Rapid and reversible modifications of extension capacity of cell walls in elongating maize leaf tissues responding to root addition and removal of NaCl

Abstract

ABSTRACTA creep extensiometer technique was used to provide direct evidence that short (20 min) and long‐term (3d) exposures of roots to growth inhibitory levels of salinity (100mol m‐3 NaCl) induce reductions in the irreversible extension capacity of cell walls in the leaf elongation zone of intact maize seedlings (Zea mays L.). The long‐term inhibition of cell wall extension capacity was reversed within 20 min of salt withdrawal from the root medium. Inhibited elongation of leaf epidermal tissues was also reversed after salt removal. The salt‐induced changes in wall extension capacity were detected using in vivo and in vitro assays (shortly after localized freeze/thaw treatment of the basal elongation zone). The rapid reversal of the inhibition of wall extensibility and leaf growth after salt removal from root medium of long‐term salinized plants, suggested that neither deficiencies in growth essential mineral nutrients nor toxic effects of NaCl on plasmamembrane viability were directly involved in the inhibition of leaf growth. There was consistent agreement between the scale, direction and timing of salinity‐induced changes in leaf elongation growth and wall extension capacity. Rapid metabolically regulated changes in the physical properties of growing cell walls, caused by osmotic (or other) effects, appear to be a factor regulating maize leaf growth responses to root salinization.