PROPERTIES OF PLASMA-MEMBRANES OF PHSP 70-IPT TRANSFORMED TOBACCO (NICOTIANA-TABACUM)

Application of 10 successive daily heat shocks reduced the growth of c ontrol tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) plants by a bout 15%; for Phsp 70-ipt transformed plants this is about 48%. The sh oot diameter of these ipt-transformed plants increased by about 75%. I n addition, in heat shock treated ipt-plants (IPT-HS) the upper latera l buds grew out due to a reduction of apical dominance. The older leav es of IPT-HS plants had a higher chlorophyll content. In spite of the observed effects due to a higher endogenous cytokinin content in the I PT-HS plants, no significant changes were observed on the plasma membr ane fatty acid composition, nor on its fluidity as determined from the steady-state fluorescence anisotropy of DPH. Only a minor change in t he plasma membrane free sterol composition was found as evidenced by a 20% decrease in the stigmasterol to sitosterol ratio in IPT-HS, indic ative for a possible anti-senescence effect of enhanced endogenous cyt okinins, but without significant effects on the plasma membrane functi on. (C) 1997 Elsevier Science Ltd. All rights reserved.