Partitioning of Taproot Constituents and Crown Bud Development are Affected by Water Deficit in Regrowing Alfalfa (Medicago sativa L.)

Growth of alfalfa (Medicago sativa L.) following the correction of water deficits will depend, in part, on the amount of plant constituents available to support regrowth and the availability of crown buds for the development of new shoots. To investigate if water deficit affected the accumulation of taproot constituents and crown bud development of alfalfa, two alfalfa cultivars were exposed to increasing levels of water deficit (100, 75, 50 25 and 0% of the replacement water requirement) during a regrowth period. Shoot growth was reduced in proportion to the level of water deficit. Taproot starch concentrations decreased while taproot soluble sugar increased in plants exposed to a water deficit. Thirty-five d after initiation of treatments, taproot protein and amino acid concentrations were similar in all treatments that received water. Water deficit increased the relative concentration of low and middle molecular weight taproot vegetative storage proteins (VSP) and water deficits reduced the number and mass of green crown buds. Both cultivars had a similar response to water deficit for all taproot constituents and crown bud development. Further studies are required to determine the influence of increasing VSP abundance and decreasing numbers of crown buds on plant recovery following the removal of a water deficit. © Crop Science Society of America.