Annals of Botany 40: 785-793, 1976
© 1976 Annals of Botany Company
RESEARCH-ARTICLE |
The Influence of Source of Photosynthate and Sink Size on Grain Yield in Oats (Avena sativa L.)
Agronomy Department, McGill University, Macdonald College Quebec, Canada
Received: 27 October 1975
Experiments were conducted using leaf defoliation and floret emasculation techniques to study sourcesink relationships in the spring oat cultivars Clintland 60 and Garry. Grain yield decreased more with leaf lamina removal at panicle emergence than at anthesis. Removing the penultimate leaf reduced yield at least as much as removing the flag leaf, indicating the relative importance of the penultimate leaf in oats. Removing the flag and penultimate leaves together at panicle emergence, or all leaves, lowered grain yield by 40 per cent, primarily due to the development of fewer grains. Similar defoliation at anthesis reduced yield by 20 per cent, due mainly to lower single grain weights. While there was some evidence of compensation effects in Clintland 60, lower leaves were unable to compensate for removal of flag and penultimate leaves. Grain filling depended upon an adequate photosynthetic area in the upper portions of the plant.
Increases in individual grain weights were obtained when grain number per panicle was reduced 40 per cent or more by emasculation. Increases in single grain weights did not compensate for loss in numbers. The potential capacity of the grains to accumulate assimilates was not fully exploited under normal field conditions. Straw weight did not increase and total plant dry weight decreased with lower grain numbers, indicating a lower than normal rate of production of assimilates.