Physiological and transcriptional responses to heat stress in a typical phenotype of Pinellia ternata / 中国天然药物

Pinellia ternata is an important medicinal plant, and its growth and development are easily threatened by high temperature. In this study, comprehensive research on physiological, cytological and transcriptional responses to different levels of heat stress were conducted on a typical phenotype of P. ternata. First, P. ternata exhibited tolerance to the increased temperature, which was supported by normal growing leaves, as well as decreased and sustained photosynthetic parameters. Severe stress aggravated the damages, and P. ternata displayed an obvious leaf senescence phenotype, with significantly increased SOD and POD activities (46% and 213%). In addition, mesophyll cells were seriously damaged, chloroplast thylakoid was fuzzy, grana lamellae and stroma lamellae were obviously broken, and grana thylakoids were stacked, resulting in a dramatically declined photosynthetic rate (74.6%). Moreover, a total of 16 808 genes were significantly differential expressed during this process, most of which were involved in photosynthesis, transmembrane transporter activity and plastid metabolism. The number of differentially expressed transcription factors in MYB and bHLH families was the largest, indicating that these genes might participate in heat stress response in P. ternata. These findings provide insight into the response to high temperature and facilitate the standardized cultivation of P. ternata.

Physiochemical response of papaya genotypes exposed to low temperature regimes

Susceptibility to low temperature stress is the major threat to papaya cultivation. Here, we studied a low temperature stress tolerance in papaya plant. We have investigated the effect of different low temperature regimes, 28°/18°C (day/night) to 16°/06°C (day/night) with a gradual decrease of 2°C on every two days and one set with direct exposure to the low temperature of 18°/08°C (day/night), called the acclimatized plant, in five diverse papaya genotypes (Pusa Nanha, Red Lady P-7-2, P-7-9, and P-7-14) and cold tolerant wild relative of cultivated papaya genotype (Vasconcellea cundinamarcensis V.M. Badillo) under controlled regulated conditions. It was observed that there were significant variations in the physiological and biochemical parameters like photosynthetic gas exchange parameters, chlorophyll content, fluorescence parameters, relative water content (RWC), membrane stability index (MSI), total sugars content, total soluble proteins content, lipid peroxidation, and proline accumulation in leaf tissues. Maximum stomatal conductance, chlorophyll fluorescence, RWC, MSI, total sugars, total soluble proteins, proline and lowest MDA contents were observed in Vasconcellea cundinamarcensis followed by inbred P-7-9 as compared to other genotypes under low temperature stress. Among all the papaya genotypes, P-7-9 showed more adaptability to low temperature stress and it further give new insights for developing low temperature tolerant papaya genotypes, especially under changing climate situations.

Comparative physiological and histological investigations on resistant and susceptible pomegranate genotypes infected with Xanthomonas axonopodis pv. Punicae

Xanthomonas axonopodis pv. punicae (Xap) is a bacterial pathogen wreaking havoc in pomegranate cultivation. It causes bacterial blight disease dwindling yield and making fruit unfit for consumption. Physiological and histological investigations during host-pathogen interaction are prerequisite to assess the onset of defense mechanism in plants. Therefore, we tried to compare the pomegranate resistant (IC 318734) and highly susceptible (Ruby) genotypes challenged with Xap. The bacterial suspension containing Xap cells of 0.3 OD600 (~106 to 107CFU mL?1) was used for challenge inoculation. Uniformly grown resistant and highly susceptible plants were selected, the surface of leaves was pricked and spray-inoculated with bacterial suspension using native strain IIHR1 (NCBI Gen Bank ID: KT 222897). Simultaneously, the control plants were also sprayed with only distilled water and observed. A total of three replications with five plants per replication were maintained and evaluated under completely randomized design. Physiological investigations were recorded using Portable photosynthesis system (LCpro+, ADC BioScientific limited, UK) for one cycle of disease progression viz., 0, 1, 5, 10, 15 and 20 days after bacterial spray inoculation (DAI). Significant changes in gas exchange parameters were witnessed on pathogen inoculation. Higher reduction in mean percent change of photosynthetic and transpiration rate, instantaneous water use efficiency, internal CO2 content, stomatal conductance and relative water content were noticed in highly susceptible genotype than resistant one. On contrary, an increased percent mean change of intrinsic water use efficiency, carboxylation capacity and lignin was documented in resistant genotype. Relative injury caused due to bacterial infection was found high in highly susceptible genotype than resistant one. Histological investigations in highly susceptible and resistant genotype were studied on 20th day of Xap inoculation using Scanning Electron Microscopy. Highly susceptible genotype exhibited maximum deformed cells, tissues and other visible abnormalities upon Xap inoculation. Thus, this study forms a basis for effective disease management and breeding programmes in pomegranate.

