Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 4

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
To understand the response patterns to soil drying and the water use properties of commonly reforested trees in the semiarid Loess Plateau region of China, a glasshouse experiment was carried out with the seedlings of four species, i.e., Robinia pseudoacacia, Armeniaca sibirica, Syringa oblata, and Quercus liaotungensis. Severe water stress induced by withholding water resulted in permanent wilting of most of the seedlings pot-cultured with sandy soil in 8–12 days. Predawn and midday leaf water potentials and gas exchange characteristics (e.g., stomatal conductance) in the seedlings did not show marked changes until the volumetric soil water content decreased to about 0.05. As the soil water content decreased further, these physiological parameters rapidly declined, approaching their minimal levels at the stage of permanent wilting. The response of each parameter to soil water content changes was fitted with a non-linear saturation curve. Though the results suggested that the general pattern of responses to soil drying was identical among the species, quantitative differences in drought tolerance and water use properties were detected. Leaf stomatal conductance in R. pseudoacacia and A. sibirica showed earlier responses to reduced predawn leaf water potentials. However, water use characteristics and specific leaf area indicated that these two species consumed more water and may not be as drought tolerant as S. oblata and Q. liaotungensis. These results may provide important information to compare the reforestation species with respect to soil drying.
Pressure–volume (P–V) curves are frequently used to analyze water relation properties of woody plants in response to transpiration-induced tissue water loss. In this study, P–V analyses were conducted on eight woody species growing in the semiarid Loess Plateau region of China during a relatively dry summer season using both the recently recommended instantaneous measurement and the traditional method with rehydration pretreatment. Generally, P–V-derived parameters in this study reflected conditions in a dry growth environment. Species-specific differences were also found among P–V parameters, suggesting each species uses different mechanisms to respond to drought. Based on the results from instantaneous measurements, a descending sequence for drought tolerance ranked by water potentials at the turgor loss point (Wtlp) was Rosa hugonis[Syringa oblata = Armeniaca sibirica[ Caragana microphylla[Pyrus betulaefolia[Acer stenolobum[Quercus liaotungensis[Robinia pseudoacacia. The first five species also showed lower levels of osmotic potential at full turgor (Wp sat) and higher symplastic osmotic solute content per dry weight, suggesting they possess advantages in osmotic adjustment. Also, this study supports previous reports noting rehydration pretreatment resulted in shifts in P–V parameters. The magnitude of the shifts varied with species and water conditions. The effect of rehydration was stronger for species with higher drought tolerance or subjected to the influence of drought. Differences in the parameters among species were mitigated as a result of rehydration. Those with a lower Wtlp or midday water potential were more deeply affected by rehydration. Application of instantaneous measurements was strongly recommended for proper analysis of P–V curves particularly in arid and semiarid areas
To acquire basic information about species’ salt tolerance prior to applying Elaeagnus oxycarpa to phytoremediate degraded saline areas, salt-induced changes in growth, photosynthesis, and osmolyte accumulation in E. oxycarpa seedlings were investigated. The responses of 120-day-old seedlings to NaCl application (0, 50, 100, 200, or 300 mM) were assessed for 30 days. Plant growth and biomass were not affected at low salinity (50 mM NaCl) and decreased linearly with an increase in salinity. However, seedlings tolerated up to 300 mM NaCl without any effect on survival and grew normally without toxic symptoms (such as yellow leaves at the base of the seedlings and new leaves burn) at 200 mM NaCl. Gas exchange was unaffected at 50 mM NaCl but was reduced at ≥100 mM NaCl. Maintenance of photosystem II (PSII) function (Fv/ Fm) at high salinity (200 mM) could support E. oxycarpa growth. Leaf and root Na⁺ concentrations increased with increasing salinity, although most Na⁺ was retained in the root system at low and moderate salinity (50 and 100 mM NaCl), whereas high concentrations of nutrients (e.g., K⁺ and Ca²⁺) were maintained in the leaves. The seedlings accumulated a set of important osmolytes in leaves under salt stress, showing a marked increase in sucrose, β-alanine betaine, proline, and glycine at 200 and 300 mM NaCl. These compounds indirectly may contribute to osmotic adjustment by maintaining high cation concentrations and osmoprotective functions when stress becomes severe. We conclude that salt tolerance in E. oxycarpa is based on maintenance of PSII function, ionic homeostasis, and accumulation of osmolytes.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.