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EFFECTS OF Ca AND P NUTRIENT LEVELS ON THE GROWTH OF N-FERTILIZED AND RHIZOBIUM-NODULATED PHASEOLUS VULGARIS L. SUBJECTED TO TWO CONTRASTING TROPICAL SOLAR RADIATION REGIMES AND SPRAYED WITH PROPYL GALLATE
Published online by Cambridge University Press: 28 November 2014
Summary
Interactions between two contrasting photosynthetic photon flux densities (PPFD) and increasing Ca and P concentrations were analysed in N-fertilised (+N) and Rhizobium-inoculated (+Rh) Phaseolus vulgaris plants grown for 30 days in glasshouses. Plants were grown in sand-filled Leonard jars with 0.9 L N-free for +Rh plants or plus 6 mM KNO3 for +N plants nutrient solution, pH 6.2 in the lower compartment, and were subjected to midday PPFD ≥ 1650 ≤ 1800 mmol m−2 s−1/37±2°C air temperature (HI/HT) or PPDF ≥ 900 ≤ 1200 μmol m−2 s−1/26±2°C air temperature (MI/MT). The nutrient solutions were supplied with 1, 2, 3 or 4 mM P in combination with 1 or 4 mM Ca. Results revealed a 100% mortality of the HI/HT+Rh plants at the juvenile stage of growth. Whereas, all HI/HT+N plants reached the preflowering stage but showed smaller shoot masses, lower chlorophyll concentrations, unusually high chlorophyll a/b ratios and higher shoot nitrate concentrations when compared to values in +N plants grown at MI/MT. Increasing concentrations of P and Ca, or the daily spray of leaves with 2 mM propyl gallate (Pg), did not counteract the negative effects of HI/HT on +Rh and +N plants. Maximum growth, nodulation, chlorophyll concentration and catabolism of ureides in leaves were exclusively observed in +Rh plants grown under MI/MT conditions and supplied with 2 mM P and 1 mM Ca. In contrast, the greater growth of +N plants, associated with higher chlorophyll and nitrate concentrations, took place at MI/MT conditions combined with 1 mM P and 4 mM Ca. Pg further enhanced the growth of MI/MT+Rh and MI/MT+N plants grown at P < 2 mM, at 1 or 4 mM Ca, respectively. At MI/MT, there was a positive relationship between leaf carotenoid concentration and growth of +Rh and +N plants.
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- Copyright © Cambridge University Press 2014
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