Boron as limiting factor in photosynthesis and growth of sunflower plants in relation to phosphate supply
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The effect of varied boron supply (0, 0.5, 1, 25 and 100 mu M) in the nutrient solution containing different phosphate concentrations on nutrient utilization, plant growth and photosynthesis was studied in young sunflower (Helianthus annuus L.) plants, Boron deficiency decreased the dry matter yield of plants, leaf area and chlorophyll content in the leaves. The decrease was significantly higher in the presence of sub-(0.1 mM) and supra-optimal phosphate concentrations (3 mM) in the nutrient solution. Boron deficiency appreciably decreased photosynthetic oxygen evolution per unit leaf area and proton gradient across the thylakoid membrane, but it did not influence photochemical and electron transport efficiency of photosystem two. The diminished rate of photosynthesis in boron-deficient sunflower leaves could be correlated to the reduction in chlorophyll content, electron transport to CO2 and photophosphorylation. In P-deficient plants nonphotochemical chlorophyll fluorescence quenchin...g increased with baron concentration, implying an increase in the proton gradient, and confirming the role for boron in maintaining the integrity of thylakoid membranes.
Source:Agrochimica, 1997, 41, 3-4, 144-154
- PISA UNIV PRESS, PISA