Influence of temperature and humidity on tripping of lucerne flowers

Abstract

Lucernes representing diverse indigenous habitats were studied over a range of temperatures and atmospheric humidities during flowering to investigate physical resistance of flowers to tripping. The amount of automatic flower tripping measured at 25°C varied from 1 to 14% of available flowers between lucernes. Studies of automatic tripping over a 20–40°C temperature range showed that most lucernes responded strongly to higher temperatures; but high latitude lucernes did not increase in automatic tripping.

A small reduction in relative humidity with constant temperature over the 20–40°C temperature range caused greatly increased automatic tripping in two Australian lucernes, but produced smaller increases in lucernes introduced from a similar latitude. It had no effect on high latitude lucerne.

At 25°C induced tripping, simulating the actions of pollen-collecting bees, showed differences in resistance to tripping between lucernes similar to those in automatic tripping. This pattern of differences may be related to that of seed production by these lucernes under field conditions, in south-eastern Australia.