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G. M. FLETCHER, J. E. DALE, Growth of Tiller Buds in Barley: Effects of Shade Treatment and Mineral Nutrition, Annals of Botany, Volume 38, Issue 1, January 1974, Pages 63–76, https://doi.org/10.1093/oxfordjournals.aob.a084802
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Abstract
Examination of the stem apex of Proctor barley showed that the bud of the coleoptile tiller, Tc, is probably present in the dry grain and that the bud, TI, carried in the axil of the first leaf is present at or soon after 24 h from planting. Subsequently tiller buds are initiated with a plastochron of about 4 days, this being rather longer than that for the foliar primordia. During the initial phase of bud growth vascular connections are established with the leaf above, but not to the subtending leaf. At some time after these vascular connections are formed and when it has a dry weight of 4–7 μg the bud enters a phase of rapid, exponential growth in dry weight.
Shading the first leaf delays the onset of rapid growth for both Tc and Ti, but after a lag period rapid growth commences; this is coincident with development of the second leaf as an organ exporting assimilated carbon.
The phase of rapid growth of tiller buds is delayed when application of either nitrogenous or nonnitrogenous minerals is delayed. Ammonium was found to be less satisfactory as a nitrogen source than nitrate, probably because of toxicity effects. Slight growth of Tc and T1 occurs in presence of nonnitrogenous minerals and absence of nitrogen but growth is greater when nitrogen is supplied in absence of the other minerals, although such growth is substantially less than that found when all nutrients are supplied. The interaction between nitrogen and non-nitrogenous minerals which controls bud growth was not found to affect growth of the parent plant which is, as previously shown, controlled by timing of the nitrogen supply. AnotheT distinction is that higher concentrations of nitrogen and the other minerals are required for maximum growth of the bud than for that of the plant.
Tiller bud growth is interpreted as occurring in two phases. In the first, initiation, phase there is a close association with the subtending leaf, and nutritionally bud and leaf are linked. This phase is followed by one in which the bud is directly connected by vascular traces to the leaf above, which because of this controls bud growth by modulating supply of assimilated carbon and nitrogen, and other minerals to it.
