Cuticle and Cell Wall Thickness: Relation to Mechanical Strength of Whole Leaves and Isolated Cells from Some Forage Legumes1

Abstract

Leaflets from seven legumes were examined by electron microscopy to determine the thickness of the cuticle, outer tangential epidermal cell wall, and mesophyll cell wall. Sainfoin (Onobrychis viciifolia Scop.), cicer milkvetch (Astragalus cicer L.), and birdsfoot trefoil (Lotus corniculatus L.) have a high resistance to leaf and cell rupture while alfalfa (Medicago sativa L.), arrowleaf clover (Trifolium vesiculosum Savi), red clover (T. pratense), and white clover (T. repens L.) are more susceptible. The cuticle and the epidermal cell wall and the mesophyll cell wall were thicker in sainfoin, cicer milkvetch, and birdsfoot trefoil. Correlation coefficients show a strong relationship between a thick cuticle, epidermal, or mesophyll cell wall and a greater resistance to certain types of mechanical damage in whole leaflets or isolated cells. Among the species, cuticle thickness measurements provided a larger coefficient of variation than thickness measurements for epidermal cell wall plus cuticle or cell wall alone. Those legumes which had thicker cuticles and cell walls are considered bloat‐safe. Epidermal cell wall and cuticle and mesophyll cell wall thickness are probably leaf morphological characters which contribute to the non‐bloating nature of some forage legumes.