长期深淹对三峡库区三种草本植物的恢复生长及光合特性的影响

硬秆子草（Capillipedium assimile）、双穗雀稗（Paspalum distichum）和狗牙根（Cynodon dactylon）在经受与三峡水库水位运行节律基本一致的水淹时间和水淹持续时期,但淹水深度（0、5、15和25m）不同的处理后,对其进行了恢复生长和光合特性研究。结果表明：（1）3种草本植物之间相比,狗牙根的存活率最高,所有处理植株存活率达到了100％;硬秆子草和双穗雀稗随着水淹深度的增加,存活率呈降低趋势,5in深处理存活率达到了100％,15in和25m深处理存活率在80％以上。（2）3种草本植物恢复生长后的叶片净光合速率Pn、蒸腾速率Tr、气孔导度Gs、水分利用效率WUE和表观CO2利用效率CUEapp与未淹对照相比没有显著差异;不同物种相同水淹处理之间比较,狗牙根的各光合指标显著高于硬秆子草和双穗雀稗。（3）结合三峡库区消落带植被恢复物种筛选的基本条件和本试验不同处理植株的恢复生长及其光合特性的研究,结果表明,硬秆子草、双穗雀稗和狗牙根是能够忍耐长期深淹胁迫的、适宜于三峡库区消落带植被恢复与重建的优良物种。三者之间的耐淹能力从大到小依次为：狗牙根〉硬秆子草〉双穗雀稗。     

Effects of simulated submergence on survival and recovery growth of three species in water fluctuation zone of the Three Gorges reservoir

Paspalum distichum, Cynodon dactylon and Hemarthria altissima distribute widely in natural water fluctuation zone of the Three Gorges region. To investigate whether they are suitable for growing in the artificial water fluctuation zone, which has longer submergence time and different submergence rhythm, of the Three Gorges reservoir, three complete submergence depths (0.5, 1 and 2 m) were conducted for about 6 months (from 12 November 2007 to 30 April 2008), and the survival and recovery growth of the three species were recorded after re-emergence for two weeks. The three species could start recovery growth within one week and more than 50% plants could survive. Among the three species, P. distichum had the largest increments in branch number and maximum stem length, and the smallest root shoot ratio. C. dactylon, however, had the smallest maximum stem length increment, and its survival and branch number increment were both larger than those of H. altissima. For C. dactylon and H. altissima, the survival and branch number increment significantly increased, while maximum stem length increment tended to decrease when submergence depth went higher. For P. distichum, the survival and the shoot mass were the lowest after 2 m submergence depth, but the other parameters were not different among different submergence treatments. Compared with control plants, submergence increased root shoot ratio of C. dactylon and H. altissima, but did not affect that of P. distichum. These results demonstrated that the three species are submergence-tolerant and can be applied in vegetation reconstruction in water fluctuation zone of the Three Gorges reservoir. Meanwhile, the results also suggested that the three species developed different survival tactics during the long-term submergence.     

NaCl胁迫对杂交狗牙根品种‘苏植2号’和‘Tifgreen’生长及Na＋和K＋积累的影响

对0（对照）和20g·L-1NaCl胁迫条件下杂交狗牙根（Cynodondactylon×C.transvaalensis）品种‘苏植2号’（‘SuzhiNo.2’）和‘Tifgreen’不同部位的生长状况以及Na＋和K＋积累的差异进行了研究,并分析了2个品种间Na＋、K＋转运调控机制的差异。结果显示：在NaCl胁迫条件下,2个品种的叶片相对枯黄率、地下茎和根系的相对干质量、叶片和根系的Na＋含量和Na＋/K＋比以及钠钾选择性转运系数增加;修剪茎叶及冠层和地上部的相对干质量、植株相对总干质量以及叶片和根系的K＋含量均降低,但茎叶含水量无显著变化。NaCl胁迫条件下,不同土层中2个品种的根系相对干质量均不同程度增加,且20-40和40-60cm土层中根系干质量的增幅大于0-20cm土层;在0-20cm土层中2个品种根系的分配比例均有所降低,而在20-40和40-60cm土层中则不同程度提高。与‘Tifgreen’相比,NaCl胁迫条件下‘苏植2号’叶片相对枯黄率、Na＋含量和Na＋/K＋比更低,修剪茎叶及冠层和地上部的相对干质量、植株相对总干质量、叶片K＋含量和钠钾选择性转运系数更高;在20-40和40-60cm土层中‘苏植2号’根系相对干质量显著高于‘Tifgreen’,根系分配比例总体也高于‘Tifgreen’。综合比较结果表明：‘苏植2号’的抗盐性强于‘Tifgreen’,可能与其深层根系分配量更高和钠钾选择性转运能力较强有关。     

