不同水分条件下两种叶状地衣的光合活性对冻融交替的响应

冻融交替是我国北方常见气候现象,其对地衣光合作用的影响尚不清楚。研究了采自雾灵山的卷叶点黄梅Flavopunctelia soredica和平盘软地卷Peltigera elisabethae的光合活性(以净光合速率表示,net photosynthetic rate,Pn)对冻融处理的响应及其与地衣体含水量(干冻组:含水量<20%干重;湿冻组:含水量>200%)和物种的关系。结果显示卷叶点黄梅的干冻组Pn经5次冻融后下降至对照的21%,湿冻组经3次冻融后下降至负值,平盘软地卷的干冻组和湿冻组在5次冻融后Pn均为负值;相对净光合速率(relative net photosynthetic rate,Rpn)与冻融次数的线性回归分析表明,卷叶点黄梅湿冻组的斜率绝对值(58.06)>平盘软地卷湿冻组(41.01)>平盘软地卷干冻组(32.27)>卷叶点黄梅干冻组(11.44)。结果表明冻融胁迫可显著抑制两种地衣的光合活性,这种抑制作用具有物种差异且和地衣体内水分含量有关:水分含量的增高将增强冻融胁迫对地衣光合活性的抑制作用;干燥状态下,卷叶点黄梅的低温耐性远高于平盘软地卷,但在湿润状态下则低于后者。两种地衣对冻融循环的光合响应的物种差异与其微生境气候有关:生长于较干燥开阔地带的卷叶点黄梅与生于阴湿生境中的平盘软地卷相比,可能已形成了更强的低温干燥适应能力,其低温湿润适应能力则较弱。全球气候变化可能会通过冻融事件的时空格局的改变而对地衣的光合作用和分布造成负面影响。     

三种地卷响应Cu~(2+)胁迫的差异分析

基于谷胱甘肽(Glutathione,GSH)含量变化和铜吸附性分析地卷、平盘软地卷和犬地卷响应Cu~(2+)胁迫的差异,以了解谷胱甘肽在低等生物地衣抗重金属胁迫中的作用。分光光度法和火焰原子吸收方法分别测定地衣体的GSH与细胞内、外的铜含量。结果显示,低浓度Cu~(2+)胁迫下,3种地卷GSH均呈上升趋势,4 mmol/L时达最高;5-8 mmol/L时,地卷和犬地卷的GSH逐步下降较明显,但仍显著高于对照组,而平盘软地卷GSH在3-5 mmol/L Cu~(2+)范围差异不显著,Cu~(2+)5 mmol/L时才出现较明显的下降(P0.05)。4 mmol/L Cu~(2+)处理时间不同时,犬地卷的GSH变化与处理时间正相关,而地卷和平盘软地卷的GSH出现波动式变化(6 h增加,12 h下降,18-24 h上升)。3种地卷胞外铜与Cu~(2+)浓度和处理时间呈正相关并显著高于胞内铜(P0.01),而胞内富集的铜与地衣GSH变化相对应呈高-低-高的变化趋势。菌藻共生的特殊生物-地卷类似于高等植物可诱导合成GSH缓解胁迫产生的伤害,3种地卷的铜耐受性差异与其铜吸附性和GSH合成能力密切相关。     

