不同播期对紫花苜蓿生长性状及越冬性的影响研究

采用随机试验设计方法,在宁南旱作农业区进行了不同播期对紫花苜蓿出苗率、生长发育、越冬率和产草量影响的研究。结果表明,在宁南地区人工种植紫花苜蓿的出苗率与播期温度存在极显著正相关关系,而不同播期土壤耕层含水量变化率较小,且基本能满足苜蓿萌发与生长的需要;播期越早,根颈越粗,入土越深,但4月份前播种,出苗率低,群体小且易形成“小老苗”;7月份以后播种。由于生长期短,植株根颈细嫩,越冬率很低或完全冻死。综合不同播期出苗率、产草量和越冬率等因素,认为在宁南地区紫花苜蓿的适宜播种期应在4月30日～6月30日。     

MULE DEER SURVIVAL AMONG ADJACENT POPULATIONS IN SOUTHWEST IDAHO

Abstract: We investigated survival and cause-specific mortality of mule deer (Odocoileus hemionus) on 3 distinct winter ranges in southwest Idaho from 1992 to 1997 to identify demographic variation and potential limiting factors based on a sample of 447 radiocollared deer. During winters 1995–1996 and 1996–1997, we modeled overwinter fawn mortality based on early winter mass, sex, activity, and habitat use variables. Annual survival rates of adult mule deer varied among the 3 adjacent study areas (χ₂² = 10.93, P = 0.004). Overwinter deer survival also varied among study areas (χ₂² = 8.00, P = 0.018), and the study area X year, study area X sex, and study area X age interactions were all significant (P ≤ 0.018). Overwinter survival differences among the study areas were not consistent over time or among sexes and ages of deer. Winter malnutrition was the main cause of mortality for both adults and fawns during the severe winter of 1992–1993, when overall survival was low. Excluding harvest, predation was the major proximate cause of deer mortality during 1993–97 when overall survival was higher. The probability of winter fawn mortality increased with lower mass (χ₂¹ = 7.38, P = 0.007), being male (χ₂¹ = 5.61, P = 0.018), smaller group sizes (χ₂¹ = 3.62, P = 0.057), and using steeper slopes (χ₂¹ = 3.05, P = 0.081). Smaller group sizes and use of steep slopes corresponded to conditions where predators were more successful. Our findings suggest that coyote (Canis latrans) predation was largely compensatory whereas mountain lion (Puma concolor) predation was apparently independent of animal condition and dependent more on deer habitat use. Early winter fawn mass was a better predictor of overwinter fawn survival than a suite of winter resource use variables, lending further support for use of fawn mass to predict winters where fawn mortality may be high. No single population in this study could be used to make reliable inferences regarding deer survival in the other populations. Survival rate measurements should be used cautiously to make inferences in populations where survival has not been directly measured.     

Loss of decreased-rubisco phenotype between generations of wheat transformed with antisense and sense rbcS

The elite UK winter wheat cv. Riband was transformed with constructs containing rbcS in sense and antisense orientations driven by the maize ubiquitin promoter with a transformation efficiency of 1.2%. Of 77 primary transformants 31% of the sense-rbcS transformed lines and 78% of the antisense-rbcS transformed lines had decreased rubisco content compared to wild-type and marker-only controls, with decreases of up to 60%. However, in the T1 progeny which inherited the transgene, only 5% showed significantly decreased rubisco content and these effects were on the margins of significance. Five potential T2 homozygous lines from T1 parents which had transgene segregation consistent with a single locus were identified. There was no significant decrease in rubisco content relative to wild-type in any of these lines (LSD of 8% for P= 0.05). Expression of antisense rbcS transgenes in two of these T2 lines was low but was increased following exposure of the plants to 37°C for 48 h. However this did not induce a significant decrease in rubisco protein content relative to controls. Southern analysis of two antisense lines showed that they had low copy number and 1–2 insertion events. In one of the two lines there was increased methylation of the ubiquitin intron in T2 samples compared to the TO primary transformant. Further work is required to establish whether methylation occurred in all the lines which lost the phenotype, and therefore the likelihood of this being the cause. The disappearance of the decreased rubisco-content phenotype between generations may therefore be attributable to (1) greater activity of the ubiquitin promoter due to greater stress in the T0 generation plants and/or (2) increased methylation of the transgene promoter region between generations.     

Fattening strategies of wintering great tits support the optimal body mass hypothesis under conditions of extremely low ambient temperature

1.  In a seasonal environment, subcutaneous energy reserves of resident animals often increase in winter and decline again in summer reflecting gradual seasonal changes in their fattening strategies. We studied changes in body reserves of wintering great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their body mass even under extreme environmental conditions.
2.  We predicted that dominant individuals will carry a lesser amount of body reserves than subordinate great tits under mild conditions and that the body reserves of the same dominant individuals will increase and exceed the amount of reserves of subordinates under conditions of extremely low ambient temperatures, when ambient temperature dropped down to −37 °C.
3.  The results confirmed the predictions showing that dominant great tits responded to the rising risk of starvation under low temperatures by increasing their body reserves and this was done at the expense of their safety.
4.  Removal experiments revealed that lower body reserves of subordinate flock members are due to the increased intraspecific competition for food under low ambient temperatures.
5.  Our results also showed that fattening strategies of great tits may change much quicker than previously considered, reflecting an adaptive role of winter fattening which is sensitive to changes in ambient temperatures.     

