Changing water use and adaptive strategies along rainfall gradients in Mediterranean lupins

• There is growing interest in harnessing the genetic and adaptive diversity of crop wild relatives to improve drought resilience of elite cultivars. Rainfall gradients exert strong selection pressure on both natural and agricultural ecosystems. Understanding plant responses to these facilitates crop improvement.
• Wild and domesticated narrow‐leafed lupin (NLL) collected along Mediterranean terminal drought stress gradients was evaluated under contrasting reproductive phase water supply in controlled field, glasshouse and cabinet studies. Plant phenology, growth and productivity, water use and stress responses were measured over time.
• There is an integrated suite of adaptive changes along rainfall gradients in NLL. Low rainfall ecotypes flower earlier, accumulate lower seed numbers, biomass and leaf area, and have larger root:shoot ratios than high rainfall ecotypes. Water‐use is lower and stress onset slower in low compared to high rainfall ecotypes. Water‐use rates and ecotypic differences in stress response (Ψleaf decline, leaf loss) are lower in NLL than yellow lupin (YL). To mitigate the effects of profligate water use, high rainfall YL ecotypes maintain higher leaf water content over declining leaf water potential than low rainfall ecotypes. There is no evidence for such specific adaptation in NLL.
• The data suggests that appropriate phenology is the key adaptive trait to rainfall gradients in NLL because of the flow‐on effects on biomass production, fitness, transpiration and stress onset, and the lack of physiological adaptations as in YL. Accordingly, it is essential to match phenology with target environment in order to minimize risk and maximize yield potential.

     

Oral water ingestion in the pulmonate freshwater snail,Lymnaea stagnalis

InLymnaea stagnalis, oral uptake of ambient medium was studied using⁵¹Cr-ethylenediaminetetra-acetic acid. In normal snails Cr-ethylenediaminetetra-acetic acid uptake showed two components: a high uptake rate within the first hour followed by moderate uptake proportional with time. The tracer accumulated mainly in the digestive system. All animals showed initial, transient uptake. Moderate uptake proportional with time did not occur in snails in which the buccal ganglia had been extirpated, in which both the buccal ganglia had been extirpated and the oesophagus was sectioned, or in snails provided with an oesophageal fistula. These snails did not accumulate tracer in the intestinal system. This type of tracer accumulation clearly represented oral ingestion of surrounding water. The oral water ingestion rate ranged from 8 to 12 μl·h⁻¹·g⁻¹. Assuming complete absorption, this accounts for 20–30% of the urine production rate. At low external concentrations the contribution of oral water ingestion to Na⁺ balance is negligible. However, its importance will grow with increasing external concentrations and becomes a major factor at higher concentrations. The ingestion rate increased almost sixfold when starving snails were allowed to feed. It is suggested that oral water ingestion is a consequence of making bite cycles and swallowing.     

A living environment. Objectives and measures in the Swedish Government Bill on environmental policy 1990/91, pertaining to waters and the seas

Increased international cooperation to limit transboundary and global environmental problems, increased sectoral responsibility and decentralization, and improved information and statistics on the state of the environment are the main lines for the development of future environmental policy. For lakes, watercourses, and the seas the overall objective is to maintain viable, balanced populations of naturally occurring species. Pollution is not to limit the use of water for fishing, recreation, or water supply. Foreign species or organisms subjected to genetic mutation are only to be introduced with great restriction. Measures are suggested that will reduce environmental disturbances from agriculture and forestry, traffic, energy production, industry, goods, chemical products, and waste.Paper presented at Seminar on Ecosystems Approach to To Water Management (Oslo, Norway, 27–31 May 1991).     

Biodiversity assessment in ecological restoration above the timberline

Ecological restoration trials in high-alpine sites require sampling of indigenous plant populations. This problem is discussed briefly in relation to initial genetic diversity in the restoration material. The further part of the paper deals with restoration trials in the Swiss Alps and their assessment.The plots, set in machine-graded downhill ski runs, were revegetated with transplants of alpine species used in various combinations. Safe-site conditions were simulated with biodegradable wood-fibre mats. Surveys carried out in plots aged four to seven years focused on plant species inventory and age-state structure of mixed stands. The alpha diversity assessment included speices number and the associated aspects. The consistent increase in species number, the number of plant families represented, and range of life-forms was apparently independent of the restoration timing. The age-state structure of the mixed stands was characterized by a considerable increase in the range of age-state classes and, in particular, a regular appearance of younger variants. These changes clearly indicate development of self-sustaining plant communities influenced by reproduction of the transplants and extensive immigration. It is proposed that age-state structure be called delta diversity and included in a routine assessment of post-restoration status of both single plant populations and mixed stands.     

Uptake,Transport and Storage of Cardenolides in Foxglove. Cardenolide Sinks and Occurrence of Cardenolides in the Sieve Tubes of Digitalis lanata1

Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose-free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long-distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long-distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure-chamber technique was cardenolide-free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue.     

Responses of nitrogen and phosphorus resorption from leaves and branches to long-term nitrogen deposition in a Chinese fir plantation

为了解森林养分内循环对全球变化的响应, 基于长期模拟氮沉降试验, 研究了杉木(Cunninghamia lanceolata)人工林不同龄级(一年生、二年生和衰老)叶和枝的氮(N)、磷(P)养分分配及其再吸收特征, 并分析了不同模拟N沉降处理时间(7年和14年)杉木叶N、P养分再吸收差异。在12年生杉木中开展模拟N沉降试验, 以尿素(CO(NH₂)₂)为N源, 设N0、N1、N2和N3 4个处理水平, 施氮量分别为0、60、120和240 kg·hm ^-2·a ^-1, 每个处理重复3次。结果表明: (1)叶和枝在衰老过程中碳(C)、N和P含量逐渐降低, 且叶的C、N和P含量比枝高; N含量大小依次为一年生叶>二年生叶>衰老叶>一年生枝>二年生枝>衰老枝, 且N3 > N2 > N1 > N0, 而C:N则呈现相反的趋势; 衰老器官的C:N、C:P、N:P比新鲜器官高; N沉降增加了不同龄级叶和枝(除二年生叶外)的N、N:P和C:P, 但降低了P和C:N。(2)叶和枝的N、P养分再吸收率(RE_N、RE_P)随龄级的增加至衰老有规律地递减, 且RE_P > RE_N; 受长期N沉降的影响, RE_N叶(28.12%) <枝(30.00%), 而RE_P则为叶(45.82%) >枝(30.42%); 杉木叶和枝N:P与RE_N:RE_P之间存在极显著的线性相关关系。(3)随N沉降处理时间的增加, 叶RE_N呈降低态势, 各处理(N1、N2和N3)分别降低了9.85%、3.17%和11.71%; 而RE_P则明显上升, 分别增加了71.98%、42.25%和9.60%。研究结果表明: 不同器官、不同龄级的养分再吸收率随氮沉降处理的水平、处理时间而所有不同; RE_N:RE_P与N:P之间存在紧密关系。