Effect of drought stress at vegetative growth stage on allometric relationships, root and shoot important characteristics of late and early maturing potato cultivars (Solanumtu berosum L.) under controlled conditions

Drought is one of the most important factors that affect crop production in Iran. Potato is often assumed to be a drought sensitive crop and its exposure to even short periods of water stress from germination through tuber growth can cause significant reduction in tuber yield. In order to study the effect of drought stress at vegetative stage on root characteristics and allometric relationships between root and shoot of early and late maturing cultivars of potato، a split plot experiment was arranged in a randomized complete block design with three replications at the Research Greenhouse of Ferdowsi University of Mashhad in 2011. Experimental factors were two irrigation levels including drought stress and non- stressed as main plots and 20 potato cultivars in two groups of late and early ripening plants as sub plots. In stressed treatment، plants were exposed to stress based on 60% of potato water requirement to reach field capacity. Non-stressed plants were full watered based on 100% water requirements. Studied traits were root depth، root dry weight، total roots length، root area، root diameter، root to shoot weight ratio، root to leaf weight ratio and root to leaf area ratio. Results showed that all traits were affected by drought stress treatments. The responses of different cultivars in the early and late maturing groups were different to the above characteristics. Drought stress increased the translocation of assimilates to roots، which in turn enhanced root growth characters such as root dry matter، root depth، root area and total root length.