Nutrient uptake among subspecies of Cucurbita pepo L. is related to exudation of citric acid

Nutrient uptake among subspecies of Cucurbita pepo L. is related to exudation of citric acid

2005

A:PS

Exudation of organic acids by roots has been implicated in uptake of minerals from soil. Three cultivars within each of two subspecies of summer squash (Cucurbita pepo subsp. ovifera var. ovifera and C. pepo subsp. pepo var. pepo) were grown in the field in Hamden, Connecticut, USA, in 2002 and 2003. Plants of subsp. pepo had higher concentrations of K, P, and Zn than those of subsp. ovifera. These same cultivars were grown under P sufficient and depleted conditions in hydroponics, to measure exudation of organic acids from roots. When grown in hydroponics, tissues of subsp. ovifera had similar or higher concentrations of nutrients than subsp. pepo. Therefore, differences in tissue composition of field-grown plants are likely due to differences in nutrient uptake ability, not inherent differences in tissue composition between subspecies. P nutrition played a significant role in exudation of organic acids into the hydroponics solution. For both subspecies, P depletion resulted in exudation of more citric and succinic acid, and less oxalic and tartaric acid. Under P depletion, subsp. pepo exuded more citric acid than subsp. ovifera. When soil was eluted with solution containing root exudates, the exudates from subsp. pepo eluted more K, Mg, Fe, and Zn than did those from subsp. ovifera. Among subspecies of C. pepo, exudation of organic acids, particularly exudation of citric acid in response to P depletion, is associated with the plant's ability to accumulate more inorganic nutrients when grown in the field.

v.130(5):782-788, AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL

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