No description available.

No description available.

Young barley seedlings (Hordeum vulgare L.) were stressed using nutrient solutions containing NaCl or polyethyleneglycol (PEG) and measurements were made of leaf growth, water status, proline soluble sugar contents of growing (basal) and non-growing (blade) tissues. Leaf growth ceased within seconds following exposure of seedlings to osmotic solutions with water potential values (ψ) = -3 to -11 bars but growth resumed after a lag period. Latent periods were increased and new growth rates were decreased as ψ of nutrient solutions were lowered. Growth ceased before detectable changes occurred in tissue water status but leaf basal tissues began to adjust osmotically, and reductions of 1 to 2 bars in both ψ and osmotic potential (π) usually occurred for the first 1 to 2 hours with lower reduction rates thereafter. After 1 to 3 days exposure of seedlings to solutions with different ψ, cumulative leaf elongation was reduced as the ψ of the root medium was lowered. Reductions in ψ and π of tissues in leaf basal regions paralleled growth reductions, but turgor (P) was largely unaffected by stress. In contrast, ψ, π and P of leaf blades were usually changed little regardless of the degree and duration of stress, and blade ψ were always higher than ψ of basally located cells. It is hypothesized that blades have high ψ and are generally unresponsive to stress because water in most of the mesophyll cells in this area does not exchange readily with water present in the transpiration stream. Measurements of proline contents in different sections of leaf following water stress, showed that in living tissues proline levels are dynamically related to water status of the tissue. In the basal regions where reductions in ψ and π occurred rapidly, proline levels were elevated quickly, whereas, accumulation of proline in mid-blade tissues occurred slowly and in lower concentrations. The combined data of many experiments showed a strong correlation between proline levels and tissue ψ (r = 0.93) and π (r = 0.85). Increase in total soluble sugars (TSS) and ion concentrations, contributed significantly to the stress-induced osmotic adjustment observed in the growing tissue.

Plant growth regulator(s) (PGR) can be used as lodging inhibitors and/or yield promoters for spring barley (Hordeum vulgare L.). From 1987 to 1990 four field experiments were conducted to monitor barley main-stem apical development and to determine the effects of chlormequat (CCC) and ethephon on the development, physiology and yield of spring barley. Our data provide a description of barley apical development and the general pattern of leaf and spikelet primordium production under field conditions. In general, PGR treatment reduced the apical dominance of dominant sinks allowing the survival and greater development of more subordinate sinks. Early application of either CCC or ethephon retarded development of the main-stem apex from shortly after application to the awn elongation stage and reduced the number of aborted spikelet primordia, thus increasing the potential number of grains per spike and sometimes grain yield. Ethephon applied at ZGS 39 reduced plant height and lodging. Early application (ZGS 30) of ethephon, alone or in combination with CCC increased the number of spikes m$ sp{-2},$ but not grain yield. The number of spike-bearing shoots per unit area or per plant was increased by early PGR treatment, primarily by enhancement of tiller number rather than tiller survival. Early application of CCC or ethephon to spring barley is not justified, and caution must be taken when using ethephon at the currently recommended rate and stage for lodging control. Post-anthesis application of ethephon can efficiently enhance grain fill and yield of spring barley.

No description available.

Bibliography: leaves 187-216.

Bibliography: leaves 187-216 / xxi, 216 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1987