RAPID AND REVERSIBLE MODIFICATIONS OF EXTENSION CAPACITY OF CELL-WALLS IN ELONGATING MAIZE LEAF TISSUES RESPONDING TO ROOT ADDITION AND REMOVAL OF NACL
Pm. Neumann, RAPID AND REVERSIBLE MODIFICATIONS OF EXTENSION CAPACITY OF CELL-WALLS IN ELONGATING MAIZE LEAF TISSUES RESPONDING TO ROOT ADDITION AND REMOVAL OF NACL, Plant, cell and environment, 16(9), 1993, pp. 1107-1114
A creep extensiometer technique was used to provide direct evidence th
at short (20 min) and long-term (3 d) exposures of roots to growth inh
ibitory levels of salinity (100 mol m(-3) NaCl) induce reductions in t
he irreversible extension capacity of cell walls in the leaf elongatio
n zone of intact maize seedlings (Zea mays L.). The long-term inhibiti
on of cell wall extension capacity was reversed within 20 min of salt
withdrawal from the root medium. Inhibited elongation of leaf epiderma
l tissues was also reversed after salt removal. The salt-induced chang
es in wall extension capacity were detected using in vivo and in vitro
assays (shortly after localized freeze/thaw treatment of the basal el
ongation zone). The rapid reversal of the inhibition of wall extensibi
lity and leaf growth after salt removal from root medium of long-term
salinized plants, suggested that neither deficiencies in growth essent
ial mineral nutrients nor toxic effects of NaCl on plasmamembrane viab
ility were directly involved in the inhibition of leaf growth. There w
as consistent agreement between the scale, direction and timing of sal
inity-induced changes in leaf elongation growth and wall extension cap
acity. Rapid metabolically regulated changes in the physical propertie
s of growing cell walls, caused by osmotic (or other) effects, appear
to be a factor regulating maize leaf growth responses to root saliniza
tion.