条斑紫菜丝状体不同发育时期对光照和温度的光合适应能力

Effects of Light Intensity and Temperature on Photosynthetic Adaptability of the Different Stages of Pyropia yezoensis Free-Living Conchocelis

中文关键词: 紫菜  营养藻丝  孢子囊枝  光合作用  高温  高光

英文关键词: Pyropia  Vegetative conchocelis  Conchosporangial branches  Photosynthesis  High light intensity  High temperature

中文摘要:

      以条斑紫菜(Pyropia yezoensis)丝状体为材料，研究温度(15℃、25℃和35℃)与光强[40、100和300 μmol/(m2·s)]对营养藻丝和孢子囊枝光合生理的影响。结果显示，15℃和25℃实验组中，营养藻丝和孢子囊枝的PSⅡ原初光能转化效率(Fv/Fm)、总光合速率(Pg)和净光合速率(Pn)均随光强升高而降低。在300 μmol/(m2·s)下，营养藻丝的Fv/Fm和Pg趋于零，Pn为负值。在25℃、40 μmol/(m2·s)下，营养藻丝的呼吸耗氧速率(Rd)在实验周期内一直显著高于孢子囊枝；其他组则随胁迫时间延长，二者间Rd差距逐渐缩小。总体上，在相同条件下，所测孢子囊枝Fv/Fm、Pg和Pn均显著高于营养藻丝，而Rd与营养藻丝相当。35℃实验组在6 h时，孢子囊枝的Fv/Fm显著高于营养藻丝，但随光强升高直线下降(P<0.05)，其他组Fv/Fm均趋于0。在40、100 μmol/(m2·s)下，6 h时，孢子囊枝Pg和Rd高于营养藻丝或二者相当；在300 μmol/(m2·s)下，后期营养藻丝Pn和Rd高于孢子囊枝，但在整个实验周期，二者的Pn均为负值。总体上，营养藻丝和孢子囊枝的Fv/Fm、Pg和Pn均显著低于(多数趋于0或负值)15℃和25℃，而35℃的Rd高于15℃和25℃；后期，2种藻丝均出现发绿变白，甚至死亡现象。研究表明，在条斑紫菜营养藻丝的光合作用被严重抑制的光强、温度条件下，孢子囊枝仍具备相对高的光合活力，说明在温度和光强升高到不利于营养藻丝生长的情况下，刺激藻丝转向了孢子囊枝发育阶段，后者具备适应更高温度和光照的能力。

英文摘要:

      The photosynthetic physiology of the different stages of the Pyropia yezoensis free-living conchocelis were investigated at different temperatures (15℃, 25℃, and 35℃) and light intensities [40, 100, and 300 μmol/(m2·s)] to reveal the regulation mechanism and establish a foundation for efficient and accurate P. yezoensis seedling technology. The main results were as follows: 1) At 15℃ and 25℃, the optimum PSⅡ quantum yield (Fv/Fm), gross photosynthesis rate (Pg), and net photosynthetic rate (Pn) of the vegetative conchocelis and conchosporangial branches decreased as light intensity increased. Fv/Fm and Pg of the vegetative conchocelis filaments dropped to zero under 300 μmol/(m2·s) light intensity, and the values of Pn were below zero. The respiratory oxygen consumption rate (Rd) of the vegetative conchocelis was significantly higher than that of the conchosporangial branches at 25℃ and 40 μmol/(m2·s). The difference in the Rd values between vegetative and conchosporangial branches decreased gradually during culturing under the other conditions. In general, Fv/Fm, Pg, and Pn of the conchosporangial branches were significantly higher than those of the vegetative conchocelis filaments and there was no significant difference in Rd between the two developmental stages under most culture conditions; 2) Fv/Fm of the conchosporangial branches was significantly higher than that of the vegetative conchocelis at 6 h of culture at 35℃, which decreased with increasing light intensities. Fv/Fm of the other treatments was nearly zero. Pg and Rd of the conchosporangial branches were higher than or equivalent to that of the vegetative conchocelis after 6 h of culture at 35℃, and 40 or 100 μmol/(m2·s). After 1 d or 2 d, Pn and Rd of the vegetative conchocelis were higher than those of the conchosporangial branches, while the Pn and Rd were all below zero under 300 μmol/(m2·s) conditions during the entire experimental period. Overall, Fv/Fm, Pg, and Pn of free-living P. yezoensis conchocelis were significantly lower (mostly zero or below), whereas Rd was higher at 35℃ than at 15℃ or 25℃. After 1~3 d, both vegetative conchocelis and conchosporangial branches became green or white. In summary, under the light intensity and temperature conditions in which the vegetative conchocelis was severely inhibited, conchosporangial branches had relatively high photosynthetic activity. The present findings indicated that high light intensity and temperature were not beneficial to vegetative conchocelis, but they could stimulate the vegetative conchocelis to turn into conchosporangial branches, and conchosporangial branches have greater resistance ability under high- temperature and light intensity stress.