Nitrate Assimilation and Growth of Steptoe Barley and one of its Nitrate Reductase Deficient Mutants

Barley (Hordeum vulgare L. cv. Steptoe) and a nitrate reductasedeficient mutant (narla) were grown in a nutrient film systemwith three concentrations of nitrate. Comparisons were madewith respect to growth, yield, activities of enzymes of nitrateassimilation and accumulation of nitrate and total nitrogen.In nutrient film, grain yeild of the wild-type was greater thanthat of narla. for any treatment. Nitrate reductase activitiesof narla, measured in vivo, were higher than might be expectedin an NR-deficient mutant both in leaves and especially in roots.In all treatments, narla accumulated more nitrate than did thewild-type. No significant genotypic differences were observedin nitrite reductase or glutamine synthetase activities. Whenthe two genotypes were grown in soil (i.e. when availabilityof nitrate to the roots was less than in nutrient film) differencesin growth were insignificant. Hordeum vulgare L., mutant, nitrate status, assimilation and accumulation, growth, yield     

A matrix population model analysis for the tropical tree,Araucaria cunninghamii

The temporal stability of estimates of demographic behaviour for a sample population of the tropical rainforest gymnosperm Araucaria cunninghamii was analysed using a stage-classified (Lefkovitch) matrix model. Previously published life-table analyses, which used only 2 years of held data (1975–77), were compared with life-table analysis based on a further 5 years of field data for growth and survival (1977–82). The new analysis calculated the finite rate of natural increase, λ, as 1.009 ± 0.077. This value is closer to the theoretical value of 1.0 for a stable population than is the value calculated on the basis of only 2 years of field data (1.021 ± 0.093). However, the two estimates are not significantly different from each other or from a value of 1.0. Despite the similarity of estimates for λ, the life-table analysis based on 5 years of data showed some marked differences from the earlier analysis. Revised growth and survival rates imply a slower progression to reproductive maturity and shorter reproductive life for A. cunninghamii. The predicted stable stage distribution (SSD) showed a better fit to the initial stage distribution (ISD), and bulges in the frequency distribution for large trees can be explained by the varying rates at which individuals grow from one stage to the next. The relative contributions of survival, growth and fecundity to the observed population growth rate (elasticity) remained similar for both analyses. Survival rate contributes most significantly to the achieved population growth rate, and this appears typical of long-lived plant species. However, the pattern of elasticities across size-classes changed for the new analysis and identified different critical life history stages from those recorded previously. Elasticity is proposed as a measure for classifying species using the competitive (C), stress-tolerant (S) and ruderal (R) model of plant strategies.