QTL mapping for morphological and physiological traits in RILs of spring wheat population of WH1021 × WH711

Aim: To identify the quantitative trait loci (QTLs) associated with various morphological and physiological traits. Methodology: A recombinant inbred line (RIL) population of wheat (Triticum aestivum L.) derived from cross of heat tolerant parent WH1021 with heat sensitive parent WH711 was used. For creation of heat stress delay in sowing (four weeks) was done in late sown from timely sown. Days to heading, days to maturity, plant height along with physiological traits viz. photosynthetic rate, transpiration rate, intrinsic water use efficiency (iWUE) and normalized difference vegetative index (NDVI) were recorded in both timely and late sown conditions over two years. Results: A linkage map consisting of 22 SSR was prepared covering eleven chromosome of wheat. Using the software WinQTL cartographer version 2.5, significant genomic regions associated with heat tolerance were observed on 2A, 2D, 4A and 5A chromosomes with composite interval mapping. QTLs for photosynthetic rate were found consistently for both years on chromosome 2D. In present study, significant variation was reported for days to heading and its QTLs were identified on chromosome 2A and 2D. Interpretation: The QTLs obtained for physiological and morphological traits in wheat can be used for marker-assisted selection for heat tolerance in wheat

Photosynthetic characteristics of summer maize under different planting patterns and the responses to nitrogen application of previous crop / Características fotossintéticas do milho verão sob diferentes padrões de plantio e as respostas à aplicação de nitrogênio da cultura anterior

Maize (Zea mays L.) is one of the most important grain crops in the North China Plain. Management practices affect the photosynthetic characteristics and the production of summer maize. This two-year (2014-2015) study examined the effects of different planting patterns and the application of nitrogen to previous winter wheat (Triticum aestivum L.) on the photosynthetic characteristics, yield and radiation use efficiency (RUE) of summer maize. Field experiments used a two-factor split-plot design with three replicates at Taian, Shandong Province, China (36°09' N, 117°09' E). The experiments involved two planting patterns(ridge planting, RP; and uniform row planting, UR) and two nitrogen application levels of previous winter wheat (N1, 112.50 kg ha-1; N2, 225.00 kg ha-1). The results indicated that the application of nitrogen on previous crop and ridge planting of the following crop had significant effects on the photosynthetic characteristics and yields of summer maize. Compared with UR, this study found that RP increased the chlorophyll content index (CCI), leaf area index (LAI), net photosynthetic rate (Pn), dry matter (DM), yield and grain RUE by 4.1%, 6.3%, 5.2%, 6.4%, 8.9% and 9.4%, respectively. The CCI, LAI, Pn, yield, and grain RUE of N2 were 9.7%, 3.3%, 3.7%, 10.0% and 10.1% higher than those of N1, respectively. RP combined with the application of nitrogen on previous crop of winter wheat could increase the CCI, LAI, Pn, DM, ultimately increasing the grain yield and RUE of the following summer's maize. It was concluded that previous crop nitrogen application and RP pattern treatment resulted in optimal cropping conditions for the North China plain.

