Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the...Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the species have obvious growth ring boundaries except sometimes discontinuous in T. mongolica and Z xanthoxylum ring to semi-ring-porosity; simple perforation plate; alternate intervessel pitting; non-septate fibres; paratracheal confluent axial parenchyrna; helical thickenings and heterocellular rays. However the vessel arrangement and quantitative features of vessels were different. Vessel elements tend to be shorter and narrower and more frequent in T. mongolica than in other two species that are hardly different could lead to greater conductive safety. The variation of vessel element length and fibre length along radial direction showed irregular tendency. There was significant difference in both fibre length and vessel element length among-tree and within-tree. Furthermore, the relationships between anatomical features and adaptability to desert environments were also discussed.展开更多
Guggal, a threatened species that is endemic to western India, is tapped to extract medicinally important oleo-gum-resin （guggul）. However, the plant dies after gum exudation. The indigenous tapping techniques used ...Guggal, a threatened species that is endemic to western India, is tapped to extract medicinally important oleo-gum-resin （guggul）. However, the plant dies after gum exudation. The indigenous tapping techniques used by local people were examined in Gujarat, India to dis-cover the scientific basis behind these techniques： selection of gum in-ducer, season of tapping, and plant parts to be tapped. First, the presence of Xanthomonas axonopodis pv. commiphorae （Xac） in the gum suspen-sion used for tapping was established. This bacterium induces gum ooz-ing from the tapped plants and later, causes them to die off. The popula-tion of Xac in gum was found to decrease with the age of the gum. With that, fresh gum increased the tapping success. Second, local people pre-ferred tapping during the warm season, which we validated by determin-ing that Xac growth was best at 30 ＆#176;C. Tapping during September （mean temperature 25.7-30.0 ＆#176;C） clearly favoured growth of the pathogen and yielded maximum guggul. Multiple tapping on a mature tree ensured maximum gum extraction before its death. Finally, application of in-digenous technology under natural plant stands by the local people en-sured availability of this important raw drug for consumption. Our study established that the age-old traditional methods have a strong scientific basis. However, it is imperative to formulate strategies based on con-temporary scientific understanding to protect this natural resource before it becomes extinct.展开更多
Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in ...Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic tundra future carbon budgets.展开更多
More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters ...More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters of the sewage dump collector. The area of the lake is 8200 hectares, the maximum depth is 35 m, on average 10 - 15 m, the minimum is 3 - 5 meters. The chemical composition of lake water is chloride-sulfate and has a calcareous character. 67 species of high plants belonging to 22 families were found in this area. 17 of these species are found in the water of the lake and 50 species are found around it. Of the most common species, Phragmites communis reach a height of 4.5 - 5.5 meters. Phragmites communis make up the total area of the lake 8 - 10 hectares.展开更多
The fatty acid composition of the low water-use shrub Fremontodendron californicum was examined by high temperature capillary gas chromatography. The ground seeds were extracted by supercritical fluid extraction (SFE)...The fatty acid composition of the low water-use shrub Fremontodendron californicum was examined by high temperature capillary gas chromatography. The ground seeds were extracted by supercritical fluid extraction (SFE) to obtain the oil (25.6% w/w) and for subsequent determination of the fatty acid composition. There are five fatty acids present at 1.0% or greater with linoleic 71% of the total. Oleic, palmitic, stearic, vaccenic plus traces of palmitoleic and linolenic comprise the remainder. The fatty acid methyl ester composition would make the oil suitable for biodiesel production.展开更多
Rangeland plant community and species composition are known to be related to specific soil properties. The current study investigated the ecological influence (soil characteristics) on the selection and distribution o...Rangeland plant community and species composition are known to be related to specific soil properties. The current study investigated the ecological influence (soil characteristics) on the selection and distribution of ecological-related genotypes of dominant xerophyte species in WadiSudr of Egypt. AFLP analysis reflected the genetic profile of the samples species from two altitudinal ranges (up and midstream) and was compared statistically with the differences of their inhabiting soil characteristics on two depth levels (20 and 40 cm) using Mantel test. Correlation values (r) ranged from 0.585 - 0.778 when treating the physical and chemical properties of soil samples regardless its altitudinal area. The correlation confirms that the soil chemical and physical properties influence the selection of a certain genotypes of the dominant xerophytes plants collected from Wadi Sudr of Egypt to certain altitude, while depths at 20 and 40 cm play a key role in the early growth and then the colonization of the selected genotypes, respectively. More studies are needed to exactly test the role and the importance of each of the correlated property to the plant growth and colonization.展开更多
