drought stress,the soil moisture decreased,the leaf length,leaf width,and leaf area of alfalfa and sickle alfalfa decreased,the thickness of upper epidermis increased,the thickness of leaf,mesophyll,and lower epidermis decreased,the thickness of palisade cell and sponge tissue decreased,the thickness of midrib center decreased,the palisade sea ratio gradually decreased,and the compactness of leaf tissue structure increased,the degree of looseness decreased and the degree of leaf vein protrusion increased. The intensity of drought stress was negatively correlated with leaf length,leaf width,leaf area,leaf thickness,mesophyll thickness,lower epidermis thickness,palisade cell thickness,sponge tissue thickness,midvein center thickness,palisade sea ratio,and leaf tissue structure porosity.It was positively correlated with the thickness of the upper epidermis,the tightness of leaf tissue structure,and the degree of leaf vein protrusion.

Key words: Alfalfa seedling leaves, Natural drought stress, Leaf morphology, Leaf dissection structure