ABA mediates the response of grape leaf tissues to UV-B radiation

BERLI F.; MORENO D.; HESPANHOL-VIANA L.; BRESSAN-SMITH R.; BOTTINI R.

Puerto Vallarta

Congreso; XIX International Plant Growth Substances Association (IPGSA) Meeting; 2007

IPGSA

The UV-B radiation affects growth and development in plants, especially by a well documented effect on nucleic acids. In grapes, it is assumed that UV-B promotes metabolic changes that lead to an increased amount of substances related with the flavor of the wine. Our hypothesis is that ABA is involved in the grape plant responses to UV-B. An experiment was performed in which UV-B, ABA and tungstate (W, ABA aldehyde oxidase inhibitor) treatments were combined in a factorial design. ABA stimulated leaf pigments (chlorophylls a and b, and carotenes) respect to W, but only with significant differences under an UV-B filtered solar radiation (SR). UV-B showed determinant for higher levels of flavonoids, and both flavonoids and anthocyanin levels were enhanced by ABA as compared to W, but only under enriched (double of the normal content) SR and not when the UV-B was filtered. UV-B did not show effects per se on the activity of 4 enzymes involved in antioxidant response, namely CAT, APX, SOD and GPX. CAT and GPX activities were pharmacologically enhanced either under enriched- and filtered-UV-B SR, but the response was elicitated by both ABA and W. APX activity increased only with ABA in UV-B enriched SR. Conversely, SOD activity was inferior in ABA- and W-treated plants under enriched UV-B SR. These preliminary results suggest that ABA intermediates the plant-cell responses to UV-B.