哀牢山山地森林不同附生地衣功能群的水分关系和光合生理特征

附生地衣是热带和亚热带山地森林生态系统中重要的结构性组分, 在生物多样性保护、环境监测、养分循环中发挥着重要作用。附生地衣按共生藻、生活型和繁殖策略的不同可划分为不同的功能群, 不同附生地衣功能群的分布格局存在较大的差异, 然而其生理生态机制仍不清楚。该研究以我国西南地区哀牢山亚热带山地森林中的附生地衣优势类群为研究对象, 对该地区蓝藻地衣、阔叶地衣、狭叶地衣及枝状地衣4种功能群的8种附生地衣的水分关系、光合生理特征等进行了测定分析, 结果显示: 不同功能群附生地衣的持水力和失水速率均存在差异, 其中蓝藻地衣具有较高的最大水分含量, 而枝状地衣的失水速率较快; 过高和过低的水分含量都会抑制附生地衣的光合作用, 但抑制程度有所差异; 蓝藻地衣的光合作用最适水分含量比较高, 表明它们的光合生理活动对水分条件要求较高, 所以它们偏好潮湿的生境, 同时蓝藻地衣的光补偿点比较低但光饱和点却不低, 反映出它们具有较宽的光强适应范围, 所以蓝藻地衣能够同时分布于强光和弱光生境中; 枝状地衣的光合最适水分含量较低, 表明它们的光合生理活动对水分条件要求不是很高, 能够适应较为干旱的环境, 同时枝状地衣的光补偿点和光饱和点都很高, 说明它们的光合生理活动对光照条件要求比较高, 所以它们广泛分布于强光生境中; 阔叶和狭叶地衣的光补偿点比较高, 说明它们更适应有充足光照条件的生境。     

毛竹光合作用对环境因子的季节响应

采用Li-6400测定毛竹光合作用对光照强度、CO2浓度、温度和湿度等环境因子响应的季节变化,结果表明:毛竹最大净光合速率、光补偿点、光饱和点、光合量子效率的年均值分别为7.30、19.15、1075mmol.m-2.s-1,0.032;最大净光合速率夏季>秋季>冬季>春季;春季的光补偿点最高,夏季次之,而秋季和冬季均较小;光饱和点与光合量子效率的季节变化均为秋季>夏季>冬季>春季。毛竹CO2补偿点、CO2饱和点、羧化效率的年均值分别为73.52、1500μmol.mol-1,0.033。CO2补偿点春季>冬季>秋季>夏季;CO2饱和点春季>秋季>夏季>冬季;羧化效率夏季>秋季>冬季>春季。毛竹光合最适温度均在20～30℃,光合最适温度在春、秋季与实验前3天最高气温的平均值十分接近,而夏、冬季与测定前10天的最高气温平均值较为接近,光合最适温度在春、秋两季相当,夏季稍高,冬季最低。光合最适湿度为40%～65%,季节变化趋势:秋季>夏季>冬季>春季。总体而言,毛竹光合作用对环境因子的季节响应与环境因子的季节变化、叶片的生理活性密切相关。     

六种叶状体苔藓植物叶绿素含量和光合效率研究

以六种叶状体苔藓为材料,通过测定叶绿素含量及实际光合量子产量,检验叶状体苔藓植物叶绿素含量与实际光合量子产量之间的关系。结果表明,六种叶状体苔藓总叶绿素含量中值6.06 mg·g-1,其中花叶溪苔Pellia endiviifolia最高(9.72 mg·g-1),楔瓣地钱Marchantia emarginata最低(4.46 mg·g-1);叶绿素a/b值变化范围1.61～2.04,林氏黄角苔Phaeoceros carolinianus最高,毛地钱Dumortiera hirsuta最低;紫背苔Plagiochasma rupestre、楔瓣地钱和蛇苔Conocephalum conicum实际光合量子产量明显高于毛地钱、花叶溪苔和林氏黄角苔。叶状体苔藓叶绿素含量与其实际光合量子产量之间并非简单的线性关系,气室结构及生境可能影响其实际光合效率。这一结论进一步丰富了苔藓植物对光照的生态适应理论。     

西藏高原濒危植物西藏巨柏光合作用日进程

研究采用目前先进的光合作用测定系统L i-Cor-6400测定濒危物种西藏巨柏的光合作用,自然环境条件下的西藏巨柏光合日进程表现为单峰型曲线,在12:00时左右达到最高峰,其光合作用不存在“午休现象”。在12:00时,西藏巨柏的气孔限制值和水分饱和亏缺分别达到最大值,此时的水分利用效率较高,在9:00时,西藏巨柏获得一天中最大的表观量子效率,水分利用效率达到最大值。其蒸腾速率在13:00时最大,这个时间并不与光合速率最大值同步,这说明在西藏特殊的气候环境条件下,影响光合速率的因素很多。在光合速率的日进程中,高光合速率值(大于4.00μm o lCO2/(m2.s))持续时间在5h左右,这使得西藏巨柏的光合作用产物得以有效积累,也为西藏巨柏在半干旱环境中的生长创造了有利条件。     

