Influence of dew on biomass and photosystem II activity of cyanobacterial crusts in the Hopq Desert, northwest China
Influence of dew on biomass and photosystem II activity of cyanobacterial crusts in the Hopq Desert, northwest China
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DOI：
10.1016/j.soilbio.2009.06.005
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发表时间：
2009-12
影响因子：
9.7
通讯作者：
B. Rao;Yongding Liu;Weibo Wang;Chunxiang Hu;Li Dun-hai;S. Lan
中科院分区：
文献类型：
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作者：
B. Rao;Yongding Liu;Weibo Wang;Chunxiang Hu;Li Dun-hai;S. Lan
露水是半干旱和干旱地区荒漠生物的重要水源。通过野外和室内试验研究了露水对蓝藻结皮生物量增长和光合作用的影响。蓝藻微鞘藻Microcoleus vaginatus Gom.和爪哇胞藻Scytonema javanicum（Kütz.）出生与死亡，首先进行原培养和连续大量培养，然后于2007年夏末秋在中国西北部霍普曲沙漠进行了将接种物接种到流沙上形成蓝藻结皮的田间试验。测定结露量和叶绿素a含量，以评估结皮生物量的变化后露。此外，我们确定了光系统II（PSII）的活动在实验室中通过模拟干燥/再水化过程，由于露水的地壳。结果表明，以露水为唯一水源时，结皮生物量在初始接种叶绿素4.3 μg/cm-2沙至5.8 - 7.3 μ g/cm-2结皮之间波动，结皮生物量在初始接种叶绿素4.3 μg/cm-2沙至5.8-7.3 μg/cm-2结皮之间波动，结皮生物量在初始接种叶绿素4.3 μg/cm-2沙至5.8-7.3 μg/cm-2结皮之间波动，结皮生物量在初始接种叶绿素4.3 μ g/cm-2沙至5.3 μ g/cm-2结皮之间波动。并达到峰值约8.2微克叶绿素每厘米-2地壳由于植物。结露量与结皮含水量呈极显著正相关（r = 0.897或r = 0.882，均P < 0.0001），但与生物量相关不显著（r = 0.246或r = 0.257，均P > 0.05），表明露水对结皮生物量的调节作用有限。相应地，我们发现降雨显著促进了蓝藻结皮生物量的增加。复水后的模拟实验结果表明，在黑暗和5 °C条件下复水后50 min内，约80%的PSII活性可恢复，只有约20%的活性是光温依赖的。这可能意味着，即使在黎明前的低温和弱光条件下，露水对蓝藻结皮在干燥和复水过程中快速激活光合活性至关重要。研究还表明，蓝藻结皮对露水的吸收和固持能力强于沙粒，这取决于结皮的小气候特征和土壤性质。因此，充分认识露水对蓝藻结皮生长和活性的调节作用，并正确评价结皮在荒漠化防治中的潜在应用价值，是十分必要的。
Dew is an important water source for desert organisms in semiarid and arid regions. Both field and laboratory experiments were conducted to investigate the possible roles of dew in growth of biomass and photosynthetic activity within cyanobacterial crust. The cyanobacteria, Microcoleus vaginatus Gom. and Scytonema javanicum (Kütz.) Born et Flah., were begun with stock cultures and sequential mass cultivations, and then the field experiment was performed by inoculating the inocula onto shifting sand for forming cyanobacterial crust during late summer and autumn of 2007 in Hopq Desert, northwest China. Measurements of dew amount and Chlorophyll a content were carried out in order to evaluate the changes in crust biomass following dew. Also, we determined the activity of photosystem II(PSII) within the crust in the laboratory by simulating the desiccation/rehydration process due to dew. Results showed that the average daily dew amount as measured by the cloth-plate method (CPM) was 0.154 mm during fifty-three days and that the crust biomass fluctuated from initial inoculation of 4.3 μg Chlorophyll a cm−2sand to 5.8–7.3 μg Chlorophyll a cm−2crust when dew acted as the sole water source, and reached a peak value of approximately 8.2 μg Chlorophyll a cm−2crust owing to rainfalls. It indicated that there was a highly significant correlation between dew amounts and crust moistures (r = 0.897 or r = 0.882, all P < 0.0001), but not a significant correlation between dew and the biomass (r = 0.246 or r = 0.257, all P > 0.05), and thus concluded that dew might only play a relatively limited role in regulating the crust biomass. Correspondingly, we found that rains significantly facilitated biomass increase of the cyanobacterial crust. Results from the simulative experiment upon rehydration showed that approximately 80% of PSII activity could be achieved within about 50 min after rehydration in the dark and at 5 °C, and only about 20% of the activity was light-temperature dependent. This might mean that dew was crucial for cyanobacterial crust to rapidly activate photosynthetic activity during desiccation and rehydration despite low temperatures and weak light before dawn. It also showed in this study that the cyanobacterial crusts could receive and retain more dew than sand, which depended on microclimatic characteristics and soil properties of the crusts. It may be necessary for us to fully understanding the influence of dew on regulating the growth and activity of cyanobacterial crust, and to soundly evaluate the crust's potential application in fighting desertification because of the available water due to dew.