O milho (Zea mays L.) é uma das culturas de grãos mais importantes da Planície do Norte da China. Práticas de manejo afetam as características fotossintéticas e a produção do milho verão. Este estudo de dois anos (2014-2015) examinou os efeitos de diferentes padrões de plantio e a aplicação de nitrogênio ao trigo de inverno anterior (Triticum aestivum L.) sobre as características fotossintéticas, produtividade e eficiência de uso de radiação (RUE) do milho verão. Experimentos de campo usaram um delineamento em parcelas subdivididas de dois fatores com três repetições em Taian, província de Shandong, China (36°09' N, 117°09' E). Os experimentos envolveram dois padrões de plantio (ridge planting, RP; e uniform row planting, UR) e dois níveis de aplicação de nitrogênio do trigo de inverno anterior (N1, 112,50 kg ha-1; N2, 225,00 kg ha-1). Os resultados indicaram que a aplicação de nitrogênio na cultura anterior e no plantio RP da cultura seguinte teve efeitos significativos nas características fotossintéticas e na produtividade do milho verão. Comparado com o plantio UR, este estudo concluiu que RP aumentou o índice de conteúdo de clorofila (CCI), índice de área foliar (LAI), taxa fotossintética líquida (Pn), matéria seca (DM), produtividade e RUE de grãos em 4,1%, 6,4%, 5,2%, 6,4%, 8,9% e 9,4%, respectivamente. Os valores de CCI, LAI, Pn, produtividade e RUE de N2 foram 9,7%, 3,3%, 3,7%, 10,0% e 10,1% superiores aos de N1, respectivamente. RP combinada com a aplicação de nitrogênio na safra anterior de trigo de inverno poderia aumentar os valores de CCI, LAI, Pn, DM, aumentando o rendimento de grãos e RUE do milho do verão seguinte. Concluiu-se que a aplicação prévia de nitrogênio na colheita e o tratamento com padrão RP resultaram em condições ótimas de cultivo para a planície do norte da China.

Study on the Photosynthetic Characteristics of Two Cultivars Prunus Humilis Bge. in Shandong Province / 世界科学技术-中医药现代化

To study the photosynthetic physiological characteristics of Cultivars Prunus Humilis bge. in the region of shandong, analyze on the relationship between the quality of seeds and photosynthesis, In order to formulate reasonable cultivation measures and improve the yield quality of seed production. LI-6400 portable photosynthesis apparatus was used to determine light response curve, diurnal change of photosynthetic parameters of Huadong 1 and Huadong 2. Using vernier caliper and electronic balance to measure the quality data of two varieties of eucalypis, the quality difference was analyzed. Two kinds of Prunus Humilis bge, cultivating in Shandong, had higher photosynthetic rate and higher light saturation point, and the photosynthetic rate were "unimodal" type curve. The change of the two peaks all appeared at11: 00, and had no obvious "lunch break" phenomenon. The photosynthetic rate, the utilization of strong and weak light, and the efficiency of absorption and conversion of light energy of Huadong 2, were all higher than that of Huadong 1, which had better quality. The quality of seed of Prunus Humilis bge is related to its photosynthetic capacity. When planting Prunus Humilis bge., we should formulate reasonable cultivation measures according to its features such as photosynthesis, transpiration, water use efficiency.

Photosynthetic production of wheat under precision planting patterns in northern china / Produção fotossintética de trigo através de padrões de plantação de precisão no norte da china

