荒漠灌丛土壤动物分布及其生态功能

在干旱、半干旱荒漠生态系统中,灌丛作为一种重要的植被类型,其独特的形态和生理适应特性能够有效促进退化生态系统结构与功能的恢复。土壤动物是荒漠生态系统中不可或缺的重要组成部分,对促进灌丛"肥岛"演变具有重要的生态作用,有利于灌丛生态功能的发挥及退化生态系统的恢复。近年来,国内外学者对荒漠灌丛微生境土壤动物的研究逐步深入,取得大量的研究成果。在此基础上,首先综述荒漠灌丛微生境土壤动物群落分布和生态功能,总结灌丛与土壤动物分布间作用关系的数学模型,针对荒漠灌丛土壤动物研究中存在的问题提出了未来可能的研究方向和建议。     

Rice G protein γ subunit qPE9-1 modulates root elongation for phosphorus uptake by involving 14-3-3 protein OsGF14b and plasma membrane H+-ATPase

Heterotrimeric G protein is involved in plant growth and development, while the role of rice (Oryza sativa) G protein γ subunit qPE9-1 in response to low-phosphorus (LP) conditions remains unclear. The gene expression of qPE9-1 was significantly induced in rice roots under LP conditions. Rice varieties carrying the qPE9-1 allele showed a stronger primary root response to LP than the varieties carrying the qpe9-1 allele (mutant of the qPE9-1 allele). Transgenic rice plants with the qPE9-1 allele had longer primary roots and higher P concentrations than those with the qpe9-1 allele under LP conditions. The plasma membrane (PM) H⁺-ATPase was important for the qPE9-1-mediated response to LP. Furthermore, OsGF14b, a 14-3-3 protein that acts as a key component in activating PM H⁺-ATPase for root elongation, is also involved in the qPE9-1 mediation. Moreover, the overexpression of OsGF14b in WYJ8 (carrying the qpe9-1 allele) partially increased primary root length under LP conditions. Experiments using R18 peptide (a 14-3-3 protein inhibitor) showed that qPE9-1 is important for primary root elongation and H⁺ efflux under LP conditions by involving the 14-3-3 protein. In addition, rhizosheath weight, total P content, and the rhizosheath soil Olsen-P concentration of qPE9-1 lines were higher than those of qpe9-1 lines under soil drying and LP conditions. These results suggest that the G protein γ subunit qPE9-1 in rice plants modulates root elongation for phosphorus uptake by involving the 14-3-3 protein OsGF14b and PM H⁺-ATPase, which is required for rice P use.     

云南山楂茎尖的离体培养及其无性系快速繁殖

用云南山楂(Crataegus scabrifolia(Franch.)Rehd.)成年树茎尖和实生芽两种不同发育阶段的材料为外殖体,诱导它们休眠芽萌动,丛生芽条并诱导芽条生根。实验结果如下:1.以成年态的云南山楂侧芽为外植体,培养在附加IAA 0.1—0.5mg/l+6-BA 1-2mg/l的MS培养基上可诱导芽的萌发;将芽继代培养在附加0.5—1mg/l 6-BA的SH或MS培养基上,40天后芽数增殖4—6倍;将芽条截下置于1/2MS培养基上,附加不同浓度的IAA或IBA,可得到50—80％的生根率。2.以实生芽为外殖体,在相同条件下,则20天后芽数增殖便可获4—6倍;98％以上生根。结果表明:云南山楂的幼年态要比成年态易脱分化和再分化。     

香荚兰种子的无菌萌发试验

香荚兰(Vanilla planifolia)是兰科、香荚兰属植物,主产于湿热地区。香荚兰的果实是国际上重要的食用香料的原料。大约在1960年,我国引入香荚兰试栽。生产上,通常用扦插法繁殖;但如用种子繁殖,虽然结实较晚(约7至8年开始结实,较扦插苗晚4—5年),但结实期长,盛产期可维持约15年。而且,在杂交育种过程中,一定要用种子繁殖。     

N6-substituted 9-methyladenines: a new class of adenosine receptor antagonists

A series of 15 N6-substituted 9-methyladenines have been assessed as antagonists of A2-adenosine receptor-mediated stimulation of adenylate cyclase in membranes of human platelets and rat PC12 cells and of A1-adenosine receptor-mediated inhibition of adenylate cyclases in membranes of rat fat cells and as inhibitors of binding of N6-R-[3H]phenylisopropyladenosine to A1-adenosine receptors in rat brain membranes. N6 substitution can markedly increase the potency of 9-methyladenine at A1 receptors, while having lesser effects or even decreasing potency at A2 receptors. Effects of N6 substituents on adenosine receptor activity of the 9-methyladenines are reminiscent of effects of N6 substituents on activity of adenosine, suggesting that N6 substituted 9-methyladenines bind to adenosine receptors in the same orientation as do N6-substituted adenosines. N6-Cyclopentyl-9-methyladenine with Ki values at the A1 receptors of 1.3 microM (fat cells) and 0.5 microM (brain) is at least 100-fold more potent than 9-methyladenine (Ki 100 microM, both receptors), while at the A2 receptors KB values of 5 microM (platelets) and 25 microM (PC12 cells) make it 5-fold more potent and equipotent, respectively, compared to 9-methyladenine (KB 24 microM, both receptors). N6-Cyclopentyl and several other N6-alkyl and N6-cycloalkyl analogs are selective for A1 receptors while 9-methyladenine is the most A2 receptor selective antagonist. The N6-R- and N6-S-(1-phenyl-2-propyl)-9-methyladenines, analogous to N6-R- and N6-S-phenylisopropyladenosines, exhibit stereoselectivity at both A1 and A2 receptors. Marked differences in potency of certain N6-substituted 9-methyladenines at the A2 receptors of human platelets and rat PC12 cells provide evidence that these are not identical receptors.