Water relations of Picea abies. I. Comparison of water relations parameters of spruce shoots examined at the end of the vegetation period and in winter

Seasonal changes of some water relations parameters of Norway spruce shoots ( Picea abies [L.] Karst.) were studied during two experiments using the pressure-volume analysis. For each experiment only shoots of a single tree were used.
During the first study, the course of the turgor loss point (as bulk osmotic pressure when turgor first reaches zero, πp) of shoots developed in late 1986 vegetation period, were measured in 1987. The turgor loss point decreased temporarily from –2.5 MPa at the beginning of the year to –3.3 MPa at the end of March, but then increased to the original level for the rest of the year.
During the second study, water relations parameters were measured in late summer 1987 and in late winter 1988. Winter shoots at full water saturation contained up to 20% less water than in late summer. Accordingly, the bulk osmotic pressure at full water saturation (π_p) decreased from –1.7 MPa in late summer to –1.9 MPa in winter, π_p decreased also from –2.2 MPa to –2.8 MPa. However, the amount of osmotically active substances (mOsmol, N) remained unchanged. The relative amount of apoplastic water in the total shoot water content appeared to drop insignificantly from 17% to 15%.
The results show that the decrease in π_o and π_p in late winter is not due to an accumulation of osmotically active substances in the vacuoles but is due to a decrease in tissue water content. The temporary reduction of the symplastic volume by deposition of osmotically inert substances seems to be the most probable cause of this phenomenon.     

Comparison of heart rate monitoring combined with indirect calorimetry and the doubly labelled water (2H218O) method for the measurement of energy expenditure in children

The aim of the present study was to compare data on 24-h energy expenditure (EE24h) in nine boys and ten girls (mean age 9.3 and 8.1 years, respectively) by heart rates (fc) combined with energy expenditure obtained from a 1-day stay in an indirect calorimeter (EEcal) and a 2-week period of normal living using the doubly labelled water method (EEdlw). Individual calibration curves were derived from fc and oxygen uptake measured during sleep (in the calorimeter), standing and walking on a treadmill. An estimation of energy expenditure based on 24-h fc monitoring (EEfc) was made during the stay in the calorimeter and on a normal school-day. Mean results showed an overestimation in EEfc compared to EEcal and EEdlw of 10.4% and 12.3% respectively, varying from 6.3% to 16.2%. These results confirmed earlier observations in adults that for a group the fc method overestimates EE24h by about 10%.     

Control of water-use efficiency by florigen

A major issue in modern agriculture is water loss through stomata during photosynthetic carbon assimilation. In water-limited ecosystems, annual plants have strategies to synchronize their growth and reproduction to the availability of water. Some species or ecotypes of flowers are early to ensure that their life cycles are completed before the onset of late season terminal drought (“drought escape”). This accelerated flowering correlates with low water-use efficiency (WUE). The molecular players and physiological mechanisms involved in this coordination are not fully understood. We analyzed WUE using gravimetry, gas exchange, and carbon isotope discrimination in florigen deficient (sft mutant), wild-type (Micro-Tom), and florigen over-expressing (SFT-ox) tomato lines. Increased florigen expression led to accelerated flowering time and reduced WUE. The low WUE of SFT-ox was driven by higher stomatal conductance and thinner leaf blades. This florigen-driven effect on WUE appears be independent of abscisic acid (ABA). Our results open a new avenue to increase WUE in crops in an ABA-independent manner. Manipulation of florigen levels could allow us to produce crops with a life cycle synchronized to water availability.     

Genetic assessment of captive Chinese water deer populations in Zhoushan Archipelago,China

Chinese water deer is a rare and vulnerable animal in China because of the poaching for medical use and the habitat loss. In this study, the genetic diversity and population genetic structure of 40 Chinese water deer from three populations in Zhoushan Archipelago were investigated with ten highly polymorphic microsatellite loci, including 4 screened from the nuclear DNA in the study, and 6 selected from the literature. According to the results, these captive populations had a higher genetic diversity than other rare cervid species, such as forest musk deer. No signs of inbreeding were detected. Low genetic differentiation among these populations was found. The probable reasons included the isolation by distance, the exchange among islands, or the supplement of the wild Chinese water deer. We proposed the deer raisers to strengthen the exchanges from different islands or mainland, and if possible, some deer would be returned to the wild to expand the wild population.     

The different effects of PEG 6000 and NaCI on leaf development are associated with differential inhibition of root water transport

The inhibitory effects of PEG on whole-plant growth can exceed the effects of other osmolytes such as NaCI, and this has been ascribed to toxic contaminants, or to reduced oxygen availability in PEG solutions. We investigated another possibility, namely that PEG has an additional inhibitory effect on root water transport which in turn affects leaf development. The effects on first-leaf growth of applications of PEG 6000 or isoosmotic NaCI to the roots were determined using hydroponically grown maize (Zea mays L.) seedlings. Leaf growth rates were inhibited within minutes of PEG application to the roots and remained inhibited for days. The inhibitory effects on growth of NaCI, and also of KCl and mannitol, were much smaller. The comparative effects of NaCI and PEG on root water transport were determined by assaying pressurized flow through excised roots. PEG induced a 7-fold greater inhibition of flow through live roots than NaCI. Killing of the roots by heat treatment, to reduce cell membrane resistances to solute penetration, nearly doubled the flow rate for roots in NaCI, but not for roots in PEG. We suggest that the greater viscosity of PEG solutions, as compared with NaCI, may be a primary factor contributing to the additional inhibition of water flow through live and killed roots. PEG did not have additional effects on leaf turgor but had a 3 times greater inhibitory effect than NaCI on the irreversible extensibility of the leaves and induced 16 times more leaf accumulation of the growth inhibitory stress hormone abscisic acid (ABA). We conclude that greater inhibition of root water transport by PEG 6000, as compared with NaCI, leads to additional reductions in extensibility, additional ABA accumulation, and a greater inhibition of leaf growth.     