Winter wheat (Triticum aestivum) is cultivated across a wide region; however, water is scarce during the growing season of wheat in the Northern Plain of China. Therefore, winter wheat should be irrigated to maintain a stable and high grain yield. The aim of this field study was to develop a water-conserving precision planting pattern for winter wheat that is grown in the Northern China Plain with the purpose of exploring the benefits in maintaining water and effects on wheat productivity. To accomplish this, several production variables and photosynthetic indexes were measured, including the number of stems, the leaf area index (LAI), photosynthetically available radiation (PAR), net photosynthetic rate, and grain yield. The study was carried out during the 2011­2012 and 2012­2013 winter wheat growing seasons. The experiment included a double-row planting pattern (DRPP) and a single-row planting pattern (SRPP), both of which were either irrigated or rainfed. The area of each plot was 9 m2, and the experimental design was a randomized blocks design with three replicates. All results were analyzed with an ANOVA, the F test, and the LSD (p 0.05) for means comparison. PAR capture ratios in the DRPP were higher than those in the SRPP at 50­120 cm above the ground. The photosynthetic traits of flag leaves under irrigated conditions were not significantly influenced by the respective planting pattern. However, at a growth stage of 80 under the rainfed conditions, the mean photosynthetic rate within flag leaves in the DRPP was higher than that in the SRPP. Furthermore, the DRPP under rainfed conditions was more likely to increase the apparent quantum yield (AQY) of flag leaves than the yield obtained under irrigation. These results suggest that DRPP optimizes the canopy PAR distribution in winter wheat and contributes to the maintenance of a higher photosynthetic capacity in the flag leaves under water stress (the rainfed condition). This relationship may be applied in demonstration trials to encourage winter wheat farmers to incorporate the use of DRPP in the drought-prone areas, which are subjected to insufficient precipitation during the growing stage of wheat in Northern China.

O trigo de inverno (Triticum aestivum) é cultivado em uma vasta região; no entanto, a água é escassa durante a estação de crescimento do trigo na Planície do Norte da China. Assim, o trigo de inverno deve ser irrigado para manter um rendimento de grãos estável e elevado. O objetivo deste trabalho de campo foi o de desenvolver um padrão de plantação de precisão que conserve a água para o trigo de inverno que é cultivado na Planície do Norte da China com o propósito de explorar os benefícios da retenção de água e os efeitos na produtividade do trigo. Para isso, diversas variáveis de produção e índices fotossintéticos foram medidos, incluindo o número de hastes, o índice de área da folha (do inglês, LAI - leaf area index), a radiação fotossinteticamente disponível (do inglês, PAR - photosynthetically available radiation), taxa fotossintética líquida e o rendimento de grãos. O estudo foi conduzido durante as estações de crescimento do trigo de inverno em 2011-2012 e 2012-2013. O experimento incluiu um padrão de plantação em fila dupla (do inglês, DRPP - double-row planting pattern) e um padrão de plantação em fila única (do inglês, SRPP - single-row planting pattern), em ambos os casos ou foram irrigados artificialmente ou através da chuva (regadio e sequeiro). A área de cada lote de terra foi de 9 m2, e o delineamento experimental foi um de blocos aleatórios com três repetições. Todos os resultados foram analisados com uma ANOVA, um teste F, e um LSD (p 0.05) para a comparação das médias. As taxas de captura de PAR no DRPP foram maiores do que aquelas no SRPP a 50-120 cm acima do solo. As características fotossintéticas das folhas-bandeira (do inglês, flag leaves) sob condições de irrigação artificial não foram significativamente influenciadas pelo respectivo padrão de plantação. No entanto, num estágio de crescimento de 80% abaixo das condições de irrigação pela chuva, a taxa fotossintética média dentre as folhas-bandeira no DRPP foi maior que aquela observada no SRPP. Além disso, o DRPP sob condições de irrigação pela chuva foi mais suscetível ao aumento do rendimento quântico aparente (do inglês, AQY - apparent quantum yield) das folhas-bandeira do que o rendimento obtido através da irrigação artificial. Estes resultados sugerem que o DRPP otimiza a distribuição PAR do dossel no trigo de inverno e contribui para a manutenção de uma maior capacidade fotossintética nas folhas bandeira sob estresse hídrico (a condição de sequeiro). Esta relação pode ser aplicada em ensaios de demonstração para encorajar os agricultores de trigo de inverno a incorporar o uso do DRPP em áreas propensas à seca, que estão submetidas a precipitação insuficiente durante a fase de crescimento do trigo no Norte da China.

