EFFECT OF EXTREME TEMPERATURE-CHANGES ON GROWTH AND DRY-MATTER PRODUCTION OF YOUNG TOMATO PLANTS

With young tomato plants the effect of distinct short-term temperature changes on dry matter production and CO2-gas-exchange was tested. Photosynthetic rates were highest at 22-degrees-C. Below 10-degrees-C growth was drastically reduced. High root temperature could not compensate for low air temperature. When conditions had changed plant adaptation occurred with some delay. Negative effects of low temperature acted more severe with young plants showing distinctly reduced net assimilation rates and reduced leaf growth. The older the plants the less changes especially of leaf growth were found. Plant growth and uptake of P were correlated. Having a favourite temperature regime the leaves showed a P content of ca. 0,9% (dry matter). With low temperature after 5-6 weeks this was reduced to 0,4%.