Showing papers by "Rana Munns published in 1999"
TL;DR: Salinity greatly advanced the time of floral initiation in the wheat cultivars, indicating that modification of apical development by salinity was not determined by salt in the apex itself, but mediated by signals or substrates derived from elsewhere in the plant.
Abstract: Two cultivars of wheat and two of barley differing in salt tolerance were grown at 0, 100 and 175 mM NaCl, and the development of the apex was followed as it turned from vegetative to reproduc- tive. Apices were taken for ion analysis when most of the spikelet primordia had been produced and the process of differentiation into floral organs was starting. K + concentrations in apices were unaffected by the salinity treatment, Na + concentrations were generally low in all treatments, below 50 mM, while Cl - levels were very low, below 30 mM. These levels of Na + and Cl - are too low to affect metabolism. In spite of these negligible effects on ion levels in the apex, salinity affected reproductive development: fewer spikelet primordia formed, and final spikelet numbers at ear emergence were reduced. Salinity greatly advanced the time of floral initiation in the wheat cultivars. This indicates that modification of apical development by salinity was not determined by salt in the apex itself, but mediated by signals or substrates derived from elsewhere in the plant.
135 citations
TL;DR: Results indicate that a reduced supply of water to the leaves and a supply of phosphorus that was bordering on deficient was not the cause of the growth reduction in seedlings with Rhizoctonia infection.
Abstract: Wheat seedlings infected with a pure inoculum of the root-rotting fungus Rhizoctonia solani were grown in pots designed to fit in pressure chambers, to allow the effects of the Rhizoctonia infection on leaf growth to be studied while maintaining the leaves at elevated water status. Wheat was grown to the third leaf stage in soil inoculated with three different levels of Rhizoctonia, and the pots were then pressurised for seven days to maintain the leaf xylem at the point of bleeding (ie. the leaves were at full turgor). The reduction in leaf expansion caused by Rhizoctonia was not overcome by pressurisation, indicating that a reduced supply of water to the leaves was not responsible for reduced leaf growth. The addition of phosphorus to pots marginally deficient in P did not increase the leaf growth of Rhizoctonia-infected plants, despite increased P uptake to the leaves. These results indicate that a reduced supply of water to the leaves and a supply of phosphorus that was bordering on deficient was not the cause of the growth reduction in seedlings with Rhizoctonia infection. The nature of this reduced growth remains uncertain but may involve growth regulators produced by the fungus, or by the plant as a result of the infection process. The mechanism of these growth reductions is of interest as it may provide a key to the development of plant resistance mechanisms.
23 citations