Cadmium and copper uptake and translocation in five willow (Salix L.) species

The efficacy for phytoremediation of five willow species was tested by experimental copper and cadmium uptake in a greenhouse hydroponic system. Five treatments included two concentrations (5 and 25 microM for each metal) and a control. Metal concentrations in solution as well as solution uptake were monitored. Metal resistance was assessed through effects on the dry weight of roots and shoots. The willow species tested were generally resistant of increased Cu and Cd content. Metal accumulation was found in all plant organs of all species. Growth and transpiration were not decreased by 5 microM of copper and 25 microM of cadmium in the solution for most species. 25 microM copper caused injury and reduced the dry weight for all species after 21 d. Salix nigra was highly resistant of both Cu and Cd and accumulated more metals than other species. Future field study should be conducted to confirm the findings and feasibility of the phytoremediation technology using those species.     

水溶肥对促成盆栽伊藤牡丹‘巴茨拉’开花品质的影响北大核心CSCD

伊藤牡丹‘巴茨拉’是适合反季节盆花生产的优良品种。为探讨春节异地牡丹促成栽培中水溶肥调控盆栽‘巴茨拉’开花效果,在茎伸长初期用0、0.8、1.2和1.6 g·L^(-1)均衡型水溶肥(N-P-K=20-20-20+TE)进行灌根处理,观察测定水溶肥对植株生长发育、开花质量及相关生理生化指标的影响。结果表明:(1)水溶肥灌根能显著促进盆栽‘巴茨拉’各部器官的生长和养分积累。(2)随水溶肥浓度的增加,叶片叶绿素、可溶性蛋白质和可溶性糖含量以及花枝长度、粗度和花蕾直径随之增大,各器官中氮素和钾素营养水平亦呈现增加趋势;中高浓度(1.2 g·L^(-1)和1.6 g·L^(-1))水溶肥条件下,花蕾直径分别比对照显著增大了4.4%和7.7%(P<0.05),使花促成栽培时间缩短了4.45 d和2.65 d,最佳观赏期延长了5.08 d和1.70 d。(3)中浓度水溶肥处理盛开期花朵最大,花朵直径和单株成花率分别比对照提高了16.0%和13.5%(P<0.05),并显著提高了花瓣中类黄酮、类胡萝卜素含量及色彩黄度(P<0.05)。研究发现,适宜浓度的水溶肥能够显著提高‘巴茨拉’促成栽培过程中枝叶花的协调性,使用水溶肥应成为‘巴茨拉’盆花生产的基础管理措施;反季节栽培伊藤牡丹‘巴茨拉’建议使用1.2 g·L^(-1)均衡型水溶肥进行灌根。     

Environmental forcing, invasion and control of ecological and epidemiological systems

Destabilising a biological system through periodic or stochastic forcing can lead to significant changes in system behaviour. Forcing can bring about coexistence when previously there was exclusion; it can excite massive system response through resonance, it can offset the negative effect of apparent competition and it can change the conditions under which the system can be invaded. Our main focus is on the invasion properties of continuous time models under periodic forcing. We show that invasion is highly sensitive to the strength, period, phase, shape and configuration of the forcing components. This complexity can be of great advantage if some of the forcing components are anthropogenic in origin. They can be turned into instruments of control to achieve specific objectives in ecology and disease management, for example. Culling, vaccination and resource regulation are considered. A general analysis is presented, based on the leading Lyapunov exponent criterion for invasion. For unstructured invaders, a formula for this exponent can typically be written down from the model equations. Whether forcing hinders or encourages invasion depends on two factors: the covariances between invader parameters and resident populations and the shifts in average resident population levels brought about by the forcing. The invasion dynamics of a structured invader are much more complicated but an analytic solution can be obtained in quadratic approximation for moderate forcing strength. The general theory is illustrated by a range of models drawn from ecology and epidemiology. The relationship between periodic and stochastic forcing is also considered.     

The role of amino acid metabolism during abiotic stress release

Plant responses to abiotic stress include various modifications in amino acid metabolism. By using a hydroponic culture system, we systematically investigate modification in amino acid profiles and the proteome of Arabidopsis thaliana leaves during initial recovery from low water potential or high salinity. Both treatments elicited oxidative stress leading to a biphasic stress response during recovery. Degradation of highly abundant proteins such as subunits of photosystems and ribosomes contributed to an accumulation of free amino acids. Catabolic pathways for several low abundant amino acids were induced indicating their usage as an alternative respiratory substrate to compensate for the decreased photosynthesis. Our results demonstrate that rapid detoxification of potentially detrimental amino acids such as Lys is a priority during the initial stress recovery period. The content of Pro, which acts as a compatible osmolyte during stress, was adjusted by balancing its synthesis and catabolism both of which were induced both during and after stress treatments. The production of amino acid derived secondary metabolites was up‐regulated specifically during the recovery period, and our dataset also indicates increased synthesis rates of the precursor amino acids. Overall, our results support a tight relationship between amino acid metabolism and stress responses.     