不同年代推出的冬小麦品种叶片气体交换日变化的差异

选择 6 0年来北京地区广泛种植的 3个冬小麦 (TriticumaestivumL .)品种 ,在相同的环境条件下种植。为了研究它们的产量与单位叶面积的净光合速率 (Pn)的关系 ,测定了不同生育期Pn、蒸腾速率 (Tr)的日变化 ,并用Pn/Tr计算叶片瞬时的水分利用率 (WUE)。结果表明 :单位叶面积净光合速率与产量之间的关系随生育期不同而变化。在拔节期高产品种“京冬 8号”(九十年代推出 )的光合速率和蒸腾速率在一天中总是最高 ,一天中差异最大时 ,分别比低产品种“燕大 1817”(四十年代推出 )高 77%和 6 9%。而其水分利用率却小于低产品种。这种差异随小麦的生长发育而变化 ,一般上午 10 :0 0前“京冬 8号”的光合速率较高 ,而 10 :0 0后“燕大 1817”的光合速率较高。到腊熟期 ,低产品种“燕大 1817”的光合速率在一天中始终最高。蒸腾速率的变化规律与光合速率相似 ,然而“燕大1817”叶片的水分利用率一般最高。与现代推出的品种不同 ,老品种“燕大 1817”叶片的光合作用午休现象不明显 ,说明它可能具有一定的抗光氧化性。我们认为 ,在品种改良的过程中 ,叶片光合作用的潜力可能有所提高 ,但它的抗光氧化性可能减弱。     

作物光合、蒸腾与水分高效利用的试验研究

通过田间试验,对作物光合、蒸腾、气孔行为及其影响因素进行了研究。结果表明,光合与蒸腾的非线性关系可以用抛物线方程表述,其中光合速率最高时的蒸腾速率为临界值,超出该值即为奢侈蒸腾,干旱处理的临界值较低,通过合适的调控措施,抑制奢侈蒸腾并不影响光合生产,综合分析光合速率、蒸腾速率与气孔导度的关系,气孑L导度大于0．12mol·m^-2·s^-1,实施提高气孔阻力并抑制蒸腾的措施,既节约水分又促进光合作用,增加产量．光合速率基本上随光合有效辐射的增加而提高,并有光饱和点存在,水分条件影响叶片光合作用达到饱和的早晚,干旱处理的光饱和点远远低于湿润处理,强光需要水分充足相耦合,才能充分发挥光能利用率,蒸腾与辐射的线性关系十分显著。从光合有效辐射入手,在光合有效辐射大于1000μmol·m^-2·s^-1时实施措施,既可大大降低蒸腾,又可改善光合,节水增产效果不言而喻。     

橡胶林下益智光合特性的季节动态变化

利用农林复合模式发展生态农业可提高资源利用效率, 橡胶(Hevea brasiliensis)-益智(Alpinia oxyphylla)间作模式是橡胶园最主要的农林复合模式。该研究通过野外原位定位实验, 研究不同季节橡胶林下环境因子对益智光合作用的影响, 并进一步分析益智光合作用与主要环境因子的关系。结果表明: (1) 3月益智净光合速率日变化为“V”形曲线, 14:00降到最低值; 而6月、9月和12月益智净光合速率日变化趋势为10:00达到最大值, 随后缓慢降低; 在雨季(6月和9月)蒸腾速率的日平均值和日最高值均显著高于旱季(3月和12月)。表明林下益智在不同季节均能维持植株正常生长, 且表现出了较强的适应能力。3月土壤水分亏缺造成益智叶片气孔导度降低, 使其净光合速率维持在较低的水平。(2)通过光响应曲线修正模型计算出益智叶片各光合响应参数, 发现3月最大净光合效率和光饱和点显著低于6月、9月和12月; 而光补偿点和暗呼吸速率却显著高于6月、9月和12月, 表明3月土壤水分亏缺导致益智光合酶活性降低, 而表现出光抑制现象, 同时呼吸强度加剧, 光合能力显著下降。(3)采取相关分析发现, 3月气温与净光合速率显著负相关, 空气湿度与净光合速率显著正相关, 高温和低湿度共同限制了益智的光合作用; 而9月和12月, 林下光合有效辐射是益智光合作用的限制因子。     

