Effects of epiphytic diatom Licmophora paradoxa on photosynthesis, malondialdehyde content and antioxidant enzymes activities of Pyropia yezoensis

Abstract

This study investigated the effects of epiphytic diatom <em>Licmophora paradoxa</em> on the physiological activities of <em>Pyropia yezoensis</em>, including photosynthesis, malondialdehyde (MDA) content and antioxidant enzymes activities. The photosynthetic activity was measured using chlorophyll fluorescence technology. Physiological indexes, such as chlorophyll-<em>a</em>, MDA content, antioxidant enzymes superoxide dismutase (SOD), and catalase (CAT) were determined by spectrophotometry. The results showed that photosynthetic parameters, the maximum quantum efficiency of PSII (<em>F</em>_v/<em>F</em>_m), the maximum electron transport rate (rETR_max), the minimum saturating irradiance (<em>E</em>_k) and Chl-<em>a</em> content decreased in <em>P. yezoensis</em>, which had been previously attached by the diatom <em>L. paradoxa</em>. On the other hand, physiological indexes of the resistance mechanism, such as MDA content, SOD and CAT antioxidant enzymes activities were significantly increased in the host <em>P</em>. <em>yezoensis</em>. It is concluded that epiphytic diatoms created adverse effects on the photosynthesis of <em>P. yezoensis</em>, and stimulated the physiological responses of <em>P. yezoensis </em>to epiphytes. This study is beneficial/ helpful to better understand the relationship between epiphytic microalgae and host macroalgae.