PLANT-GROWTH AND NUTRIENT-UPTAKE CHARACTERISTICS OF FE-DEFICIENCY CHLOROSIS SUSCEPTIBLE AND RESISTANT SUBCLOVERS

The objective of this study was to evaluate the growth and nutrient-up take characteristics of Fe-deficiency resistant and susceptible subclo ver (Trifolium subterraneum L., T. yanninicum Katzn. and Morley, T. br achcalycinum Katzn. and Morley) cultivars on a calcareous soil. Ten su bclover cultivars showing varying susceptibilities to Fe-deficiency ch lorosis (Karridale, Nangeela, Geraldton, Mt. Barker, Woogenellup, Lari sa, Trikkala, Rosedale, Koala and Glare) were grown on a low-Fe, calca reous soil (Petrocalcic Paleustoll) under moist (18% water content, 85 % of water holding capacity) and water-saturated conditions using a Co ne-tainer(R)culture system. Chlorosis and its correlation with growth traits and mineral nutrition of the 10 cultivars were examined. The Fe -deficiency susceptibilities of the 10 cultivars decreased in the abov e order under the moist condition, but in slightly different order und er the saturated condition. Shoot and root dry weights, total dry weig ht, and root-to-shoot ratio were each negatively correlated with chlor osis under both soil-moisture conditions, as was total shoot content o f P, Ca, Fe, Mn and Zn. Shoot P and Fe concentrations were each positi vely correlated with chlorosis under the moist soil condition. Iron an d Cu utilization efficiencies (biomass per unit weight of nutrient) in the shoot were each negatively correlated with chlorosis under the mo ist soil condition. These results suggest that there may be several ch aracteristics of Fe-deficiency chlorosis resistance in subclovers, suc h as a more effective soil-Fe mobilizing mechanism(s), more balanced n utrition, lower required Fe concentration in the shoot, higher shoot-F e utilization efficiency, and higher root/shoot ratio under Fe-deficie ncy stress conditions.