不同年代推出的冬小麦品种叶片气体交换日变化的差异

选择60年来北京地区广泛种植的3个冬小麦( Triticum aestivum L.)品种,在相同的环境条件下种植.为了研究它们的产量与单位叶面积的净光合速率( Pn ) 的关系,测定了不同生育期 Pn 、蒸腾速率( Tr )的日变化,并用 Pn / Tr 计算叶片瞬时的水分利用率( WUE ).结果表明:单位叶面积净光合速率与产量之间的关系随生育期不同而变化.在拔节期高产品种"京冬8号"(九十年代推出)的光合速率和蒸腾速率在一天中总是最高,一天中差异最大时,分别比低产品种"燕大1817"(四十年代推出)高77%和69%.而其水分利用率却小于低产品种.这种差异随小麦的生长发育而变化,一般上午10:00前"京冬8号"的光合速率较高,而10:00后"燕大1817"的光合速率较高.到腊熟期,低产品种"燕大1817"的光合速率在一天中始终最高.蒸腾速率的变化规律与光合速率相似,然而"燕大1817"叶片的水分利用率一般最高.与现代推出的品种不同,老品种"燕大1817"叶片的光合作用午休现象不明显,说明它可能具有一定的抗光氧化性.我们认为,在品种改良的过程中,叶片光合作用的潜力可能有所提高,但它的抗光氧化性可能减弱.     

Production of several isoforms of β-1,4-glucanase by the cyanolichen Peltigera canina

Lichen cellulase may participate in the degradation of the external substrata and/or modification of the photobiont cell wall. To promote a better understanding of the roles of cellulases in lichens, a cyanolichen was chosen because of the absence of cellulose in its symbionts. Freshly-collected thalli of Peltigera canina (L.) Wild, produce β-1,4-glucanase (EC 3.2.1.4, β-1,4-D-glucanohydrolase). This enzyme's activity was detected in the soluble and cell wall fractions and it was found to be secreted to the incubation medium when thalli were floated on water or on cellobiose. Several forms of the enzyme were detected by isoelectrofocusing. In preparative isoelectrofocusing, a single peak was obtained in each fraction, characterized by pls of 5.05, 5.25 and 4.75 in the soluble, cell wall and medium fractions, respectively. These differences were in agreement with the different pattern of bands obtained in slab-isoelectrofocusing, where the most acidic band (pl of 4.45) was present only in the soluble fraction and the band with higher pl (6.17) was more intense in the cell wall fraction. Since both symbionts in a cyanolichen lack cellulose, cellulases cannot participate in the modification of their cell wall; the presence of cellulase in Peltigera canina must therefore be related to the degradation of the tissues of the moss substratum.     

Sarcosine: a possible regulatory compound in the Peltigera praetextata-Nostoc symbiosis

Abstract In analyses of free amino acids in the lichen Peltigera praetextata high levels of sarcosine ( N -methylglycine) were found.
Sarcosine was found to stimulate nitrogenase activity of the cyanobiont Nostoc , isolated from Peltigera canina . This stimulation was optimal at 1 mM sarcosine, a concentration which is close to that calculated as being present in a water-saturated lichen thallus. Sarcosine also was found to inhibit the activity of glutamine synthetase in Nostoc . This inhibitory effect may account for the stimulation of nitrogenase activity and may be important in the symbiotic regulation of cyanophilic lichens.     

