TITLE:
Soybean Seed Phenol, Lignin, and Isoflavones and Sugars Composition Altered by Foliar Boron Application in Soybean under Water Stress
AUTHORS:
Nacer Bellaloui
KEYWORDS:
Boron Nutrition; Seed Lignin; Seed Phenolics; Isoflavones; Soybean
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.3 No.4,
April
18,
2012
ABSTRACT: Previous research showed that foliar boron (B) application at flowering or seed-fill growth stages altered seed protein, oil, and fatty acids. The objective of this research was to investigate the effects of foliar B fertilizer on seed phenolics (phenol, lignin, and isoflavones) and sugars concentrations. A repeated greenhouse experiment was conducted on soybean [(Glycine max(L.) Merr.)] under watered and water-stressed conditions. Soybean plants were divided into different sets, and each set was subjected to one of the following treatments: W = plants were watered with no foliar B; WB = plants were watered and received foliar B; WS = plants were water-stressed with no foliar B; WSB = plants were waterstressed and received foliar B. Foliar B was applied at rate of 0.45 kg/ha twice at flowering and twice at seed-fill stages. The results showed that total phenol and lignin concentrations were higher in seed collected from water-stressed plants compared with those collected from watered plants whether B was applied or not. The higher total phenol and lignin concentration in seed collected of water-stressed plants may be due to B-deficiency in plant tissues. Application of B resulted in higher concentrations of total seed B and isoflavones under watered and water-stressed plants. Higher cell wall B was higher in water-stressed plants than in watered plants, having an opposite trend to total B. Application of B resulted in higher seed sucrose in watered and water-stressed plants, but raffinose and stachyose were significantly higher under water-stressed plants. The research demonstrated that foliar B fertilizer altered seed phenol, lignin, isoflavones, and sugars, suggesting that B involved in phenolics and sugar metabolism. The higher cell wall B in waterstressed plants than in watered plants supports previous research that B has mainly a structural role. The higher sucrose resulting from foliar B in watered plants is desirable as sucrose contributes to seed quality. The increase of raffinose and stachyose concentrations in seed of water-stressed plants is undesirable as raffinose, and especially stachyose may be involved in water stress/drought tolerance. The current knowledge would help soybean breeders select for higher phenolic compounds and desirable sugars for higher seed qualities under drought conditions.