Abstract

MOSCO, Alessandro. Tissue localization of betacyanins in cactus stems. Rev. Mex. Biodiv. [online]. 2012, vol.83, n.2, pp.413-420. ISSN 2007-8706.

Betalains are soluble pigments found only in the suborder Chenopodiniae, while in all other Angiospermae they are replaced by anthocyanins. The convergent evolution of the presence of anthocyanins and betalains in vegetative tissues supports the hypothesis of a similar function, based on the absorption properties of these pigments. The screening effect of anthocyanins results in the reduction of the amount of photoinhibition. betalains, being the anthocyanin counterpart in most families of Caryophyllales, were also suggested to have a screening role. This study is aimed at identifying in which Cactaceae stem tissues betacyanins, reddish to violet betalain pigments, accumulate. Stem accumulation of betacyanins was observed in cacti both in their natural habitat and in cultivation. The localization of betacyanins was assessed by light microscope studies on tubercle transverse sections. During 2 field trips in distinct years to the Mexican plateau in March, many cactus species, belonging to different genera, were observed displaying a reddish stem. Light microscope studies on cultivated plants showed that betacyanins accumulate in the hypodermis and in the outer layers of the chlorenchyma, where they may act as a screen, thus protecting the photosystems present in the underlying chlorenchyma, and have a possible antioxidant function in the cortex.

Keywords : betacyanins; cacti; epidermis; hypodermis.

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