Zucchini Yellow Fleck Virus is an Emergent Virus on Melon in Sicily (Italy)

Since 2006, winter melon plants (Cucumis melo L. var inodorus) showing symptoms of pin‐point yellow spots were noticed in Sicily (Italy). Leaf samples were tested by enzyme‐linked immunosorbent assay to the most important viruses‐infecting cucurbits. Zucchini yellow fleck virus (ZYFV, genus Potyvirus) was the only virus detected. Surveys in 2007 and 2008 revealed an increasing number of sites in Sicily with ZYFV‐infected winter melon plants. To confirm the identity of the virus as ZYFV, two isolates from different locations were sequenced and shown to be approximately 85% identical to the published sequences of isolates previously identified in Italy and France. This is the first report of ZYFV occurring on melon in Italy.     

Influence of temperature on root development and phosphate influx in winter wheat grown at different P levels

Root development was studied in winter wheat ( Triticum aestivum L. cv Starke II) grown at 5,10, 15 and 20°C in nutrient solutions with phosphate concentrations of 10, 100 or 1000 μM . The plants were grown for 38 days (5 and 10°C), 19 days (15°C) or 14 days (20°C). At the end of the cultivation period the phosphate influx in the roots was determined with ³²P-phosphate. Root development (lateral and seminal roof length and number) was monitored throughout the cultivation period on the same individuals by repeated (approximately every second day) photocopying of the roots for measurements with digitizer and appropriate software. The 5°C treatment yielded no laterals, and the seminals were only slightly affected by the different phosphate treatments. The 10 μM phosphate treatment gave high root:shoot dry weight ratio, high average lateral root length and high specific root length [m root (g root fresh weight)^-1]. The 1000 μM phosphate treatment yielded the highest number of laterals per m seminal root, and usually also the highest absolute numbers. Phosphate influx decreased with increased P status of the roots. It is argued that phosphate influx is dependent on factors such as P status, root geometry and relative root extension rate.     

高温胁迫对华北地区冬小麦灌浆及产量的影响

冬小麦灌浆期高温是制约我国北方冬小麦产量的一个重要气候因素,随着全球气候变暖,日趋频繁的极端温度事件可能引起该地区冬小麦产量的大幅波动。为了明确冬小麦灌浆期异常高温对冬小麦产量的影响程度,在河北固城生态与农业气象试验站自然大田条件下,采用自由空气红外辐射增温技术,开展了冬小麦灌浆中后期短期高温处理模拟试验。结果表明,灌浆中后期短期高温胁迫致使冬小麦灌浆速率下降及灌浆持续时间缩短从而使粒重降低,在消除了影响粒重的其它因素的作用后,短期高温处理期间的午间平均冠层气温与粒重之间存在显著的负线性相关关系。高温对冬小麦产量的威胁程度由高温强度及其持续时间两个因素决定。结合了高温强度及其持续时间综合作用的高温有效度时被证明是一个能全面反映灌浆中后期高温胁迫影响的特征量。     

Summer and Winter Marine Heatwaves Favor an Invasive Over Native Seaweeds

Marine heatwaves (MHWs) are emerging as forceful agents of ecosystem change and are increasing in frequency, duration, and intensity with climate change. During MHWs, physiological thresholds of native species may be exceeded while the performance of invasive species with warm affinities may be enhanced. As a consequence, MHWs could significantly alter an ecosystem's invasive dynamics, but such interactions are poorly understood. Following a 10-d acclimation period, we investigated the physiological resistance and resilience of an intertidal rock pool assemblage invaded by the seaweed Sargassum muticum to realistic 14-d marine heatwave scenarios (+1.5°C, +2.0°C, +3.5°C) followed by a 14-d recovery period. We conducted mesocosm experiments in both summer and winter to investigate temporal variability of MHWs. MHW treatments had clear negative impacts on native seaweeds (Fucus serratus and Chondrus crispus) while enhancing the performance of S. muticum. This pattern was consistent across season indicating that acclimation to cooler ambient temperatures results in winter MHWs having significant impacts on native species. As climate warming advances, this may ultimately lead to changes in competitive interactions and potentially exclusion of native species, while invasive species may proliferate and become more conspicuous within temperate rocky shore environments.     

Fish species found in the rocky sublittoral during winter months as revealed by the underwater application of the anaesthetic quinaldine

Using the anaesthetic quinaldine applied underwater, fish species not normally observed in the Scottish rocky sublittoral during the winter months have been recorded, and are listed.