高寒灌丛草甸生态系统CO2释放的初步研究

以金露梅(Potentilla fruticosa)灌丛草甸生态系统为对象，应用静态密闭箱-气相色谱法对高寒灌丛(GG)、丛内草甸(GC)和裸地(GL)的CO2释放进行了初步研究。结果表明：GG、GC和GL CO2的释放速率均呈明显的单峰型日变化进程，最大释放速率出现在15：00～17：00之间，最小值在7：00前后出现，白天释放速率大于夜晚；CO2释放速率具有明显的季节性变化特征，生长期CO2释放速率明显高于枯黄期，且均表现为正排放，8月为CO2释放高峰期，释放速率GG>GC>GL(P<0．01)；2003年6月30日至2004年2月28日，高寒灌丛植被-土壤系统CO2释放量为3088．458±287．02g／m^2，丛内草甸植被-土壤系统CO2释放量为2239．685±183．68g／m^2，其中基础土壤呼吸CO2的释放量约为1346．748±176．24g／m^2，分别占GG和GC释放量的43．61％和60．13％；CO2释放速率的日变化主要受地表和5cm地温制约，而季节动态与5cm地温呈显著正相关关系(P<0．01)。

可可西里地区藏羚的社群特征

藏羚(Pantholops hodgsoni)的集群类型有雌性群、雄性群、母仔群、雌雄混群和独羚5种形式。2002年7月～2003年12月，在可可西里地区沿青藏公路设立试验区，直接观察到936群次，计13795只次藏羚。藏羚的集群类型受到生育周期的影响，季节间差异显著。春季以雌性群(60．49％)和雄性群(30．86％)为主；夏季和秋季主要为雌性群(41．65％，49．66％)和母仔群(49．36％，33．67％)；雌雄混群(58．14％)主要出现在冬季。雄性群在1年中很少见，尤其是夏秋两季，冬季较为常见，多由亚成体雄性组成。独羚是一种特殊的集群类型，占11．32％。常见的集群大小为2～20只，占71．90％，其次是21～200只的群，占16．35％；>200只的集群极少，仅占0．43％，且仅出现于夏季产羔往返迁徙途中。藏羚的集群大小受竞争、捕食风险以及迁徙繁殖的共同影响。藏羚的集群极不稳定，交配期雌雄混合群受雄性亚成体的干扰经常改变，而在迁徙季节大群和小群之间的转换也很频繁。大型集群为雌性群或母仔群，其最适集群大小为2～20只。

Molecular cloning, expression and biochemical property analysis of AtKP1, a kinesin gene from Arabidopsis thaliana

Kinesins are common in a variety of eukaryotic cells with diverse functions. A cDNA encoding a member of the Kinesin-14B subfamily is obtained using X-RACE technology and named AtKP1 (for Arabidopsis kinesin protein 1). This cDNA has a maximum open reading frame of 3.3 kb encoding a polypeptide of 1087 aa. Protein domain analysis shows that AtKP1 contains the motor domain and the calponin homology domain in the central and amino-terminal regions, respectively. The carboxyl-terminal region with 202 aa residues is diverse from other known kinesins. Northern blot analysis shows that AtKP1 is widely expressed at a higher level in seedlings than in mature plants. 2808 bp of the AtKP1 promoter region is cloned and fused to GUS. GUS expression driven by the AtKP1 promoter region shows that AtKP1 is mainly expressed in vasculature of young organs and young leaf trichomes, indicating that AtKP1 may participate in the differentiation or development of Arabidopsis thaliana vascular bundles and trichomes. A truncated AtKP1 protein containing the putative motor domain is expressed in E. coli and affinity-purified. In vitro characterizations indicate that the polypeptide has nucleotide-dependent microtubule-binding ability and microtubule-stimulated ATPase activity.

Characterization of photosynthetic pathway of plant species growing in the eastern Tibetan plateau using stable carbon isotope composition

The photosynthetic pathway of plant species collected at Menyuan, Henan, and Maduo sites, east of Tibetan Plateau, China, during the growing season were studied using stable carbon isotopes in leaves. The 232 samples leaves analyzed belonged to 161 species, 30 families, and 94 genera. The delta(13)C values (from -24.6 to -29.2 %o) indicated that all the considered species had a photosynthetic C-3 pathway. The absence of plant species with C-4 photosynthetic pathway might be due to the extremely low air temperature characterizing the Tibetan Plateau. The average delta(13)C value was significantly (p < 0.05) different between annuals and perennials at the three considered study sites. Hence the longer-lived species had greater water-use efficiency (WUE) than shorter-lived species, that is, longer-lived species are better adapted to the extreme environmental conditions of the Tibetan Plateau.