Translocation from flowering to daughter tillers in perennial ryegrass (Lolium perenne L.)

Abstract

Recent New Zealand cultivars of Lolium perenne often have a high rate of tiller death and replacement in late spring–early summer. A majority of the new tillers are daughter tillers of flowering tillers. Previous research has led to a hypothesis that defoliation may influence the amount of assimilate exported by flowering tillers, and hence the rate of daughter tiller formation.

To test this hypothesis, flowering tillers of flowering tillers of L. perenne (cv. Ellett) were fed 740 kBq 14CO2 in late spring, then subjected to different light levels and defoliation treatments and harvested a month later, with attached daughter tillers, and radiocarbon allocation to and distribution within the daughter tillers determined. Daughter tiller formation from flowering tillers was greatest where seed heads were decapitated at the flag leaf node, and was reduced when the seed head was left intact or when the seed head was removed at ground level. At harvest, approximately 3.5% of recovered radiocarbon was located in daughter tillers. However, due to the smaller size of the daughter tillers, their specific activities were up to 15% of those in the parent tillers. Moreover, leaf segments of daughter tillers, which had been elongation zones at the time of labelling, exhibited localised specific activity approximately 3 times that in the remainder of the daughter tiller. Increased daughter tiller production by flowering tillers decapitated at the flag leaf node was associated with increased radiocarbon recovery from those daughter tillers.