Abstract: Six spring wheat cultivars bred at different years in semi-arid regions were selected to comparatively study the numbers and morphological characteristics of their seminal root systems, and to analyse the relationship of these indexes with crop drought-resistance and yield production. The results show that in semi-arid regions of loess plateau, the cultivars had a growth redundancy of root systems, which was unfavourable to the yield production. With the lapse of breeding years, the cultivars tended to have less root, shorter root length, larger active root absorption area, and smaller diameter of metaxylem vessel of seminal roots. These features made the cultivars bred at recent years use water more savingly at their earlier vegetative growth period, and conserve certain amount of soil water to satisfy their water needs at flowering and seed-filling stages, and hence, enhance their yield production.

Key words: Spring wheat, Drought resistance, Root redundancy, Water transportation