Effect of Rhizobium Symbiosis on Low-Temperature Tolerance and Antioxidant Response in Alfalfa (Medicago sativa L.).

Low temperature-induced stress is a major environmental factor limiting the growth and development of plants. Alfalfa (Medicago sativa L.) is a legume well known for its tolerance of extreme environments. In this study, we sought to experimentally investigate the role of rhizobium symbiosis in alfalfa's performance under a low-temperature stress condition. To do this, alfalfa "Ladak+" plants carrying active nodules (AN), inactive nodules (IN), or no nodules (NN) were exposed to an imposed low temperature stress and their survivorship calculated. The antioxidant defense responses, the accumulation of osmotic regulation substances, the cell membrane damage, and the expression of low temperature stress-related genes were determined in both the roots and the shoots of alfalfa plants. We found that more plants with AN survived than those with IN or NN under the same low temperature-stress condition. Greater activity of oxidation protective enzymes was observed in the AN and IN groups, conferring higher tolerance to low temperature in these plants. In addition, rhizobia nodulation also enhanced alfalfa's ability to tolerate low temperature by altering the expression of regulatory and metabolism-associated genes, which resulted in the accumulation of soluble proteins and sugars in the nodulated plants. Taken together, the findings of this study indicate that rhizobium inoculation offers a practical way to promote the persistence and growth potential of alfalfa "Ladak+" in cold areas.

Sodium-Related Adaptations to Drought: New Insights From the Xerophyte Plant Zygophyllum xanthoxylum.

Understanding the unusual physiological mechanisms that enable drought tolerance in xerophytes will be of considerable benefit because of the potential to identify novel and key genetic elements for future crop improvements. These plants are interesting because they are well-adapted for life in arid zones; Zygophyllum xanthoxylum, for example, is a typical xerophytic shrub that inhabits central Asian deserts, accumulating substantial levels of sodium (Na+) in its succulent leaves while growing in soils that contain very low levels of this ion. The physiological importance of this unusual trait to drought adaptations remains poorly understood, however. Thus, 2-week-old Z. xanthoxylum plants were treated with 50 mM NaCl (Na) for 7 days in this study in order to investigate their drought tolerance, leaf osmotic potential (Ψs) related parameters, anatomical characteristics, and transpiration traits. The results demonstrated that NaCl treatment significantly enhanced both the survivability and durability of Z. xanthoxylum plants under extreme drought conditions. The bulk of the Na+ ions encapsulated in plants was overwhelmingly allocated to leaves rather than roots or stems under drought conditions; thus, compared to the control, significantly more Na+ compared to other solutes such as K+, Ca2+, Cl-, sugars, and proline accumulated in the leaves of NaCl-treated plants and led to a marked decrease (31%) in leaf Ψs. In addition, the accumulation of Na+ ions also resulted in mesophyll cell enlargement and leaf succulence, enabling the additional storage of water; Na+ ions also reduced the rate of water loss by decreasing stomatal density and down-regulating stomatal aperture size. The results of this study demonstrate that Z. xanthoxylum has evolved a notable ability to utilize Na+ ions to lower Ψs, swell its leaves, and decrease stomatal aperture sizes, in order to enable the additional uptake and storage of water and mitigate losses. These distinctive drought adaption characteristics mean that the xerophytic plant Z. xanthoxylum presents a fascinating case study for the potential identification of important and novel genetic elements that could improve crops. This report provides insights on the eco-physiological role of sodium accumulation in xerophytes adapted to extremely arid habitats.

Depressive disorders among children in the transforming China: an epidemiological survey of prevalence, correlates, and service use.

BACKGROUND: To date, no one-phase survey of childhood depression has been performed in China that involves both urban and rural community children. The objective of this study was to determine the prevalence, correlates, and mental health service utilization of depressive disorders (DDs) in a community-based sample of 6-14-year-old children in south-central China. METHODS: Children (3,582) were approached through multistage sampling and interviewed using a Chinese version of the Mini International Neuropsychiatric Interview for Children and Adolescents 5.0, which is a structured interview that is administered by trained psychiatrists to obtain information from children and their guardians. RESULTS: The overall prevalence of all current DDs was found to be 2.8% (95%CI: 1.5-3.9). The risk factors for depression included being 9-14-year old, not attending school, having unmarried parents, living in a non-nuclear family (single parent or parentless family), being taken care of by people other than two parents (single parent, grandparent(s), other relatives, or others) during the past year, and not being breastfed prior to 1 year of age. Only 5.8% of the depressed children had received professional help prior to the interview. CONCLUSIONS: The prevalence of DDs among children in this part of China is relatively high compared with most figures reported in other countries. Depression in this age group has been a major public health concern, but it is often underrecognized. There is an urgent need to develop efficacious interventions aimed at the prevention and early recognition of childhood depression.

[Distribution responses of Lespedeza davurica community on Loess Plateau to climate change].

Field survey and position monitoring were conducted from 2000 to 2009 to study the effects of climate change on the distribution and growth of Lespedeza davurica community on Loess Plateau. As affected by air temperature, the appropriate growth region of L. davurica community on the Plateau had an obvious zonal distribution from northwest to southeast. For the distribution of L. davurica community, the suitable air temperature was 7.4 degrees C-10 degrees C, average population density was 13.9 plants x m(-2), and reproductive branch was averagely 11.4 per cluster. As affected by precipitation gradient, the horizontal distribution of L. davurica community changed from a constructive or predominant species in typical grassland region into a companion species in forest steppe region, and then, the community gradually became dominant species. The L. davurica community appeared as an occasional species on the half sunny slope of gullies and valleys and the sand dunes in desert steppe region, and extended gradually from its optimal region with yearly precipitation 300 -500 mm to the region with yearly precipitation 270-600 mm. Also, the L. davurica community extended from its optimal altitude 1100-1700 m to 600-1950 m. Under the background of global climate change, the eco-breadth of L. davurica community expanded gradually.