N. Snir et Pm. Neumann, MINERAL NUTRIENT SUPPLY, CELL-WALL ADJUSTMENT AND THE CONTROL OF LEAFGROWTH, Plant, cell and environment, 20(2), 1997, pp. 239-246
The possibility that changes in the plasticity of expanding cell walls
are involved in regulating early leaf growth responses to nutrient de
ficiencies in monocot plants was investigated. Intact maize seedlings
(Zea mays L.) which were hydroponically grown with their roots in low-
nutrient solution (1 mol m(-3) CaCl2) showed early inhibition of first
-leaf growth, as compared with seedlings on complete nutrient solution
. This early inhibition of leaf growth was not associated with reduced
cell production. However, segmental elongation along the cell expansi
on zone at the base of the leaf and the lengths of mature epidermal ce
lls were reduced by the low-nutrient treatment. Solute (osmotic) poten
tials in the expanding leaf tissues were unchanged. In contrast, low-n
utrient treatments significantly altered leaf plasticity, i.e. the irr
eversible extension caused by applying a small force in the direction
of leaf growth. For example, in vivo plasticity decreased, along with
leaf growth, after transfer of seedlings from complete nutrient soluti
on to low-nutrient solution for 15 h. Conversely, in vivo plasticity i
ncreased, along with leaf growth, after transfer of plants previously
grown on low-nutrient solution to complete nutrient solution for 15 h.
The nutrient treatments also induced similar changes in the in vitro
plasticity of the expanding leaf cell walls. There were no consistent
changes in elasticity. Thus, reductions in the plasticity of expanding
leaf cell walls appear to be involved in controlling the early inhibi
tion of maize leaf growth by root imposition of nutrient stress.