Cyanobiont specificity in some Nostoc-containing lichens and in a Peltigera aphthosa photosymbiodeme

The cyanobacterial symbionts in some Nostoc -containing lichens were investigated using the nucleotide sequence of the highly variable cyanobacterial tRNA^Leu (UAA) intron. When comparing different Nostoc -containing lichens, identical intron sequences were found in different samples of the same lichen species collected from two remote areas. This was true for all species where this comparison was made ( Peltigera aphthosa (L.) Willd., P. canina (L.) Willd. and Nephroma arcticum (L.) Torss.). With one exception, a specific intron sequence was never found in more than one lichen species. However, for two of the species, Peltigera aphthosa and Nephroma arcticum , two different cyanobionts were found in different samples. By examining a P. aphthosa photosymbiodeme it could be shown that the same Nostoc is present in both bipartite and tripartite lobes of this lichen. It is thus possible for one cyanobiont/ Nostoc to form the physiologically different symbioses that are found in bipartite and tripartite lichens. The connection between photobiont identity and secondary chemistry is discussed, as a correlation between differences in secondary chemistry and different cyanobionts/ Nostoc s in the species Peltigera neopolydactyla (Gyeln.) Gyeln. was observed. It is concluded that more knowledge concerning the photobiont will give us valuable information on many aspects of lichen biology.     

Rates of photosynthesis of two lichens and of their isolated algal components

Abstract

The rate of photosynthesis of two lichen species (Peltigera leucophlebia and Ramalina farinacea) was found to be 30 to 40% that of spinach leaf dises and 20% that of the free-living alga Chlorella when the results were expressed on a per mg chlorophyll basis. When the algae were isolated from the thalli, the rate of photosynthesis per mg chlorophyll increased for Ramalina farinacea and decreased for Peltigera leucophlebia. Product analysis indicated that the products of photosynthesis depended on the association of the alga with the fungus: algae isolated from the thalli showed a «shift» in products from sugars and sugar alcohols. to compounds such as organic acids. The results suggest that a symbiotic relationship with a fungus alters both the rate and products of algal photosynthesis.     

Effects of lichen heteroglycans on proliferation and IL-10 secretion by rat spleen cells and IL-10 and TNF-alpha secretion by rat peritoneal macrophages in vitro.

Four polysaccharides Pc-1, Pc-2, Pc-3 and Pc-4 were isolated from water and alkali extracts of the lichen Peltigera canina using ethanol fractionation, gel filtration and preparative HP-GPC. The monosaccharide composition was determined by methanolysis and GC and showed mannose and galactose as the predominating structural units. The mean M(r) was determined by HP-GPC. The heteroglycans were tested for in vitro immunomodulating activities and showed mitogenic activity in rat spleen cell proliferation assay and stimulated IL-10 secretion. In rat peritoneal macrophages, the heteroglycans stimulated TNF-alpha secretion, but not IL-10 secretion. These results indicate that the polysaccharides influence cells of the immune system both from the innate and the adaptive systems.     

十二种地卷目地衣固氮活性的种间差异

地卷目地衣是对许多生态系统的氮素循环具有重要影响的固氮类群,但其固氮活性的种间差异研究甚少。将不同产地和不同馆藏时间的12种地卷目地衣于相同条件下培养,即：亚石胶衣Collema subflaccidum、亚黑胶衣C. subnigrescens、坚韧胶衣C. tenax、裸果猫耳衣Leptogium hildenbrandii、猫耳衣L. menziesii、柄猫耳衣L. pedicellatum、土星猫耳衣L. saturninum、黑猫耳衣L. trichophorum、犬地卷Peltigera canina、分指地卷P. didactyla、裂芽地卷P. praetextata和地卷P. rufescens。以乙炔还原法（acetylene reduction assay）于培养1d、10d和15d测定其固氮活性,结果显示所有地衣的固氮活性在培养10d与15d之间差异不显著,表明经过至多10d的培养后地衣固氮活性即可完全恢复;培养10d和15d的固氮活性平均值表现出显著的种间差异（P＜0.001）：黑猫耳衣Leptogium trichophorum固氮活性最高[（4.532±0.368）μmol C2H4/gdw·h],约为犬地卷Peltigera canina的2倍[（2.349±0.223）μmol C2H4/gdw·h];其他10种地衣固氮活性大致相近。显示地衣固氮作用的可塑性较大,是地衣具有较强适应能力的又一例证。     

