Selection for height of nectar in the corolla tube of English singlecut Red Clover

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Abstract
SUMMARY Pollination of red clover by honey bees would be expected to increase if varieties could be produced in which the nectar is within 7 mm of the mouth of the corolla tube and so within the bee's reach. Pollination by honey bees in a small glasshouse increased the height of nectar in the resulting stock of red clover but when this was again pollinated by honey bees there was no further increase. Selection of plants with above average nectar height ultimately produced a stock in which the nectar height was 0·76 mm higher than in the original; a difference which was significant. There was also a considerable and significant increase in the proportion of florets with nectar within 7 mm of the mouth of the corolla tube. It was concluded that the height of nectar can be increased by selection; this would be of particular value for the pollination of red clover varieties with long corolla tubes grown for seed where there are insufficient numbers of bumble bees.