Research on photosynthetic and eco-physiological characteristics of Epimedium pseudowushannense in different growing age / 中国中药杂志

Epimedium is a widely used medicinal plants. Due to excessive use of wild resources and resource constraints, artificial cultivation is the only way to achieve sustainable use of resources. E. pseudowushannense is intended to achieve the first cultivated species, but plant production technology is not yet fully mature.The diurnal variation of photosynthetic and eco-physiological characteristics of E. pseudowushannense in different growing age was studied by the CI-340 Portable Photosynthesis System under natural conditions. The net photosynthetic rate (Pn), stomatal conductance (C), intercellular CO2 concentration (Ci), photosynthetically active radiation (PAR), relative humidity (RH), air temperature (Ta), apparent mesophyll conductance (ALMC), transpiration rate (E), leaf temperature (Tl), water use efficiency (WUE) and other photosynthetic physiological factors and environmental factors were measured. The obtained data was analyzed by correlation analysis, path analysis and stepwise multiple-regression analysis to explore the relationship between net photosynthetic rate and physiological and ecological factors. The results show that： ①The daily variation of the Pn, E, ALMC, C of E. pseudowushannense in different growing age took on"two peak type", the Pn was with an obvious midday depression phenomenon at noon.②The Pn, ALMC and C of annuals' were significantly higher than biennial or three-year; but the Ci was basically a three-year > biennial> annual.③The correlation analysis, path analysis and stepwise regression analysis showed that ALMC, Ci, Ta might played important role in the Pn and ranked as ALMC>Ci>Ta.

Study on leaf transpiration and stomatal structure of medicinal plant Tetrastigma hemsleyanum / 中草药

Objective: Taking annual Tetrastigma hemsleyanum (Tetrastigma Radix) from three habitats, Taizhou, Minhou, and Shunchang, as materials to study the effects of different light intensity stress on the stomatal shape and leaf transpiration. Methods: The stomata, leaf transpiration rate, net photosynthetic rate, and stomal structure of T. hemsleyanum were observed using a scanning [0-2000 μmol/(m2·s)] to explore the optimal light intensity. Results: The stomata with surround and parallel distribution types were only distributed in the lower epidermis in the leaves of T. hemsleyanum; The transpiration rate, stomatal conductance, and net photosynthetic rate of T. hemsleyanum from the two habitat regions (Minhou and Taizhou) by rising after falling with the 30℃ stress, which suggested the stress could make the light intensity heavier. At the same time, the transpiration rate, stomatal conductance, and net photosynthetic rate of T. hemsleyanum from the habitat region Shunchang were rising. The stomatal type of leaves was 600 μmol/(m2·s) in Minhou, and 1900 μmol/(m2·s) in Shunchang, when the water utilization ratio of T. hemsleyanum leaves from the three habitats was higher. Conclusion: Different habitats and light intensity are the important factors of leaves transpiration in natural world, which is more beneficial to the growth of the root crops and suitable for the accumulation of flavonoids in plants.

Infectividad y efectividad de rizobios aislados de suelos de la Costa Caribe colombiana en Vigna unguiculata / Infectivity and effectiveness of isolated rhizobia from colombian Caribbean Soils in Vigna unguiculata

Es el primer estudio en Colombia que abarca una evaluación de rizobios nativos asociados a frijol Caupí (Vigna unguiculata L. Walp.) en los departamentos del Cesar y la Guajira. En esta investigación, se demostró que la utilización de aislamientos de rizobios nativos aislados a partir de nódulos, mejoraron el desarrollo del frijol Caupí (Vigna unguiculata L. Walp.), siendo estas bacterias más eficientes que los tratamientos químicos y absolutos (sin inóculo ni fertilización) y que las cepas inducidas mejorando además, la fijación biológica de nitrógeno y la tasa fotosintética. Como aportes del estudio, se determinó que en condiciones de invernadero la fertilización biológica fue más eficiente que la química y que, de acuerdo a los resultados obtenidos de las diferentes variables agronómicas evaluadas, esto podría influir positivamente en los rendimientos nutricionales del cultivo, base alimentaria de los sistemas ganaderos de estas regiones del país y fuente alimenticia de la comunidad indígena y de bajos recursos económicos.

