1994 Volume 63 Issue 3 Pages 611-618
To clarify the involvement of RNA metabolism in chill-tolerant figleaf gourd (Cucurbita ficifolia Bouch) and chill-intolerant cucumber (Cucumis sativus L), the effects of root temperatures ranging from 12 ° to 26 °C on root RNA concentrations and root growth were studied. RNA concentrations in figleaf gourd roots were affected by root temperature, being lowest at 23 ° to 26 °C, increasing with lower temperatures and peaking at 14 °C; concentrations then decreased at 12 °C. The concentration at 14 °C was 2.5 times higher than it was at 23 ° to 26 °C. A similar trend was observed in cucumber roots, but much less dramatic. The marked increase of RNA concentration in figleaf gourd roots was due to increases of such RNA species as rRNA, mRNA, tRNA, and RNA precursors. The extent of increases was most prominent in tRNA. Six days after exposure to 14 °C, the roots were transferred to 23 °C. The move caused a rapid drop of RNA concentration within 2 days to a pre-chill level in figleaf gourd roots but no change in cucumber roots. The marked increase of RNA concentration in figleaf gourd roots exposed to 14 °C may be caused by the low temperature-induced net accumulation of RNAs. Root growth of figleaf gourd paralleled that of RNA concentration/temperature curve; that of cucumber was nearly linear from 12 °C to 26 °C. The marked increase in RNA concentration in figleaf gourd roots exposed to 14 °C is discussed in relation to chilling tolerance.