Properties of plasma membranes of Phsp 70-ipt transformed tobacco (Nicotiana tabacum).

Application of 10 successive daily heat shocks reduced the growth of control tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) plants by about 15%; for Phsp 70-ipt transformed plants this is about 48%. The shoot diameter of these ipt-transformed plants increased by about 75%. In addition, in heat shock treated ipt-plants (IPT-HS) the upper lateral buds grew out due to a reduction of apical dominance. The older leaves of IPT-HS plants had a higher chlorophyll content. In spite of the observed effects due to a higher endogenous cytokinin content in the IPT-HS plants, no significant changes were observed on the plasma membrane fatty acid composition, nor on its fluidity as determined from the steady-state fluorescence anisotropy of DPH. Only a minor change in the plasma membrane free sterol composition was found as evidenced by a 20% decrease in the stigmasterol to sitosterol ratio in IPT-HS, indicative for a possible anti-senescence effect of enhanced endogenous cytokinins, but without significant effects on the plasma membrane function.