This is the first study in Colombia which covers an evaluation of native rhizobium associated to the Caupí bean (Vigna unguiculata L. Walp.) in the departaments of Cesar and Guajira. In this research it was demonstrated that the use of native rhizobium isolated from nodes, improved the development of the Caupí bean (Vigna unguiculata L. Walp.), being this bacteria more efficient than the chemical and absolute treatments (without inoculum and fertilization) also improving the biological nitrogen fixation and the photosynthetic rate. As contribution of the study, it was determined that in greenhouse conditions and according to the results obtained from differents measured agronomic variables, this could influence positively in the nutritional performance of the crop, basis of food of the cattle system of this regions of the country and the food source of the indigenous community of low economic income.

Study on Association of Spad Chlorophyll Meter Reading (SCMR), Photosynthesis and Transpiration Rate with Grain Yield in Sorghum Genotypes Under Post Flowering Moisture Stress Conditions.

A field experiment was conducted during rabi 2012-13 at research farm of Directorate of Sorghum Research, Rajendranagar, Hyderabad. The experiment was laid out in a split plot design, replicated thrice, with 10 Sorghum genotypes as main treatment (well watered and water stress conditions) and with 10 genotypes are sub treatments CRS 4, CRS 19, CRS 20, PEC 17, CSV 18, M 35-1, Phule chitra, Phule moulee, EP 57 and CRS 1). Photosynthetic rate and stomatal resistance at 15 and 30 DAF were positively and significantly correlated with grain yield while the transpiration rate at 15 and 30 DAF exhibited negative correlation with grain yield. SPAD chlorophyll meter reading (15 and 30 DAF) and chlorophyll content at 30 DAF had positively significant correlation with grain yield.

Dynamic studies on photosynthetic characteristics and growth development of Perilla frutescens / 中草药

Objective: To provide basic theory for rational cultivation and comprehensive utilization of Perilla frutescens. Methods: The photosynthesis and growth characteristics were measured every 25 d from July 10th, 2013. Results: Logistic equation of dry matter weight was firstly established, and the slightly increasing stage was also called seedling stage (0-75 d); The flower budding stage was 76-84 d, the blooming stage was 85-95 d, and the 20 d was called period of accelerating growth stage; The period of decelerating growth was defoliation period (96-125 d). As was observed both specimens "a" and "b", chlorophyll content increased and reached the peak value during flower budding before going on a gradual decline, but not before that of soluble proteins. The Hill reaction, as well as Ca2+-ATPase and Mg2+-ATPase activities all reached the peak values just before blooming began; The photosynthesis rate was at peak twice during seedling stage, which was once more than in any other stage of the growth of Perilla frutescens. Strong positive correlation was observed between stomatal conductance and transpiration rate. Conclusion: For maximum yield of leaf, stem, or seed, harvesting should take place either before flowers bloom or after leaves fall. All growth-spurring measures should be implemented before growth rate reaches a zenith or risk not being effective.

Limnology in El Dorado: some surprising aspects of the regulation of phytoplankton productive capacity in a high-altitude Andean lake (Laguna de Guatavita, Colombia)

