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Objective: The main purpose of this paper was to prepare the immunoactive peptides from Meretrix meretrix Linnaeus (MLIP) by enzymatic hydrolysis, optimize the enzymolysis conditions of MLIP, and studied its immune activity. Method: MLIP was used as raw material, and five commonly used proteases were chosen to hydrolyze. The proliferation rate of RAW264.7 cells was selected as an indicator to screen the most suitable protease for enzymolysis solution. Then, the single factor test was carried out, and three factors with significant impact were selected to optimize the enzymolysis conditions by response surface method, and MLIP was prepared with the optimized process parameters. In addition, this research also studied the effects of different concentrations of MLIP on the relative proliferation rate, cell morphology and NO release of RAW264.7 cells. Results: The proliferation rate results showed that complex protease was the most suitable enzyme to prepare MLIP. The optimal enzymatic parameters obtained by response surface optimization were: pH 6.8, solid-liquid ratio 1:6.2, enzyme dosage 3 493 U/g, enzymolysis at 45 °C for 3 hours. The relative proliferation rate of RAW264.7 cells was predicted to be 71.40%, which were basically the same with the results obtained by verification experiment. In addition, RAW264.7 cells showed the best proliferation promoting effect when the concentration of MLIP was 0.4 mg/mL. All dose of MLIP caused differentiation to varying degrees of cell differentiation and had a certain promoting effect on the release of NO of RAW264.7 cells. Conclusion: The results indicated that the MLIP exhibit desirable immune activity, which might provide reference for the preparation and further study of the MLIP. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Under outdoor static simulation conditions, by measuring the relative growth rate, branch number, maximum plant height, chlorophyll a, superoxide dismutase, peroxidase and catalase of Hydrilla verticillata, Vallisneria spinulosa and Myriophyllum spicatum, we study the response of submerged plants to the changes of substrate and ammonia nitrogen conditions. The results showed that the maximum ammonia nitrogen tolerance concentrations of Hydrilla verticillata, Vallisneria spinulosa and Myriophyllum spicatum were 2. 69 mg / L, 4. 69 mg / L and 2. 69 mg / L respectively. Based on the growth rate changes of submerged plants, except that the growth rate of Hydrilla verticillata is lower than that of silt group under the condition of medium concentration of ammonia nitrogen, the submerged plants in loess group have stronger ability to adapt to ammonia nitrogen stress. The chlorophyll a content of the same plant in water with different ammonia nitrogen concentrations under different substrates showed an overall trend of increasing first and then decreasing, and there was no significant difference between different substrate groups under the same concentration. Under the same substrate environment, under the medium concentration of ammonia nitrogen, the SOD index of Hydrilla verticillata and Myriophyllum spicatum did not change significantly, while the thorn bittergrass showed a trend of rising first and then declining. In silt and loess environment, different ammonia nitrogen concentrations have no significant effect on the CAT index of Hydrilla verticillata. [ABSTRACT FROM AUTHOR]

【Background and objective】 Sensitivity of crop to drought is a measure of the response of its growth and yield to water stress occurring at different growth stages. It is a key parameter characterizing the transition from drought risk to drought loss. The objective of this paper is to experimentally investigate how drought stresses occurring at different growth stages of winter wheat affect its eventual yield. 【Method】 The experiment was conducted in a winter wheat field, and drought of different degrees was imposed at different growth stages. In each treatment, we measured the changes in total dry matter accumulation and the final yield. A sensitivity function was derived based on the growth rate of the dry matter accumulation to assess the impact of the droughts. 【Result】 ①Drought occurring at tillering stage reduced the growth rate of the total dry matter accumulation, but the reduced rate did not increase at significant level as the drought stress increased because the occurrence of the drought in this period stimulated roots to go deep to forage water in subsoil; this benefit continued to the late stage of the wheat.② Occurrence of mild drought at jointing or booting stage did not have significant effects on growth and development of the wheat, but the wheat was very sensitive to severe drought occurring at these stages. 【Conclusion】 The growth rate of the total dry matter accumulation decreased asymptotically as the drought stress occurring at tillering stage increased. Since the drought did not inhibit dry matter accumulation, insufficient irrigation can be implemented at this stage without compromising yield. The wheat was sensitive to severe drought at the jointing or booting stage, and soil water content at these stages should be kept higher than 55% of the field capacity. The wheat was very sensitive to drought at heading and flowering stage and even a mild drought could significantly hinder the crop growth; soil moisture at this stage thus hould be kept higher than 75% of the field capacity.

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shenyang Agricultural University is the property of Journal of Shenyang Agricultural University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Schima superba is a dominant species in the lower subtropical evergreen broad-leaved forest community at Dinghushan. In order to understand the construction mechanism of lower subtropical evergreen broad-leaved forest community, we have established a 20 hm2 forest biodiversity monitoring plot at Dinghushan National Nature Reserve. The data presented in this paper are based on four field investigations of all S. superba individuals from 2005 to 2017. We further analyzed the distribution characteristics of its death rate according to diameter class and habitat type. The results were as follows:(1)The number of S. superba individuals was largely reduced from 2005 to 2017.(2)Mortality rate and growth rate of S. superba showed different patterns depending on diameter class. The relative growth rate of the individuals of 1-10 cm DBH was high and rapidly decreased, while the mortality rate increased and maintained at a high level. With the increase of DBH class, the relative growth rate of the individuals of 10-50 cm DBH rose and decelerated, and then decreased, while the mortality rate decreased. The mortality rate of those individuals above 50 cm DBH was large while the growth rate was little.(3)The mortality rate of the individuals in each habitat in 2010 was not apparently different. However, in 2015, the mortality rate of individuals in high-altitude habitats(high slopes, ridges, and valleys)was greater than those in low-altitude habitats(low slopes and valleys), while those in low-altitude habitats in 2017 were higher than those in the high-altitude habitats.(4)The mortality rate was significantly positively correlated with soil pH and negatively correlated with soil organic matter, total nitrogen, total phosphorus, available potassium, and available nitrogen content. [ABSTRACT FROM AUTHOR]

Gracilaria lemaneiformis was exposed to 0, 25, 50, 100, 250 and 500 μg∙L-1 of Cu2+ to study its physiological responses to Cu2+ stress. When the Cu2+ concentration was =50 μg∙L-1, the relative growth rate (RGR) of G. lemaneiformis decreased significantly, and the optimal quantum yield (Fv/Fm), the maximum relative electron transfer rate (rETRmax), and the relative electron transfer efficiency (a) exhibited the same variation trend, compared with the control. With the increase of Cu2+ concentration, the maximum net photosynthetic rate (Pmax) and light saturation point (LSP) decreased significantly, light compensation point (LCP) had a significant increase, while chlorophyll a, carotenoid, and phycobiliprotein contents decreased after an initial increase. When the Cu2+ concentration reached 500 μg∙L-1, the chlorophyll a, carotenoid, and phycobiliprotein contents decreased significantly. It was suggested that G. leman eiformis could tolerate low concentration Cu2+ stress, but its physiological activities were inhibited markedly when exposed to =50 μg∙L-1 of Cu2+. [ABSTRACT FROM AUTHOR]