Fusicoccin counteracts inhibitory effects of high temperature on auxin-induced growth and proton extrusion in maize coleoptile segments.

Plant growth and development are tightly regulated by both plant growth substances and environmental factors such as temperature. Taking into account the above, it was reasonable to point out that indole-3-acetic acid (IAA), the most abundant type of auxin in plants, could be involved in temperature- dependent growth of plant cells. We have recently shown that growth of maize coleoptile segments in the presence of auxin (IAA) and fusicoccin (FC) shows the maximum value in the range 30-35 degrees C and 35-40 degrees C, respectively. Furthermore, simultaneous measurements of growth and external medium pH indicated that FC at stressful temperatures was not only much more active in the stimulation of growth, but was also more effective in acidifying the external medium than IAA. The aim of this addendum is to determine interrelations between the action of IAA and FC (applied together with IAA) on growth and medium pH of maize coleoptile segments incubated at high temperature (40 degrees C), which was optimal for FC but not for IAA.