The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding ...The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding the sea.In this study,we investigated the vegetative succession processes related to the Aral Sea shrinkage in the Eastern Cliff of the Ustyurt Plateau in Republic of Uzbekistan,Central Asia.We compared the results of our current investigation(2010–2017)on vegetative communities with the geobotany data collected during the 1970s(1970–1980).The results showed great changes in the mesophytic plant communities and habitat aridization as a result of the drop in the underground water level,which decreased atmospheric humidity and increased the salt content of the soil caused by the shrinkage of the Aral Sea.In the vegetative communities,we observed a decrease in the Margalef index(DMg),which had a positive correlation with the poly-dominance index(I-D).The main indications of the plant communities'transformation were the loss of the weak species,the appearance of new communities with low species diversity,the stabilization of the projective cover of former resistant communities,as well as the appearance of a new competitive species,which occupy new habitats.展开更多
An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the tem...An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.展开更多
Xerophyticplants are well adapted to the semiarid conditions because they have a high potential for the use of rainwater. They can store it in their roots (xylopodiums). The Amburanacearensis, commonly called Cumaru, ...Xerophyticplants are well adapted to the semiarid conditions because they have a high potential for the use of rainwater. They can store it in their roots (xylopodiums). The Amburanacearensis, commonly called Cumaru, native of the Brazilian semiarid, is very important because of its multiple-use: good quality wood, active food ingredient, perfume and medicine production. However, its management is practically unknown. Aiming to know more about this culture, an experiment was conducted to quantify the Cumaruwater needs, evaluate its water-use efficiency and the capacity of roots to store water. Five levels of water (0%, 25%, 50%, 75% and 100% of evapotranspiration) and five-plant spacing (0.20 × 0.20 m, 0.20 × 0.10 m, 0.20 × 0.05 m, 0.10 × 0.10 m and 0.05 × 0.05 m) were tested, and the results obtained analyzed statistically throughout F test. No influence of soil water level and plant spacing in the moisture content of the whole plant, in the aerial part or in the xylopodiums was observed. However, there was an effect of the treatments on the water stored in the whole plant in the aerial part or in the roots, per unit area. More than 80% of the water was stored in the roots. The crop growing with the smaller spacing without irrigation was shown to be quite efficient in using the rainwater, compared with traditional cultures irrigated.展开更多
Two model polygons in the Central Mongolia are considered for investigation of vegetation dynamics. They are located in rainless climatic zones -- arid and semiarid. For the emphasized polygons plots of the NDVI tempo...Two model polygons in the Central Mongolia are considered for investigation of vegetation dynamics. They are located in rainless climatic zones -- arid and semiarid. For the emphasized polygons plots of the NDVI temporal variation and NDVI maps of its multi-temporal values on the base of Landsat TM imagery are constructed. The full-scale landscape indication of the selected NDVI areas with different values with the step through 0.1 is conducted. This indication is supported by the analysis of vegetation to environmental groups for drought resistance. Almost the entire territory of the emphasized polygons vegetation digression during this period was traced. The analysis of the time variation of NDVI shows a decrease of its values. This indicates a trend xerophytization already sparse vegetation of Gobi. In the semiarid climatic zone a digression vegetation trend is directly related to heavy load on the pastures.展开更多
Aims The survival and ecological distribution of plants in arid habitats are mainly conditioned by water availability and physiological adaptations to withstand drought.In the present study,we have compared the physio...Aims The survival and ecological distribution of plants in arid habitats are mainly conditioned by water availability and physiological adaptations to withstand drought.In the present study,we have compared the physiological responses to drought of two Retama raetam(retama)subspecies from Tunisia,one of them living under the desert climate(subsp.raetam)and the other one growing on the coast(subsp.bovei).Methods To physiologically characterize the two R.raetam subspecies,and to elucidate their main mechanisms underlying their tolerance to drought stress,parameters related to seed germination,growth,photosynthesis(net photosynthetic rate,intracellular CO_(2) concentration,transpiration rate,stomatal conductance and water-use efficiency)and accumulation of osmolytes(proline,glycine betaine[GB]and soluble sugars)were determined in 4-month-old plants subjected to stress for up to 1 month.Important Findings Drought significantly inhibited germination,growth and all the evaluated photosynthetic parameters.Plants of R.raetam subsp.bovei were severely affected by drought after 3 weeks of treatment when photosynthesis rates were up to 7-fold lower than in the controls.At the same time,proline and GB significantly accumulated compared with the irrigated controls,but much less than in R.raetam subsp.raetam;in the latter subspecies,proline and GB increased to levels 24-and 6-fold higher,respectively,than in the corresponding controls.In summary,the population living in the desert region exhibited stronger tolerance to drought stress than that adapted to the semiarid littoral climate,suggesting that tolerance in R.raetam is dependent on accumulation of osmolytes.展开更多
文摘Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the species have obvious growth ring boundaries except sometimes discontinuous in T. mongolica and Z xanthoxylum ring to semi-ring-porosity; simple perforation plate; alternate intervessel pitting; non-septate fibres; paratracheal confluent axial parenchyrna; helical thickenings and heterocellular rays. However the vessel arrangement and quantitative features of vessels were different. Vessel elements tend to be shorter and narrower and more frequent in T. mongolica than in other two species that are hardly different could lead to greater conductive safety. The variation of vessel element length and fibre length along radial direction showed irregular tendency. There was significant difference in both fibre length and vessel element length among-tree and within-tree. Furthermore, the relationships between anatomical features and adaptability to desert environments were also discussed.