三峡库区消落带野生狗牙根对水淹适生性的转录组分析

为探究狗牙根对水淹环境的适生性机制,取长势一致的狗牙根分为未水淹对照组(A1)和30 cm沉水处理组(A2),A2水淹15 d后两组同时采样,提取样本总RNA作转录组测序。A1和A2测序数据经de novo组装分别获得128031和83363条高质量Unigene;A1和A2对比发现28844条差异表达基因(differentially expressed genes, DEGs),其中11858条DEGs上调表达,16986条DEGs下调表达;功能注释显示,这些DEGs主要集中在转录、翻译、碳水化合物代谢和环境适应等途径;信号通路富集显示,包括植物对病原体的防御、物质代谢、光合作用、形态发育和抗氧化等过程的103个信号通路与狗牙根对水淹生境的适生性有关;随机挑选4个DEGs作qRT-PCR分析,荧光定量结果与测序数据基本一致,说明基于转录组分析DEGs的表达情况较为可靠。该工作或可为进一步挖掘与狗牙根水淹适生性相关的调控基因和功能基因提供基础。     

Seasonal changes in the dietary compositions of rusa deer in Pangandaran Nature Reserve,West Java,Indonesia

Information regarding the food habits of tropical cervids is limited. We studied the food habits of rusa deer (Rusa timorensis), a tropical cervid in the Pangandaran Nature Reserve, West Java, Indonesia. The faecal composition of the rusa deer collected over a year was analysed using microscopy of plant fragments. The results showed marked seasonal changes: in the rainy season, the rusa deer mainly fed on Cynodon dactylon, a lawn-like grass, which accounted for approximately 50% of the faecal composition. During the dry season, C. dactylon in the faeces decreased to approximately 20%, while the composition of fruits increased, suggesting that food conditions for the deer were better in this season. This pattern differs from that of temperate cervids which can feed on abundant plant leaves during summer but are forced to consume low-quality foods such as bark and dead leaves during winter.     

An assessment of the importance of water stress in seasonally floodedC. dactylon on the Pongolo River floodplain in the formulation of guidelines for controlled flooding

Daily variation in water potential was measured inCynodon dactylon in seasonally flooded areas of the Pongolo river floodplain. Soil moisture declined during the dry winter season when the plants were exposed, causing them to experience increasing water stress. Fog and mist appeared to relieve stress but it is concluded that water stress is sufficient to reduce production during exposure. The results are discussed in relation to the timing of flood releases from the upstream Pongolapoort dam and it is concluded that the period of exposure is of less significance than the duration and frequency of inundation in the formulation of guidelines for flood releases from the dam.     

Alternatives to Fenamiphos for Management of Plant-Parasitic Nematodes on Bermudagrass

Plant-parasitic nematodes can be very damaging to turfgrasses. The projected cancellation of the registration for fenamiphos in the near future has generated a great deal of interest in identifying acceptable alternative nematode management tactics for use on turfgrasses. Two field experiments were conducted to evaluate the effectiveness of repeated applications of several commercially available nematicides and root biostimulants for reducing population densities of plant-parasitic nematodes and (or) promoting health of bermudagrass in nematode-infested soil. One experimental site was infested with Hoplolaimus galeatus and Trichodorus obtusus, the second with Belonolaimus longicaudatus. In both trials, none of the experimental treatments reduced population densities (P ≤ 0.1) of plant-parasitic nematodes, or consistently promoted turf visual performance or turf root production. Nematologists with responsibility to advise turf managers regarding nematode management should thoroughly investigate the validity of product claims before advising clientele in their use.     

