Water deficit (WD), a major contributor to yield reductions in faba bean (Vicia faba), is a complex phenomenon that varies across daily to seasonal cycles. Several studies have identified various morphological and physiological indicators of WD tolerance, which generally show limited water use during WD. Limited information is available on the impact of WD on nutrient content and reproductive biology of the faba bean. We studied carbohydrates, amino acids, mineral nutrients and the abundance of naturally occurring carbon isotopes (δ13 C) in leaf and grain tissues of faba bean genotypes grown under well-watered (WW) and WD conditions. δ13 C of leaf tissues were found to indicate changes in water use due to WD but this was not reflected in grain tissues. Nutrient concentrations with regard to amino acids and minerals were not influenced by WD. However, carbohydrate accumulation was found to be significant for WD, specifically through the presence of a higher concentration of myo-inositol in WD leaf tissues. Alternatively, sucrose concentration in grain tissues was reduced under WD treatment. WD hampered reproductive functionality by reducing pollen viability and germination with the severity and duration of stress and this reduction was less prominent in the drought-tolerant genotype (AC0805#4912) compared to the sensitive one (11NF010c-4). It was also demonstrated that WD caused developmental impairment in the stamen and pistil, where the pistil appeared more sensitive than stamen. These findings suggest that WD impairs pollen viability and pistil function reducing yield volume, but the nutrient content of the resulting yield is not significantly affected.
© 2020 Scandinavian Plant Physiology Society.