Can cell wall peroxidase activity explain the leaf growth response ofLolium temulentumL. during drought?

In two experiments, the effect has been investigated of a mild and a more prolonged drought on the spatial distribution of growth, epidermal cell lengths and cell wall peroxidase activities in the leaf elongation zone of the grass species Lolium temulentum L. In both experiments drought reduced the size of the elongation zone and local rates of elongation within it. Abrupt increases in cell wall-associated peroxidase activity occurred at or close to the position where elongation ceased in the leaf elongation zones of well-watered and mildly drought-stressed plants. More prolonged drought caused a 200–300% increase in the cell wallassociated peroxidase activity in the elongation zone only. The significant increase in the elongation zone cell wall peroxidase activity and its spatial variation provides evidence of a potentially causal role for cell wall-associated peroxidase in restricting cell expansion during drought.