Whale killers: Prevalence and ecological implications of killer whale predation on humpback whale calves off Western Australia

Reports of killer whales (Orcinus orca) preying on large whales have been relatively rare, and the ecological significance of these attacks is controversial. Here we report on numerous observations of killer whales preying on neonate humpback whales (Megaptera novaeangliae) off Western Australia (WA) based on reports we compiled and our own observations. Attacking killer whales included at least 19 individuals from three stable social groupings in a highly connected local population; 22 separate attacks with known outcomes resulted in at least 14 (64%) kills of humpback calves. We satellite‐tagged an adult female killer whale and followed her group on the water for 20.3 h over six separate days. During that time, they attacked eight humpback calves, and from the seven known outcomes, at least three calves (43%) were killed. Overall, our observations suggest that humpback calves are a predictable, plentiful, and readily taken prey source for killer whales and scavenging sharks off WA for at least 5 mo/yr. Humpback “escorts” vigorously assisted mothers in protecting their calves from attacking killer whales (and a white shark, Carcharodon carcharias). This expands the purported role of escorts in humpback whale social interactions, although it is not clear how this behavior is adaptive for the escorts.     

Study of the incorporation of selenium into peroxidase isozyme of wheat seedling

The effects of selenium on the activity of peroxidase (POD) of wheat seedling and its isozyme pattern were studied using a greenhouse hydroponic experiment. The results show that the activity of POD is increased in response to higher Se concentration (approx 5.0 mg/L) in culture medium. The electrophoretic pattern of the POD isozyme was altered by growth of the wheat in a selenium medium. Se could incorporate into some POD isozymes during either seed germination or the seedling growth period. There is a dose-responsive incorporation of selenium in isozyme of POD and selenium content in the isozyme increase along with the increase of selenium concentration in the medium.     

NaCl stress causes changes in photosynthetic pigments,proteins, and other metabolic components in the leaves of a true mangrove,<Emphasis Type="Italic">Bruguiera parviflora</Emphasis>, in hydroponic cultures

We studied salt stress-induced biochemical changes in young, hydroponically grown plants of mangrove,Bruguiera parviflora (Rhizophoraceae). Our focus was on the effect of NaCI (applied at 100, 200, 400, or 500 mM) on leaf pigments, total soluble proteins, total free amino acids, carbohydrates, polyphenols, and proline. The total Chi content increased for 14 d after treatment with 100 mM NaCI, then gradually stabilized. At 400 mM, the total Chi content slowly decreased over the 45-d test period. However, the Chia:b ratio remained unchanged in isolated chloroplasts and in leaf tissue. Percent changes in the carotenoids content followed the same trend as for Chi, except for a 1.5-fold decrease during the 400-mM NaCI treatment, compared with the control. The total sugar content increased by 2.5-fold by Day 45 after treatment with 400 mM NaCI, whereas the starch content measured in the same treatment decreased by 40 to 45%. Leaf protein content decreased as salinity increased, which suggests either a possible disruption in the protein synthesis mechanism or, more likely, an increase in proteolytic activity. The total amino-acid pool increased steadily, by four-fold, in the 45-d, 400-mM treatment Both proline and polyphenols accumulated with increasing levels of salinity, which confirms the role of proline as a stress-induced protective metabolite in the adaptive process of this species. Our results showed that a true mangrove such as 8.parviflora can easily be sustained and propagated under low-salinity conditions. At high levels of salinity (~400 mM, beyond which they could not survive), the plants became adapted to salt stress after two to three weeks. During this adaptive period, changes in pigment and protein levels also occurred. The accumulation of proline and polyphenols played a key role in the plant’s stressinduced adjustment to NaCI under hydroponic culture conditions.     

若干北方落叶树木叶片养分的内外迁移Ⅰ.浓度和含量的变化

研究了北方12个落叶树种单位面积叶干重、叶片灰分、有机物质和7个元素的浓度和含量在落叶前后的变化,同一元素不同树种间及同一树种不同元素间有着不同的变化模式.单位面积叶干重、叶片有机物质浓度和含量在落叶后均表现下降的趋势;所有树种叶片灰分浓度和大部分树种的灰分含量(除刺槐、胡颓子、核桃楸外)均有增加;落叶时N、P、K的单位叶面积含量均可减少约1/3～2/3;Mg含量的减少在胡颓子、核桃楸、春榆、蒙古栎、日本落叶松等5个树种中发生,其余树种表现增加;落叶中Fe含量除胡颓子下降外,其余均表现升高;落叶中Ca、Si浓度和含量在所有分析树种中均表现增加趋势.     

水培条件下四种植物对Cd、Pb富集特征

利用水培方法测定了不同浓度下向日葵、蓖麻、紫花苜蓿及芥菜的生物量和植物体内重金属Cd、Pb含量,分析了植物对重金属的富集特征。结果表明:经过5周培养后,4种植物根部与地上部对重金属的富集量随着浓度的增加而增加,Cd浓度为20mg·L-1时,向日葵的根部Cd含量最高,达到237.86mg·kg-1,地上部Cd含量为89.48mg·kg-1;而Pb浓度为200mg·L-1时,芥菜根部对Pb的吸收量较高,达到597.22mg·kg-1,地上部Pb含量最高的则出现在向日葵处理Pb100mg·L-1中,为318.33mg·kg-1。4种植物对Cd、Pb的富集系数随重金属浓度的增加而减小;根部及地上部富集系数与生物量和重金属浓度呈现出一定的相关性;另外,在Cd、Pb复合处理中,一种重金属的存在会在不同程度上影响植物对另一种重金属的吸收。通过比较4种植物根部与地上部的生物量和对Cd、Pb富集特征,认为相对于其他3种植物向日葵对Cd、Pb具有较强的吸收潜力,并可以作为Cd、Pb污染土壤植物修复的备选植物。