Effects of Antitranspirant Spray and Potassium: Calcium: Magnesium Ratio on Photosynthesis, Nutrient and Water Uptake, Growth, and Yield of Sweet Pepper

ABSTRACT

Sweet pepper plants (Capsicum annuum L.) were cultivated hydroponically under different nutrient cation ratios at both high potassium (K)/calcium (Ca) (12:2) or magnesium (Mg)/Ca (4:2) ratios, compared with half strength Hoagland's solution (K:Ca:Mg; 3.5:2:0.5). Additionally, antitranspirant (Pinolene) was sprayed every fortnight to the aerial part of the plant at 1% (v/v). The antitranspirant (AT) did not affect dry weight accumulation in the leaves, stems, roots, total plant leaf area, or leaf dry weight percentage. Net carbon dioxide (CO₂) assimilation was not impaired by the AT but the water uptake was reduced significantly independent of the nutrient solution used. The AT did not affect the cation uptake but high Mg significantly reduced Ca concentration in leaves, stems, and fruits, whilst high K had an effect only in old leaves and fruits. The AT reduced fructose and glucose concentration in the leaves but no effect was found in the fruits. Fruit yield was not affected by AT, but it was increased when plants were grown with high Mg/Ca. The percentage of blossom-end rot was reduced with the AT, whilst it was increased with the solutions having high K/Ca or high Mg/Ca. The AT significantly reduced fruit firmness in high Mg/Ca and control solution but no effect was found for fruit color, shape index, total soluble solids, or pericarp thickness.

Keywords:

• Capsicum annuum L.
• cation ratio
• soluble carbohydrates
• transpiration
• fruit quality

ACKNOWLEDGMENTS

We gratefully acknowledge D.J. Walker for correction of the English. J. S. Rubio was the recipient of a doctoral fellowship. This research was supported by the INA project RTA2005-00087-C02-01 from the Spanish Ministry of Science and Innovation.