Barley and its environment. 5. Stability of grain weight.
Barley cv. Proctor grown over a wide range of conditions had a relatively stable mean weight/grain of 34.9 ( plus or minus 2.84) mg (range 29.3-41 mg) and grain yield was strongly dependent on the number of grains/unit ground area. Results from NIAB field trials with spring barley cv. Zephyr, Sultan, Julia and Midas also revealed a fairly stable mean weight/grain for each cultivar, although Zephyr was the most variable. The variations in mean weight/grain were primarily related to the weather during the different growing seasons and required investigation because of implications for grain quality and yield. Proctor and wheat cv. Insignia 49 maintained a stable mean weight/grain by the translocation from the stem to the grain of a variable amount of assimilate formed before anthesis. The amount of this translocation was simply estimated from dry weight measurements of the standing crop, stem and ear. This analysis was substantiated by measurements of individual organ photosynthesis in crops of Proctor grown at Sutton Bonington in 1970 and 1972, and showed that under extreme conditions Proctor provided 70% of the final grain weight by translocating material assimilated before anthesis.