基金financially supported by the National Medicinal Plants Board,New Delhi
文摘Guggal, a threatened species that is endemic to western India, is tapped to extract medicinally important oleo-gum-resin （guggul）. However, the plant dies after gum exudation. The indigenous tapping techniques used by local people were examined in Gujarat, India to dis-cover the scientific basis behind these techniques： selection of gum in-ducer, season of tapping, and plant parts to be tapped. First, the presence of Xanthomonas axonopodis pv. commiphorae （Xac） in the gum suspen-sion used for tapping was established. This bacterium induces gum ooz-ing from the tapped plants and later, causes them to die off. The popula-tion of Xac in gum was found to decrease with the age of the gum. With that, fresh gum increased the tapping success. Second, local people pre-ferred tapping during the warm season, which we validated by determin-ing that Xac growth was best at 30 ＆#176;C. Tapping during September （mean temperature 25.7-30.0 ＆#176;C） clearly favoured growth of the pathogen and yielded maximum guggul. Multiple tapping on a mature tree ensured maximum gum extraction before its death. Finally, application of in-digenous technology under natural plant stands by the local people en-sured availability of this important raw drug for consumption. Our study established that the age-old traditional methods have a strong scientific basis. However, it is imperative to formulate strategies based on con-temporary scientific understanding to protect this natural resource before it becomes extinct.
基金Funding for this research to PML was from the Natural Science and Engineering Research Council of Canada(NSERC)ABC was supported through the Northern Scientific Training Programan NSERC Undergraduate Student Research Award。
文摘Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic tundra future carbon budgets.
文摘More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters of the sewage dump collector. The area of the lake is 8200 hectares, the maximum depth is 35 m, on average 10 - 15 m, the minimum is 3 - 5 meters. The chemical composition of lake water is chloride-sulfate and has a calcareous character. 67 species of high plants belonging to 22 families were found in this area. 17 of these species are found in the water of the lake and 50 species are found around it. Of the most common species, Phragmites communis reach a height of 4.5 - 5.5 meters. Phragmites communis make up the total area of the lake 8 - 10 hectares.
文摘The fatty acid composition of the low water-use shrub Fremontodendron californicum was examined by high temperature capillary gas chromatography. The ground seeds were extracted by supercritical fluid extraction (SFE) to obtain the oil (25.6% w/w) and for subsequent determination of the fatty acid composition. There are five fatty acids present at 1.0% or greater with linoleic 71% of the total. Oleic, palmitic, stearic, vaccenic plus traces of palmitoleic and linolenic comprise the remainder. The fatty acid methyl ester composition would make the oil suitable for biodiesel production.
文摘Rangeland plant community and species composition are known to be related to specific soil properties. The current study investigated the ecological influence (soil characteristics) on the selection and distribution of ecological-related genotypes of dominant xerophyte species in WadiSudr of Egypt. AFLP analysis reflected the genetic profile of the samples species from two altitudinal ranges (up and midstream) and was compared statistically with the differences of their inhabiting soil characteristics on two depth levels (20 and 40 cm) using Mantel test. Correlation values (r) ranged from 0.585 - 0.778 when treating the physical and chemical properties of soil samples regardless its altitudinal area. The correlation confirms that the soil chemical and physical properties influence the selection of a certain genotypes of the dominant xerophytes plants collected from Wadi Sudr of Egypt to certain altitude, while depths at 20 and 40 cm play a key role in the early growth and then the colonization of the selected genotypes, respectively. More studies are needed to exactly test the role and the importance of each of the correlated property to the plant growth and colonization.
基金This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20020101).We also thank for the project"Modern Trends in the Development of Vegetation and Fauna of Ustyurt in the Process of Desertification"(F3MВ-2016-0910183457),which is supported by the Ministry of Innovative Development of the Republic of Uzbekistan.
