Effect of abiotic stress on the gameophyte of Pyropia katadae var. hemiphylla (Bangiales, Rhodophyta)

Abstract

Pyropia germplasm qualified for drift system culture is highly applicable in China. The current farmed species are tolerant to abiotic stresses, but vulnerable without air drying. Pyropia katadae var. hemiphylla inhabits mid-intertidal marshes and is a candidate for drift-system farming. Here, the performance of the gametophytes under varying environmental conditions was investigated. The thalli endured a short period (<5 days) at 22°C, but was highly vulnerable to 28°C. During 8 days of culture, the thalli grew at 8−17°C, and growth was higher at 8°C. Thalli with water loss≤34 % recovered the optimum photochemical efficiency of PS II (F v /F m ) by up to 100 %, and the net photosynthetic rate (P n ) by over 70 %. This reduced to 50 % in the thalli with water loss≥45 %. Removal of surface water and moderate water loss significantly increased photosynthesis recovery from 1 day of −20°C freezing, and the maximum recovery (80 % P n and 97 % F v /F m ) occurred in the thalli with water loss of~30 %. During 10 days of culture, thalli maintained active photosynthesis and growth under salinity 22.6-36.6; however, those in salinity≤7.8 or ≥50.6 lost fresh weight, while those in salinity≤7.8 were characterized by reduced F v /F m , P n , and heavy thallus disruption. The above results indicated that P. katadae var. hemiphylla thalli adapted to low temperature, moderate desiccation, freezing, and salinity fluctuation. A farming strategy for this species is discussed.

Developmental and physiological properties of Pyropia dentata (Bangiales, Rhodophyta) conchocelis in culture

“…1c and 6c). P n is irradiancedependent Wang et al 2016) and, without exception, higher P n was obtained at higher irradiance in this study (Fig. 7c).…”

“…Once an organism is treated with temperatures higher than its endurance limit, F v /F m decreases significantly (Wang et al 2016). The vast drop in F v /F m at 31°C was a stress response (Fig.…”

“…The samples were placed in the dark for at least 15 min prior to measurement of F v /F m , which was recorded using a Diving Pulse Amplitude Modulation fluorometer (Diving-PAM, Walz, Germany) (Wang et al 2016). P n and R d were recorded using a Clark-type oxygen electrode (Hansatech Oxygraph, UK) in the same medium and at the same temperature as the treatments (Wang et al 2016).…”

“…P n and R d were recorded using a Clark-type oxygen electrode (Hansatech Oxygraph, UK) in the same medium and at the same temperature as the treatments (Wang et al 2016). The irradiance for measurement of P n was the same as the treatments and R d was recorded in darkness.…”

“…Long and intensive selective breeding of cultivated Pyropia leads to a reduction in genetic diversity of the stock, increased fragility to adversity, and decline in product quality. Therefore, it is crucial to recruit entirely new Pyropia species (Niwa et al 2009;Watanabe et al 2014;Green and Neefus 2015;Wang et al 2016). P. dentata has been cultivated on an experimental scale in Shantou, Guangdong province over the past few years (Xu et al 2013;Chen et al 2015).…”