Advances in salt tolerance

Summary Advances in and prospects for the development of salt tolerant crops are discussed. The genetic approach to the salinity problem is fairly new, but research has become quite active in a short span of time. Difficulties and opportunities are outlined. Salinity varies spatially, temporally, qualitatively, and quantitatively. In addition, the responses of plants to salt stress vary during their life cycle. Selection and breeding, including the use of wide crosses, are considered the best short-term approaches to the development of salt tolerant crops, but the new biotechnological and molecular biological techniques will make increasingly important contributions. Cooperation is called for among soil and water scientists, agronomists, plant physiologists and biochemists, cytologists, and plant geneticists, breeders, and biotechnologists. Given such cooperation and adequate support for these endeavors, the potential for increasing productivity in salt-affected areas can be realized.     

The ACTH-interrenal axis in the freshwater stickleback,Gasterosteus aculeatus form leiurus

Summary The ACTH-interrenal axis of the freshwater stickleback has been examined with the fish in a variety of physiological conditions. A morphometric analysis of ACTH cell ultrastructure in spring animals revealed that the only change from the winter condition was a significant decrease in the amount of perinuclear RER. The interrenal gland responded to metopirone treatment by an increase in both nuclear and cell size, although only a high dose of metopirone could degranulate the ACTH cells. Morphometry of the ACTH cells from metopirone-treated animals showed a significant increase in the amount of RER and a significant decrease in the number of free ribosomes and secretory granules, compared with control animals maintained in freshwater. Such ultrastructural changes may be expected of a cell that is stimulated to increase its secretion of polypeptide hormone. The ACTH-interrenal axis also responded to 70% seawater, as this treatment increased the interrenal cell and nuclear sizes.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.     

Comparison of the ant communities of annually inundated and terra firme forests at Trombetas in the Brazilian Amazon

Summary The composition of the ant community was assessed along standardized 100 m transects in annually flooded Varzea forest and in terra firme forests on sandy soil (Flanco forest) and on claytopped mesas (Planalto forest). Standardized samples were taken by unit-time hand collecting (day and night times), sweeping, beating, baiting and by Winkler sacks. A total of 156 species, representing 49 genera were found, of which 98, 88 and 55 were respectively found in the Planalto, Flanco and Varzea forests. Species lists are presented and the ant community composition and species richness are compared between the three forests. By considering the nesting and foraging habits of the various species, the differences in overall community composition are related to the forest type and susceptibility to inundation of the three forests which were surveyed.The data confirm the view that tropical rain forests support an extremely diverse ant fauna and comparisons with other forested areas suggest that ant species richness declines in subtropical and temperate rain forests. Although alpha diversity is high, species turnover between forests is lower than expected, suggesting that ant species richness in this forested region is not as great as is implied in some published estimates of global arthropod diversity.     

Population studies on a South African carrageenophyte: Iridaea capensis (Gigartinaceae,Rhodophyta)

An intertidal population of Iridaea capensis in the south-western Cape Province of South Africa has been studied in detail for a year. The species is generally restricted to sand-inundated rocky shores, which appears not to be the case for Iridaea species in the Pacific. In early winter (June) biomass, plant density and plant size were at a minimum. A small increase in these parameters occurred in August, but there was a massive increase in plant numbers and biomass in October. The largest plants were recorded in summer (February). The population was over 70% sporophytes in April, but switched to almost 80% gametophytes following heavy recruitment between August and October, and remained significantly gametophyte-dominated through April of the following year. Carrageenan levels were high (ca 42% of dry weight) in late winter-spring, and lowest (ca 30–35%) in summer-autumn. Strong offshore wind conditions in early summer caused a reduction in biomass, and it is hypothesized that the associated upwelling of nutrient rich water may be implicated in the lower carrageenan levels at this time.     

海水酸化及升温对刺参生长及能量收支的影响

以东亚浅海生态系统中的关键种——刺参(Apostichopus japonicus)为实验对象,研究了CO₂驱动的海水酸化及升温对其生长及能量收支的影响。实验设置对照组(大连近海水温, pCO₂ 400μatm)、升温组(大连近海水温+3℃, pCO₂ 400μatm)、酸化组(大连近海水温, pCO₂ 1100μatm)和酸化升温组(大连近海水温+3℃,pCO₂ 1100μatm)。结果表明:与对照组相比,温度升高3℃对刺参的生长无显著影响;酸化组刺参的特定生长率最低,较对照组降低0.19%/d,个体体重的变异系数最大;酸化升温组刺参的终末体重和特定生长率与对照组相较无显著差异,但其摄食率和排粪率均显著高于对照组。升温组和酸化组的刺参能量的分配模式与对照组相比未发生明显改变,但酸化升温组刺参的能量分配模式发生显著变化,其粪便能所占摄食能的比例显著升高。研究表明,海水酸化抑制了刺参的生长但未改变其能量的分配,生长的降低主要取决于摄食减少;而海水酸化与温度升高的共同作用可能会通过...     

Changes in glomerular structure after sexual maturation and seawater adaptation in males of the euryhaline teleost Gasterosteus aculeatus L.

Summary In sexually mature male sticklebacks, the renal tubular cells are transformed from ion reabsorbing to mucus secreting cells and in these fish concomitant changes take place in the glomeruli.The present study compares glomerular structure of immature males in fresh water (controls) to those of mature males in fresh water and to immature male sticklebacks in seawater. Glomerular structure is markedly altered in the latter two groups and the changes are similar to a large extent. In these two groups the renal capsules and glomeruli are smaller and the lumina of the glomerular capillaries decrease in diameter, while the number and size of the endothelial fenestrations are reduced. Mesangial cells proliferate and the mesangial matrix greatly expands in both the centrolobular region and the subendothelial space around the capillaries. The secretory activity of the podocytes is enhanced and is responsible for the observed increase in thickness of the outer layer of the basal lamina, the lamina rara externa. The area covered by the filtration slit membranes is reduced, probably as a consequence of fusion of the pedicels of the podocytes. The permeability characteristics of the glomerular filtration barrier for macromolecules, as studied with ferritin injections, remain unaltered. However, the observed differences point to a reduction of the glomerular filtration rate (GFR) during maturation in male sticklebacks, as well as during adaptation of sticklebacks to seawater. This conclusion is in line with physiological evidence.     

Fish community structure in lakeshore lagoons on long point,lake Erie,Canada

Synopsis The interaction of fluctuating water level and the Long Point topography is discussed with regard to the formation of lake-shore lagoons and their subsequent invasion by fishes. The species composition of fish communities in these lagoons was determined by 12 collections from lagoons (23 m² to 25 ha) which yielded 33 fish species. The relationship of the number of fish species to lagoon area was lognormal; that is, with increasing lagoon area the number of species rose rapidly at first but soon decreased sharply, probably limited by the number of species capable of surviving in the habitat. The marked effect of area on species number in small lagoons is considered in the context of a hypothetical seasonal pattern of occasional invasion and continuous extinction.A sequence of reproductive guilds was found. In beach lagoons psammophils and lithophils were dominant. In a large vegetated lagoon in the interior phytophils and speleophils were dominant. This sequence was paralleled by an increase in the proportion of guarding and nesting species in the communities. The sequence was disrupted in the small interior lagoons where adaptations for survival were more important than reproductive strategy.