文摘The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding the sea.In this study,we investigated the vegetative succession processes related to the Aral Sea shrinkage in the Eastern Cliff of the Ustyurt Plateau in Republic of Uzbekistan,Central Asia.We compared the results of our current investigation(2010–2017)on vegetative communities with the geobotany data collected during the 1970s(1970–1980).The results showed great changes in the mesophytic plant communities and habitat aridization as a result of the drop in the underground water level,which decreased atmospheric humidity and increased the salt content of the soil caused by the shrinkage of the Aral Sea.In the vegetative communities,we observed a decrease in the Margalef index(DMg),which had a positive correlation with the poly-dominance index(I-D).The main indications of the plant communities'transformation were the loss of the weak species,the appearance of new communities with low species diversity,the stabilization of the projective cover of former resistant communities,as well as the appearance of a new competitive species,which occupy new habitats.
基金supported by the National Natural Science Foundation of China (41530750, 41501108, 41371101)the CAS "Light of West China" Program
文摘An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.
文摘Xerophyticplants are well adapted to the semiarid conditions because they have a high potential for the use of rainwater. They can store it in their roots (xylopodiums). The Amburanacearensis, commonly called Cumaru, native of the Brazilian semiarid, is very important because of its multiple-use: good quality wood, active food ingredient, perfume and medicine production. However, its management is practically unknown. Aiming to know more about this culture, an experiment was conducted to quantify the Cumaruwater needs, evaluate its water-use efficiency and the capacity of roots to store water. Five levels of water (0%, 25%, 50%, 75% and 100% of evapotranspiration) and five-plant spacing (0.20 × 0.20 m, 0.20 × 0.10 m, 0.20 × 0.05 m, 0.10 × 0.10 m and 0.05 × 0.05 m) were tested, and the results obtained analyzed statistically throughout F test. No influence of soil water level and plant spacing in the moisture content of the whole plant, in the aerial part or in the xylopodiums was observed. However, there was an effect of the treatments on the water stored in the whole plant in the aerial part or in the roots, per unit area. More than 80% of the water was stored in the roots. The crop growing with the smaller spacing without irrigation was shown to be quite efficient in using the rainwater, compared with traditional cultures irrigated.
基金Russian Foundation for Basic Research(120598066r_sibir_a)
文摘Two model polygons in the Central Mongolia are considered for investigation of vegetation dynamics. They are located in rainless climatic zones -- arid and semiarid. For the emphasized polygons plots of the NDVI temporal variation and NDVI maps of its multi-temporal values on the base of Landsat TM imagery are constructed. The full-scale landscape indication of the selected NDVI areas with different values with the step through 0.1 is conducted. This indication is supported by the analysis of vegetation to environmental groups for drought resistance. Almost the entire territory of the emphasized polygons vegetation digression during this period was traced. The analysis of the time variation of NDVI shows a decrease of its values. This indicates a trend xerophytization already sparse vegetation of Gobi. In the semiarid climatic zone a digression vegetation trend is directly related to heavy load on the pastures.
基金Dhikra Zayoud's stay in Valencia was supported by a grant from the Tunisian Ministry of Higher Education and Scientific Research.
文摘Aims The survival and ecological distribution of plants in arid habitats are mainly conditioned by water availability and physiological adaptations to withstand drought.In the present study,we have compared the physiological responses to drought of two Retama raetam(retama)subspecies from Tunisia,one of them living under the desert climate(subsp.raetam)and the other one growing on the coast(subsp.bovei).Methods To physiologically characterize the two R.raetam subspecies,and to elucidate their main mechanisms underlying their tolerance to drought stress,parameters related to seed germination,growth,photosynthesis(net photosynthetic rate,intracellular CO_(2) concentration,transpiration rate,stomatal conductance and water-use efficiency)and accumulation of osmolytes(proline,glycine betaine[GB]and soluble sugars)were determined in 4-month-old plants subjected to stress for up to 1 month.Important Findings Drought significantly inhibited germination,growth and all the evaluated photosynthetic parameters.Plants of R.raetam subsp.bovei were severely affected by drought after 3 weeks of treatment when photosynthesis rates were up to 7-fold lower than in the controls.At the same time,proline and GB significantly accumulated compared with the irrigated controls,but much less than in R.raetam subsp.raetam;in the latter subspecies,proline and GB increased to levels 24-and 6-fold higher,respectively,than in the corresponding controls.In summary,the population living in the desert region exhibited stronger tolerance to drought stress than that adapted to the semiarid littoral climate,suggesting that tolerance in R.raetam is dependent on accumulation of osmolytes.
