摘要：
在有性繁殖时期,潮间带海藻羊栖菜(Hizikia fusiformis)的叶状体与生殖托遭受低潮干出脱水的影响.为阐明羊栖菜在有性繁殖时期不同部位对干出脱水的耐受能力,研究了羊栖菜的叶状体和雌、雄生殖托在干出脱水过程中以及随后的沉水恢复状态下叶绿素荧光动力学参数变化.实验结果表明,羊栖菜叶状体及其生殖托的PS Ⅱ有效光化学量子产量[Y(Ⅱ)]分别在0-73％和0-60％的脱水率范围内未发生显著变化,而继续脱水则会显著降低藻体的Y(Ⅱ),表明羊栖菜叶状体和生殖托的Y(Ⅱ)下降的脱水界限值分别为73％和60％,对脱水耐受能力较强.在连续干出脱水过程中,叶状体和生殖托的最大相对电子传递速率(rETRm.)和光强耐受能力(Ik)都显著下降,且在严重脱水状态(失水率为75％)下,羊栖菜叶状体和雌、雄生殖托的Y(Ⅱ)分别比干出初始时降低了12％、31％和37％,且复水后其雌、雄生殖托的Y(Ⅱ)无法恢复,甚至持续降低.同时叶状体和生殖托的rETRmax、1k和光能利用效率(α)都显著下降,说明严重脱水使藻体不同部位的PSⅡ反应中心受到了不可逆的损伤.在持续大幅度脱水过程(失水率高于60％)中及随后的沉水恢复过程中,比较藻体各部位的Y(Ⅱ)值发现,叶状体＞雌生殖托＞雄生殖托,表明严重脱水对雄生殖托的影响最大,对叶状体的影响最小.在有性生殖阶段,为了羊栖菜能有性繁殖成功,应避免藻体,尤其是生殖托经受到严重的干出脱水胁迫.%The fronds and reproductive tissues (female and male receptacles) of intertidal-grown Hizikia fusiformis exposed to air and faced desiccation when the tide is low during sexual reproduction period.In this study,we determined photosystem Ⅱ (PS Ⅱ) effective quantum yield [Y(Ⅱ)] and the parameters of rapid light curves of desiccation tissues:fronds,and female and male receptacles,at different desiccated states.We also measured Y (Ⅱ) of desiccation tissues upon rewetting after 50％ and 75％ water loss.Our objective was to reveal whether there are differences of desiccation tolerance or not among fronds and reproductive tissues of H.fusiformis when exposed to air during sexual reproduction period.The results showed that Y(Ⅱ) exhibited no significant changes within the range of 0-73％ water loss from fronds,and within the range of 0-60％ water loss from female and male receptacles.However,the values of Y(Ⅱ) were sharply reduced with the water loss more than 73％ in fronds,and more than 60％ in receptacles.Severe dehydration of 75％ water loss reduced Y(Ⅱ) values by 12％,31％,and 37％ in fronds,and female and male receptacles,respectively.The values of Y(Ⅱ) of submersed tissues (fronds and receptacles) followed by 50％ always remained high levels.However,the values of Y (Ⅱ) of both severe-desiccated female and male receptacles could not recover,and continued to decrease even after re-submersion,suggesting that the PS Ⅱ reaction center in receptacles of H.fusiformis underwent irreversible damage when water loss reached up to 75％.Our results showed that PS Ⅱ reaction center in fronds of H.fusiformis exhibited greater desiccation tolerance of than that in receptacles.The maximum relative electron transport rates (rETRmax),light use efficiency (α),and the tolerance of high irradiance (Ik) for emersed fronds and receptacles of H.fusiformis exhibited no significantly differences at the initial desiccation state.Both rETRmax and Ik decreased significantly with increased water loss.Particularly,rETRmax were reduced by 33％,67％,and 78％ in fronds,and female and male receptacles,respectively,after 75％ of water loss.Furthermore,α were hardly affected by 50％ of water loss,but it were reduced by 16％,42％,and 59％ of their initial value when fronds,and female and male receptacles lost 75％ water,respectively.The values of Y(Ⅱ),rETRmax,Ik,and α of the fronds were higher than those of the receptacles,and the parameters of the female receptacles were always higher than those of the male receptacles after 60％ water loss of desiccation tissues under emersed state,and the results showed the same trends when followed by submersed state.Those indicated that male receptacles were the most susceptible,while the fronds were relative less susceptible by severe dehydration.It was concluded that severe desiccation is an important factor affecting the reproduction success of H.fusiformis during the sexual reproduction period,and the factors alleviating desiccation such as sea spray and shingle-overlapping would benefit the emersed fronds and receptacles of H.fusiformis.