High-altitude mountain lakes remain understudied, mostly because of their relative inaccessibility. Laguna de Guatavita, a small, equatorial, high-altitude crater lake in the Eastern Range of the Colombian Andes, was once of high cultural importance to pre-Columban inhabitants, the original location of the legendary El Dorado. We investigated the factors regulating the primary production in Laguna de Guatavita (4°58’50” N - 73°46’43” W, alt. 2 935m.a.s.l., area: 0.11km², maximum depth: 30m), during a series of three intensive field campaigns, which were conducted over a year-long period in 2003-2004. In each, standard profiles of temperature, oxygen concentration and light intensity were determined on each of 16-18 consecutive days. Samples were collected and analysed for chlorophyll and for biologically-significant solutes in GF/F-filtered water (NH4+, NO3- , NO2-; soluble reactive phosphorus). Primary production was also determined, by oxygen generation, on each day of the campaign. Our results showed that the productive potential of the lake was typically modest (campaign averages of 45-90mg C/m².h) but that many of the regulating factors were not those anticipated intuitively. The lake is demonstrably meromictic, reminiscent of karstic dolines in higher latitudes, its stratification being maintained by solute- concentration gradients. Light penetration is poor, attributable to the turbidity owing to fine calcite and other particulates in suspension. Net primary production in the mixolimnion of Laguna de Guavita is sensitive to day-to-day variations in solar irradiance at the surface. However, deficiencies in nutrient availability, especially nitrogen, also constrain the capacity of the lake to support a phytoplankton. We deduced that Laguna de Guatavita is something of a limnological enigma, atypical of the common anticipation of a “mountain lake”. While doubtlessly not unique, comparable descriptions of similar sites elsewhere are sufficiently rare to justify the presentation of the data from Laguna de Guatavita that our studies have revealed so far.

Los factores que regulan la producción primaria en un lago remoto, pequeño, ecuatorial y de elevada altitud en la región Oriental de los Andes Colombianos (4°58’50” N - 73°46’43” W, altura 2 935m.s.n.m., área 0.11km² y profundidad máxima 30m), que también tuvo importancia cultural para los indígenas precolombinos y los orígenes de la leyenda de El Dorado, fueron investigados. La relativa lejanía del lugar requirió una serie de tres campañas intensivas de estudio, en un periodo de un año (2003-2004). Durante cada campaña se realizaron perfiles temperatura, concentración de oxígeno e intensidad de luz. Se recolectaron muestras para medir la concentración de clorofila y de solutos de significado biológico en agua filtrada GF/F. Cada día de la campaña se llevaron a cabo mediciones de la producción primaria, como se indica por la producción de oxígeno. Estas demostraron que el potencial productivo es particularmente modesto (promedio de campañas de 45-90mgC/m².h, pero casi todos los aspectos de su regulación fueron sorprendentes y contrarios al sentido común. El lago es meromíctico, reminiscencia de dolinas kársticas de latitudes más altas y la estratificación se mantiene por los solutos. La penetración de luz es pobre, atribuible a la alta turbidez debida a la calcita fina y a otras partículas en suspensión. La producción primaria neta del mixolimnion de la Laguna de Guatavita es sensible a las variaciones del día a día de la radiación superficial. Deficiencias en la disponibilidad de nutrientes, sobre todo, del nitrógeno, también limitaron la capacidad productiva del fitoplancton. La laguna de Guatavita es una especie de enigma limnológico: aunque sin duda, no es el único, las descripciones de sitios similares en otras partes son lo suficientemente raras para justificar la presentación de los datos revelados hasta hoy en nuestro estudio.

Cadmium: Toxicity and tolerance in plants.

Of all the non-essential heavy metals, cadmium (Cd) is perhaps the metal which has attracted the most attention in soil science and plant nutrition due to its potential toxicity to humans, and also its relative mobility in the soil-plant system. This review summarizes the toxic symptoms of Cd in plants (i.e. growth retardation, alterations of photosynthesis, stomatal movement, enzymatic activities, water relations, interferences with mineral uptake, protein metabolism, membrane functioning, etc.) but also includes the mechanisms of cadmium uptake, translocation and deposition. Moreover, it also throws light on chelation, including identification of Cd ligands present in cytosol and vascular tissue. Cadmium-induced oxidative stress is also considered as one of the most widely studied topics in this review.

