Photosynthesis and kaempferol yields of soybean leaves under ABA application and mechanical wounding

Authors: RATNAYAKA, HARISH - Xavier University; Boue, Stephen; DINH, T. - Xavier University; LEE, S. B. - Xavier University; CHERUBIN, R. - Xavier University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2018
Publication Date: 5/12/2018
Citation: Ratnayaka, H., Boue, S.M., Dinh, T., Lee, S., Cherubin, R. 2018. Photosynthesis and kaempferol yields of soybean leaves under ABA application and mechanical wounding. Crop Science. 6:215. https://doi:10.4172/2329-9029.1000215.
DOI: https://doi.org/10.4172/2329-9029.1000215

Interpretive Summary: Environmentally sound plant treatments that can impose mild physiological stress and elicit bioaccumulation of useful phytochemicals such as kaempferols (low molecular weight flavonoids) are limited. We tested abscisic acid (ABA) foliar applications and two types of leaf wounding, piercing or hole punching in young greenhouse-grown soy plants. The effects of these treatments on leaf biology and chemistry were examined. While ABA treatments and leaf holing had no effect on pigment concentrations, leaf piercing increased total chlorophyll 39% and total carotenoids 38% compared to control. Although all leaf treatments appeared to increase antioxidant activity, only the 25% increase by ABA-treated plants compared to control was significant. Six kaempferols quantified were found to be mono-, di- and triglycosides. Each leaf treatment increased total kaempferol concentrations ranging from 42% in ABA-treated plants compared to control. However, the differences among kaempferol concentrations across leaf treatments were insignificant. Kaempferol yields showed positive correlations to net photosynthesis in ABA-treated plants. ABA application and wounding showed different influences on the balance between photosynthetic primary metabolism and kaempferol glycoside accumulation in soy leaves. Both ABA application and wounding are promising, eco-friendly leaf treatments that elicit kaempferol bioaccumulation in young soy leaves.

Technical Abstract: Environmentally sound plant treatments that can impose mild physiological stress and elicit bioaccumulation of useful phytochemicals such as kaempferols are limited. We tested abscisic acid (ABA) foliar application, 100 or 200 µM, and two types of leaf wounding, piercing or hole punching in young greenhouse-grown soy plants. Leaf gas exchange and A/Ci response, quantum yield, pigments and antiradical activity were measured using the same leaf and leaf kaempferol yields were measured in the leaf above. ABA 200 µM treatment reduced gas exchange characteristics including net photosynthesis by 20% or more and electron transport rate by 17%, but increased rubisco carboxylation and RuBP regeneration compared to control. ABA 200 µM-treated plants had 55% and 100% more stomatal limitation on net photosynthesis and quantum yield than control. Leaf-wounded plants, especially the leaf-pierced plants, showed the lowest stomatal limitation on either net photosynthesis or quantum yield, although they had the same gas exchange, electron transport, rubisco carboxylation and RuBP regeneration as the control. While ABA treatments and leaf holing had no effect on pigment concentrations, leaf piercing increased total chlorophyll 39% and total carotenoids 38% compared to control. Although all leaf treatments appeared to increase antiradical capacity, only the 25% increase by ABA 100 µM-treated plants compared to control was significant. Six kaempferols quantified were found to be mono-, di- and triglycosides. Each leaf treatment increased total kaempferol concentrations ranging from 42% in ABA 100 µM to 68% in ABA 200 µM-treated plants compared to control. However, the differences among kaempferol concentrations across leaf treatments were insignificant. Kaempferol yields showed positive correlations to net photosynthesis in ABA100 µM-treated plants and to stomatal conductance in ABA 200 µM-treated plants but a negative correlation to net photosynthesis in leaf-pierced plants. ABA application and wounding showed different influences on the balance between photosynthetic primary metabolism and kaempferol glycoside accumulation in soy leaves. Both ABA application and wounding are promising, eco-friendly leaf treatments that elicit kaempferol bioaccumulation in young soy leaves.