中国宁夏六盘山的地卷目地衣(英文)

从宁夏六盘山区的多个生境中采集了隶属于地卷目(Peltigerales)3科5属的16种地衣,分别为环纹瓦衣(Coccocarpia erythroxyli)、球胶衣(Collema coccophorum)、坚韧胶衣珊瑚变种(C.tenaxvar.corallinum)、砖孢胶衣(C.subconveniens)、亚石胶衣(C.subflaccidum)、亚洲猫耳衣(Leptogiumasiaticum)、伯尔特猫耳衣(L.burneti-i)、猫耳衣(L.menziesii)、土星猫耳衣(L.saturninum)、犬地卷(Peltigera canina)、平盘软地卷(P.elisabethae)、多指地卷(P.polydactylon)、裂芽地卷(P.praetextata)、地卷(P.rufescens)、双孢散盘衣(Solorina bispora)和凹散盘衣(S.saccata)。其中,亚洲猫耳衣和伯尔特猫耳衣为中国北方新分布种,球胶衣为中国西北新分布种,其余13种均为宁夏新记录种。地卷目地衣在六盘山区分布稀少,且表现出对较为阴湿生境的偏好。     

Photosynthetic CO2-use efficiency in lichens and their isolated photobionts: the possible role of a CO2-concentrating mechanism

The CO₂ dependence of net CO₂ assimilation was examined in a number of green algal and cyanobacterial lichens with the aim of screening for the algal/cyanobacterial CO₂-concentrating mechanism (CCM) in these symbiotic organisms. For the lichens Peltigera aphthosa (L.) Willd., P. canina (L.) Willd. and P. neopolydactyla (Gyeln.) Gyeln., the photosynthetic performance was also compared between intact thalli and their respective photobionts, the green alga Coccomyxa PA, isolated from Peltigera aphthosa and the cyanobacterium Nostoc PC, isolated from Peltigera canina. More direct evidence for the operation of a CCM was obtained by monitoring the effects of the carbonic-anhydrase inhibitors acetazolamide and ethoxyzolamide on the photosynthetic CO₂use efficiency of the photobionts. The results strongly indicate the operation of a CCM in all cyanobacterial lichens investigated and in cultured cells of Nostoc PC, similar to that described for free-living species of cyanobacteria. The green algal lichens were divided into two groups, one with a low and the other with a higher CO₂-use efficiency, indicative of the absence of a CCM in the former. The absence of a CCM in the low-affinity lichens was related to the photobiont, because free-living cells of Coccomyxa PA also apparently lacked a CCM. As a result of the postulated CCM, cyanobacterial Peltigera lichens have higher rates of net photosynthesis at normal CO₂ compared with Peltigera aphthosa. It is proposed that this increased photosynthetic capacity may result in a higher production potential, provided that photosynthesis is limited by CO₂ under natural conditions.     

Phycotype pairs in Nephroma, Peltigera and Lobaria in Norway

Green and blue–green phycotype pairs formed by the lichens Nephroma arcticum (L.) Torss., Peltigera aphthosa (L.) Willd., P. britannica (Gyelnik) Holt.–Hartw. & Tønsb. comb. nov. and Lobaria amplissima (Scop.) Forss. are reported, and their possible occurrence in Peltigera venosa (L.) Baumg. is considered. A blue–green phycotype of Nephroma arcticum is reported for the first time. The taxonomy, chemistry and distribution of the Peltigera aphthosa group in Norway are discussed.