Salt excretion through the cuticle without disintegration of fine structures in the salt glands of Rhodes grass (Chloris gayana Kunth)

Some salt-tolerant plants belonging to the Poaceae possess bicellular salt glands that excrete salt-containing water. To clarify the excretion process from the outer cell of the bicellular salt gland (cap cell), unwashed and washed fresh leaves of Rhodes grass (Chloris gayana Kunth), Poaceae, were cryo-fixed rapidly, and the surface fine structures of the leaves were observed by cryo-scanning electron microscopy with high resolution. The cuticle on the cap cell did not have any pores or signs of rupturing. The cuticle of the cap cells lacks the epicuticular waxes that cover most surfaces of leaf epidermis. After excreted droplets on the salt glands were completely removed by washing with water, re-excreted droplets were observed 3 h later. These findings indicate that the bicellular salt glands of Rhodes grass excrete salt-containing water continuously through the wax-free cuticle of the cap cell without disintegration of the cuticular structure.