Tiller Senescence Research Articles

Tiller Bud Inhibition by Young Foliage Leaves in Jointing Wheat1

Young foliage leaves have been associated with bud inhibition in dicotyledonous plants. Whether or not young leaves influence tiller buds in a grass is important, and particularly so in species repeatedly mown or grazed for herbage since the regrowth arises primarily from new tillers. ‘Sonora 64’ wheat (Triticum aestivum L.) during the jointing stage possessed the tiHering characteristics desired for this investigation.The influence of removing selected leaf laminae on stems retaining the shoot apex was studied on plants in the greenhouse and on uprooted culms in growth chambers. Basal axillary buds on these culms were exposed by stripping off the sheaths of lower leaves. The greatest bud elongation was obtained on culms devoid of foliage leaf blades. Less bud elongation occurred in the presence of an intact flag leaf, and still less if several of the younger leaves retained laminae. On plants in the greenhouse, removal of the younger leaves delayed tiller senescence,i ncreasedt he numbeorf tillers surviving the heading stage, and resulted in the resumption of tillering after heading. These responses were indicative of conditions favoring tiller growth. Tiller bud elongation in Sonora 64 was suppressed on culms retaining the younger foliage leaves. Such leaf influence should be considered among the factors regulating tillering.

Tiller Senescence and Grain Development in Barley1

Two near‐isogenic barley cultivars segregating for male sterility were employed to study tiller senescence. This plant material made possible the simultaneous comparison of fruiting and nonfruiting plants without resort to debudding or mechanically removing flowers or fruits. The number of living tillers and tiller mortality was similar in fertile and sterile plants until some 10 days after awn emergence. Between jointing and awn emergence, extensive tiller senescence occurred in fertile and in sterile plants alike. This senescence is not attributable to the mobilization of nutrients into the developing fruit. The triggering mechanism for the preheading shoot senescence appears to be operative at initial stages of floral development and before mechanical debudding is feasible. Ten days to 2 weeks after awn emergence, new tillers arose rapidly on the male‐sterile plants. Renewed tillering on the fertile plants was delayed an additional 3 weeks.