Alterações morfofisiológicas em folhas de Coffea arabica L. cv. "Oeiras" sob influência do sombreamento por Acacia mangium Willd / Morphophysiological alterations in leaves of Coffea arabica L. cv. 'Oeiras' shaded by Acacia mangium Willd

Diferenças na disponibilidade de radiação podem causar modificações na estrutura e função das folhas do cafeeiro, que podem responder de maneira diferencial à radiação por alterações morfológicas, anatômicas, de crescimento e na taxa fotossintética. O objetivo deste trabalho foi avaliar características morfofisiológicas de cafeeiros (Coffea arabica L. cv. "Oeiras") sombreados por acácia (Acacia mangium Willd.) na época seca e chuvosa no sul de Minas Gerais. As maiores taxas fotossintéticas e maiores espessuras da epiderme adaxial foram observadas na estação chuvosa nas linhas de cafeeiros a pleno sol. O sombreamento influenciou em menor espessura das folhas e em espaços intercelulares maiores no tecido esponjoso. Foi também verificada mudança na forma dos cloroplastos, os quais apresentaram-se mais alongados em folhas de cafeeiros a pleno sol quando relacionados aos arborizados.

Light availability is one of the most important environmental factors affecting leaf structure and functions in coffee plants that can respond differently to radiation by changes in leaf anatomy, morphology, growth and photosynthetic rate. The objective of this research was evaluate some morphophysiological aspects in leaves of coffee (Coffea arabica L. cv. 'Oeiras') cropped under shelter trees in the south of Minas Gerais during the rainy and dry season. The shade caused lower leaves thickness and higher intercellular spaces in spongious tissue. There was also verified a change in chloroplast shape, which showed more elongated in coffee tree kept at full sunlight in relation to that ones maintained on shading.

Effect of Cucumber Mosaic Virus-encoded 2b Protein on Photosynthesis and Chloroplast Structure of The Host Plant / 生物化学与生物物理进展

The 2b protein encoded by Cucumber mosaic virus(CMV)plays an important pathogenicity role in many solanaceous hosts,but mechanism of inducing disease is still unknown.In order to investigate virulence of the 2b protein on Nicotiana glutinosa plants,in terms of chloroplast structure and photosynthesis,a mutant Fny-CMV?2bpro,which cannot express the 2b protein,was achieved by introducing mutant sites in the 2b gene of Fny-CMV.N.glutinosa seedlings were inoculated with wild-type Fny-CMV and the mutant Fny-CMV?2bpro,and were analyzed for symptom expression,chlorophyll content,photosynthetic rate,and ultra-structural alteration of chloroplast.Up to 30 days post inoculation,wild-type Fny-CMV caused symptoms of severe mosaic,leaf deformation,and stunting,reduced photosynthetic rate and chlorophyll content,and altered the ultra-structure and morphological characters of the chloroplasts.However,host seedlings inoculated with the mutant Fny-CMV?2bpro expressed only slight mosaic symptom.Their photosynthetic rates and chlorophyll contents were not significantly different from those of the mock-inoculated plants,and the ultra-structure and morphological characters of their chloroplasts appeared to be normal.The observed low photosynthetic rates and chlorophyll contents were related to the breakage of the chloroplast morphology and ultra-structure.Results of Northern blotting showed that the virulence of 2b protein was associated with high accumulation level of CMV progeny RNAs in systemic leaves.Non-expression of the 2b protein reduced the accumulation levels of its genomic RNAs 1 and 2.The level of subgenomic RNA4,encoding CP protein,was found to be significantly decreased.

Characteristics of photosynthesis in three Dendrobium species / 中草药

Object To determine the diumal changes of photosynthesis, its relationships with light intensities and temperatures, and the contents of chloroophyll in leaves of Dendrobium candidum Wall. ex. Lindl., D. wilsonii Rolfe and D. hercoglossum Reichb. f. Methods The net photosynthetic rate (NPR) was measured at intervals of 1.5 h during daytimes 7:30—16:30, under the photosynthetic affective rates 0—140 mmol/(m 2?s), and under the temperatures 29.6—38.2 ℃; contents of chlorophyll a and b in leaves were measured. Results NPR, light saturation point and compensation point were low in each of the three Dendrobium L. species. The NPR peaked during 8:00 and 10:00 am, and thereafter decreased rapidly as the temperature and light intensity increased. Content of chlorophyll b was high in the leaves. Conclusion These results indicated that the Dendrobium L. species, which are sciophyte plants, have great adaptations to their growing habitats.