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

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 A degrees C, but was highly vulnerable to 28 A degrees C. During 8 days of culture, the thalli grew at 8 -aEuro parts per thousand 17 A degrees C, and growth was higher at 8 A degrees C. Thalli with water loss a parts per thousand currency signaEuro parts per thousand 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 a parts per thousand yenaEuro parts per thousand 45 %. Removal of surface water and moderate water loss significantly increased photosynthesis recovery from 1 day of -20 A degrees C freezing, and the maximum recovery (80 % P (n) and 97 % F (v)/F (m)) occurred in the thalli with water loss of similar to 30 %. During 10 days of culture, thalli maintained active photosynthesis and growth under salinity 22.6-36.6; however, those in salinity a parts per thousand currency signaEuro parts per thousand 7.8 or a parts per thousand yen50.6 lost fresh weight, while those in salinity a parts per thousand currency signaEuro parts per thousand 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.