Response of Cynodon dactylon to prolonged water deficits under saline conditions

Competition for available water resources in both arid and semi-arid locations has led to greater scrutiny of turfgrass irrigation. Irrigation management strategies, including deficit irrigation, need further investigation. The objective of this research was to determine the physiological response of bermudagrass (Cynodon dactylon (L.) Pers.) to prolonged water deficits under saline conditions. Bermudagrass was grown in large columns packed with three different soil types (sandy loam, silt loam and clay). Synthesized saline irrigation water was applied at three different salinity levels (1.5, 3.0 and 6.0 dS/m). Two previous experiments that were conducted with these columns over a 3.5 year period led to differential profile salinization in all 27 columns. At the end of this 3.5 year period, all irrigations were terminated and plant growth and water status were monitored over a 95 day dry-down period. Midday stomatal conductance, leaf water potential, canopy temperature, soil water in storage and stolon elongation were measured over the experimental period. On day 95, above ground tissue was harvested for dry weight and elemental tissue analysis. Midday stomatal conductance decreased around day 30 in all columns regardless of soil salinity. This decrease was not associated with a threshold leaf water potential, as midday leaf water potentials remained constant over a 60 day period. Stolon elongation also ceased before any deviation in the midday leaf water potential occurred. A concomitant reduction in evapo ranspiration was not associated with the measured decrease in stomatal conductance. This would suggest that bermudagrass may have regulated stomatal activity to compensate for lower conductances during periods of greater stress and/or that measured midday stomatal conductances cannot always be directly coupled to extended time evapotranspiration measurements.     

Differences in Cold Inactivation of Phosphoenolpyruvate Carboxylase among C4 Species: The Effect of pH and of Enzyme Concentration

Among various C4 plants we found a wide range in the level of inactivation of phosphoenolpyruvate carboxylase (PEPC) at low temperature (0 °C). The activity of the 2-fold diluted enzyme in crude leaf extracts after 60 min incubation (compared to zero time incubation) at pH 7.5, remained above 87 % at low temperatures for the species Setaria verticillata, Portulaca oleracea, and Saccharum officinarum, and between 11 and 17 % in the species Cynodon dactylon and Atriplex halimus. The enzyme exhibited intermediate levels of inactivation (42 to 58 %) for the species Amaranthus sp., Zea mays, Salsola kali, and Digitaria sanguinalis. The enzyme activity for S. verticillata was unaffected between pH 5.7 and 8.4 during incubation at room and low temperatures. Under similar conditions, the activity of the enzyme from C. dactylon was stable between pH 5.7 and 7.0 and decreased at pH above 7.0, but for Z. mays it was enhanced between pH 5.7 and 6.8 and decreased at pH above 7.0.     

三峡库区消落带狗牙根种群对水陆生境变化的响应

基于定位观测,研究了三峡水库消落带不同海拔区段狗牙根的种群密度、形态性状和生物量及其分配,结果表明:在3个海拔区段,狗牙根种群密度的大小为浅水位区段(海拔165 ～170 m)＞未经水淹区段(海拔＞172 m)＞深水位区段(海拔145～150m);根径和根系长度的大小为深水位区段＞浅水位区段＞未经水淹区段;种群总生物量和根、茎、叶生物量及茎生物量分配比率为浅水位区段＞未经水淹区段和深水位区段,根、叶生物量分配比率和地下/地上生物量的变化为深水位区段＞浅水位区段和未经水淹区段,浅水位区段的狗牙根种群应对水陆生境变化特有的适应策略是加速伸长生长,增加茎生物量分配;深水位区段的策略是增加分枝节间数量、分枝数量和叶生物量分配;二者共有的适应策略是加速根系生长、增加分蘖数量和地下生物量分配,为在陆地环境中的快速生长提供营养和能量储备.