Effect of phenological development on radiophosphorus translocation from leaves in crested wheatgrass.

The effect of phenological development on the pattern of photosynthate translocation was studied in crested wheatgrass [Agropyron cristatum (L.) Gaertn.] plants grown in a nursery under semi-natural environmental conditions at Logan, Utah. Radiophosphorus was used to trace the photosynthate translocation from April 13, 1968, through December 2, 1968.In early spring photosynthates were translocated about equally to the roots and younger leaves. Translocation was chiefly upward during the flower stage but was reversed with raturation of the inflorescence. In late summer the plants appeared quiescent but substantial 32P was transported to the underground portions of the plant. After quiescence was broken in the fall, shoot and root growth were resumed simultaneously with peak 32P movement to the crown and roots.The concentration of total available carbohydrates in the roots and crowns reached a maximum level just prior to quiescence and decreased during shoot production in the fall. Presumably, the carbohydrates were used in growth and the accumulation of carbohydrates for the winter is apparently not critical in crested wheatgrass. Since the plants have many basal leaves throughout the winter, they may have the capacity to carry out photosynthesis on warm, sunny winter days and are capable of immediately initiating growth in the spring.