Effects of seed size on growth, development and yield of monogerm sugar beet

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Abstract
SUMMARY Samples of monogerm sugar-beet seed which had been cleaned but not processed, contained fruits weighing 2–27 mg and true seeds weighing 0·2–5·0 mg with seed weight averaging about 20% of fruit weight. Increasing fruit size by round hole sieving resulted in progressively greater percentage emergence. Radiography revealed that one reason for this improvement was that more locules were completely filled, and fewer contained shrivelled seeds or were empty. Commercial processing of one seed lot eliminated some but not all of the empty fruits or those containing poorly developed seeds. In the field, seedling size and root:shoot ratio increased with increasing seed size. Thus at equivalent plant densities, sugar yields were less from the smallest seed than from other grades because of the combined effects of less total growth and a less efficient partitioning of assimilates. Although improvements in establishment with increasing size grading were progressive, sugar yield at comparable plant densities was greater only from medium grades relative to the smallest grades, whilst yields from large and medium grades were similar. This difference was maintained irrespective of length of growing season or plant density.