Leaf cuticle and water loss in maize lines differing in dehydration avoidance

The plant cuticle plays an important role in protecting plants against water loss. The objectives of this study were to investigate the relationships between (a) epidermal water loss and epidermal cell-wall thickness and cuticle thickness, and (b) epidermal water loss and cuticular wax quantity and composition in two lines of Zea mays L. (maize) differing in dehydration avoidance. Epidermal water loss from 16-day-old plants was determined by measuring water loss in shoots and detached leaves (leaf blades) under dark conditions. The results revealed an inverse relationship between the epidermal water loss and cell-wall and cuticle thickness. A maize line with lower rates of shoot and detached-leaf water loss, ZPBL 1304, had thicker epidermal cell wall and thicker cuticle than a maize line with higher rates of shoot and detached-leaf water loss, ZPL 389. The amount of cuticular wax did not correlate inversely with epidermal water loss, suggesting that wax quantity alone may not be important in epidermal transpiration. Water flow through the cuticle may thus be more complex than simple diffusion through a homogenous lipid layer.