根系盐胁迫对盐生植物和甜土植物的幼苗生长及矿质元素分布的影响

为了解盐胁迫对植物的影响, 研究了根系NaCl 胁迫在温室条件下对盐生植物榄仁(Terminalia catappa)和甜土植物枇杷(Eriobotrya japonica)幼苗生长、矿质元素和灰分含量的影响。结果表明:在根系盐胁迫下, 两种植物幼苗的叶片病斑多分布于中心区, 灰分含量增加, 幼苗的Na⁺-Cl^- 呈极显著的正相关关系, 盐胁迫对两种植物幼苗的5 种矿质元素(Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-)含量影响不大, 但它们在植物中的分布发生了变化。可见, 盐生植物和甜土植物抗盐性的区别是量上的不同, 没有质的差别。     

Changes in leaf water status associated with salinity in mature, field grown Prunus salicina

Seasonal and diurnal measurements of leaf water potential (ψ₁), relative water content (RWC) and stomatal conductance (g_s) were made in the field on 19-year old Prunus salicina (L.) cv. Santa Rosa, a deciduous fruit tree species, irrigated with 3 different concentrations of saline water over a 3 year period (1985-1987). With the exception of stage III of fruit growth, little or no treatment difference in Φ₁, leaf turgor potential (Φ_p), or RWC was noted during the day. Seasonal averages of morning (0700-0900) and afternoon (1500-1700) Φ_p did not decline with increasing salinity, indicating long-term osmotic adjustment in this species. Maintenance of leaf water status under saline conditions was in part a consequence of increased stomatal closure, with a subsequent reduction in leaf transpiration rate. However, during stage III of fruit growth, an increase in mean afternoon (1200-1700) stomatal conductance of 26-117%, independent of salinity treatment, was observed in 1985 and again in 1987. Higher conductance values during this period may be associated with rapid fruit expansion and greater assimilate demand. The observed increase in conductance resulted in greater leaf water loss and larger measured differences in midday ψ₁ between salinity treatments. This research indicates that for Prunus salicina in the field, salinity stress resulted in leaf water deficits only during the final period of fruit expansion and ripening.     

The effect of salinity on the dominance-diversity relations of experimental coastal macrophyte communities

Salinity and water regime have previously been recognised as the main environmental factors controlling the abundance of coastal submerged macrophytes in temporarily-flooded marshes in the Camargue. The effects of these environmental variables, which are considered interrelated, are tested experimentally by subjecting experimental macrophyte communities from six temporarily flooded marshes to different levels of salinity (from 0 to 6 g/1 Cl^?). Communities subjected to high salinity levels (4 and 6 g/1 Cl~) showed a decrease in species richness and in biomass of all species involved. The species that most frequently dominate these communities, Chara áspera and Zannichellia pedunculata, are tolerant of salt and dominate over the entire salinity range. Three species groups can be distinguished based on the distribution of their biomass and centre of gravity of distribution over the salinity range: (1) non-salt-tolerant species, ‘glyco-phytes’, (2) moderately salt-tolerant species and (3) very tolerant species (‘halophytes’). A species ordination based on the experiments appeared to give results close to those previously obtained from field data.     

Relation of source and sink during grain filling period in wheat and some aspects of its regulation

The effect of Mg²⁺, Na⁺, K⁺, ouabain and pH on ATPase activity of purified membrane fractions enriched in plasmalemma fragments from Hordeum vulgare L. (glycophyte) and Halocnemum strobilaceum L. (halophyte) was studied. Membrane ATPases from both plants were synergistically activated by K⁺ and Na⁺ in the presence of Mg²⁺. The maximum activity of the enzymes were observed at the ratio Na/K = 2–3. Ouabain (10^-4 M) almost completely eliminated the (Na⁺+ K⁺)-stimulated component of the ATPase activity. The Na, K, Mg-ATPase of Hordeum had a single pH optimum (pH 8), but that of the Halocnemum had two optima(pH 6 and 8). It appears that similar enzymes operate in the cells of both plants studied. The higher Na, K, Mg-ATPase activity of the halophyte compared to that of the glycophyte suggests the involvement of the enzyme in the extrusion of Na⁺ from the cytoplasm of cells of both plants.     

Diversity patterns of wet meadows along geochemical gradients in central Spain

Four measures of biodiversity (species number per site, total species number, mean similarity and mosaic diversity) and their relationships with soil chemical composition were studied in vascular plant communities in groundwater discharge ecosystems of central Spain. Species richness decreased with increasing salinity, alkalinity and halite concentration. Species richness was apparently controlled more by soil toxicity than by soil nutrient levels, although a positive correlation of Ca²⁺ with species richness was found after accounting for the effects of toxic compounds. All relationships were strictly monotonic. Six community types were identified based on their soil chemical characteristics: glycophyte, subglycophyte, tolerant, subalkalinophyte, alkalinophyte, and halocalcicole communities. Within community types, species richness showed very few significant relationships with soil characteristics. Mean species richness was lowest in the environmentally stressful communities. Total species richness was greatest in the ecotonal community type. Mean similarity, a measure of among-community diversity, and mosaic diversity, a measure of landscape complexity, differed among community types. Mean similarity was smaller (higher diversity) in species-poor community types, while mosaic diversity was greatest (greater complexity) in species-rich community types. The halocalcicole community type was richest in rare species.