Effects of sulphur supply on the morphology of shoots and roots of alfalfa (Medicago sativa L.)

A sulphur (S)-deficient top soil was used in a pot experiment to investigate the effect of S supply on shoot and root growth and development in alfalfa (Medicago sativa L.). The treatments consisted of three rates of addition of S: 0, 20 and 40 mg kg(-1) soil and each was replicated four times. Alfalfa was harvested at 15, 30, 45, 60 and 75 d after seedling emergence. By the end of the experiment, plants with S supply had a significantly larger leaf area, heavier leaf, shoot and root dry weight per pot than controls. The effects of adding S also significantly increased plant height, basal stem diameter, chlorophyll concentration of young leaves, root length and root surface area compared with controls. The effects of S were greater on shoots than on roots. The ratio of root to shoot dry weight was 0.47 when S was supplied and 0.88 without added S, indicating that c. 0.32 and 0.47 of the total net photosynthate, produced with or without S supply, respectively, were used for the development of roots. Overall, overcoming S deficiency resulted in a significant increase in shoot and root growth.