模拟穿透雨减少对锐齿栎(Quercus aliena var. acuteserrata)树干液流密度的影响

降水格局变化是全球气候变化的重要特征之一,未来气候变化下,较为频繁和严峻的干旱将威胁地球中纬度部分地区的森林,但森林植被如何响应季节性干旱胁迫及其机制尚不清楚。北亚热带-暖温带过渡区分布着以锐齿栎(Quercus aliena var.acuteserrata)为优势树种的落叶阔叶林,研究其水分蒸腾代谢过程对干旱的响应是评估气候变化对过渡区天然落叶阔叶林生态系统水碳影响的关键科学问题。在典型的锐齿栎天然林中通过开展模拟穿透雨减少大型野外实验,采用Granier热扩散式探针技术监测锐齿栎树干液流密度的动态变化,研究了不同径级锐齿栎树干液流密度对模拟干旱的响应规律。结果表明:(1)穿透雨减少对树干液流密度的影响呈现季节变异。在7月份,林内穿透雨减少显著降低了锐齿栎的树干液流密度,但生长季后期的10月份林内穿透雨减少反而使锐齿栎树干液流密度显著升高。(2)不同径级的锐齿栎树干液流密度在生长季内对干旱有不同的响应,特别是小径级的树干液流密度与其他径级有较多的不同。小径级的锐齿栎树干液流密度在5、7月份表现为减雨样地显著小于对照样地,在9、10月份则表现为减雨样地显著大于对照样地。中径级的锐齿栎树干液流密度在5、10月份表现为减雨样地显著大于对照样地,在7月份则表现为减雨样地极显著小于对照样地。大径级的锐齿栎树干液流密度在6、7月份表现为减雨样地显著小于对照样地,在10月份则表现为减雨样地显著大于对照样地。     

Medicinal plants of the Argentine Yungas plants of the Las Yungas biosphere reserve, Northwest of Argentina, used in health care

We have compared the species richness of medicinal plants and the differential patterns of use amongst settlements in the Andean communities of Northwest Argentina which have differing levels of isolation. About 259 ethnoespecies, belonging to 74 plant families, were included, representing between 70 and 80% of the total estimate. The results indicate that Coronopus didymus is the most relevant and important species. The method of use of medicinal plants and the ailments treated by rural doctors compared to those of the layperson is different. Native and exotic plants are used differently according to the body system treated. There are some relationships between internal and external use and body systems and recipes. The greater medicinal species richness found in the less isolated locations is due to external enriching cultural influences.     

Molecular Identification of Aeromonas and Coliform Bacteria Isolated on m Endo Media from Lake Erie Waters

Summary Bacteria from recreational waters collected from two Lake Erie beaches in Dunkirk, New York were plated onto m Endo LES media. The 16S rRNA gene was then amplified from coliform and non-coliform bacteria using the polymerase chain reaction. The PCR products were characterized by restriction fragment length polymorphism (RFLP) analysis. A total of 8 RFLP groups were identified from the analysis of 920 samples and selected PCR products from each group were sequenced. The DNA sequence analysis indicated that more than half of the bacteria identified as coliforms on the m Endo plates belonged to the genus Aeromonas from the family Aeromonadaceae. Most of the remaining coliforms were from the Enterobacteriaceae. The data indicate that m Endo agar plates allow the growth of non-coliform bacteria, especially Aeromonas species.     

Aggregating land use quantity and intensity to link water quality in upper catchment of Miyun Reservoir

Eutrophication resulting from nutrient enrichment decreases water quality and harms ecosystem structure and function, and its degree is significantly affected by land use in the catchment. Quantifying the relationship between eutrophication and land use can help effectively manage land use to improve water quality. Previous studies principally utilized land use quantity as an indicator to link water quality parameters, but these studies lacked insight into the impact of land use intensity. Taking the upper catchment of Miyun Reservoir as a case study, we developed a method of aggregating land use quantity and intensity to build a new land use indicator and tested its explanatory power on water quality. Six nutrient concentrations from 52 sub-watersheds covering the whole catchment were used to characterize the spatial distribution of eutrophication. Based on spatial techniques, empirical conversion coefficients, remote sensing data, and socio-economic statistical data, land use intensity was measured and mapped visually. The new land use indicator was calculated and linked to nutrient concentrations by Pearson correlation coefficients. Results demonstrated that our new indicator incorporating intensity information can quantify the different nutrient-exporting abilities of different land use areas. Compared to traditional indicators that only incorporate land use quantity, most Pearson correlation coefficients between the new indicator and water nutrient concentrations increased. This new information enhanced the explanatory power of land use on water nutrient concentrations, and so will be able to help us understand the impact of land use on water quality and guide decision making for better land use management.