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81.
Alphonsus K. BelaneFelix D. Dakora 《Field Crops Research》2011,124(3):279-287
Cowpea is a major food legume in Africa with relatively little information on N and C nutrition under field conditions in the continent. The aim of this study was to assess the relationship between leaf symbiotic N nutrition and photosynthetic carbon assimilation in cowpea genotypes grown under field conditions in the Guinea savanna of Ghana. The experiments were conducted in a randomized complete block design in Ghana, using 30 nodulated cowpea genotypes. Data collected from gas-exchange studies showed that genotypes with high photosynthetic rates expectedly exhibited greater stomatal conductance, high transpiration rates and increased water-use efficiency, leading to greater dry matter yield. In contrast, those with low photosynthetic rates revealed low stomatal conductance, low transpiration rates and low water-use efficiency. Quantification of symbiotic N in photosynthetic leaves indicated greater N2 fixation in genotypes with higher photosynthetic rates, leaf transpiration and better water-use efficiency. Furthermore, measurement of C in leaves also indicated greater accumulation in genotypes with higher symbiotic N yield and total N, clearly indicating a link between C and N metabolism in photosynthetic leaves. Additionally, measures of photosynthetic N-use efficiency showed that genotypes with high levels of C-fixed per unit leaf total N also exhibited greater C-fixed per unit leaf N-fixed. Data suggest that where symbiotic legumes derive a large proportion of their N from N2 fixation, photosynthetic C yield is much enhanced. 相似文献
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83.
首先阐述了批判地域主义思想,然后对当代历史街区改造的范例——成都宽窄巷子的历史文化进行了解读,接着从空间形态、空间界面、种植设计、景观设施及小品设计4个方面详细分析了宽窄巷子空间设计对地域历史文化及特色的表达,旨在为今后同类项目的改造在思想与方法上提供借鉴。 相似文献
84.
Biological Variability in Serum Cortisol Concentration Post‐adrenocorticotropic Hormone Stimulation in Healthy Dogs 下载免费PDF全文
85.
Non-exchangeable potassium (Knex) contributes to soil K availability and several extractants are used to access its contribution. This study evaluated sodium tetraphenylboron (NaBPh4) as a soil test of K availability in 20 soils from Northern Greece. Winter wheat (Triticum aestivum L. var. ‘Yecora’) was sown in a greenhouse pot experiment and five cropping cycles were carried out until K-depletion. Soils were analyzed with NH4OAc and NaBPh4 (1 and 5 min incubation periods). Critical levels of K ranged between 130–140 and 330–340 mg K kg?1 of soil for NH4OAc and NaBPh4 (1 min incubation period), respectively, and between 32 and 35 g K kg?1 of wheat dry matter. NaBPh4-K (1 min) related better with K concentration and uptake compared to NH4OAc for each cropping cycle (r2 = 0.45–0.83 and 0.44–0.89) and for all soils (r2 = 0.58 and 0.51). Similar results obtained in soils low in exchangeable K (r2 = 0.41 and 0.39). Correlation between NH4Oac- and NaBPh4-extractable K was weaker among soils below the critical level (r = 0.70) compared to those above (r = 0.93). Inclusion of illitic K and cation exchange capacity in a multiple linear regression between NH4OAc- and NaBPh4-extractable K showed that they significantly contributed to NaBPh4-extractable K. 相似文献
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88.
中国亚热带森林小流域植物生长驱动下矿物风化评估 总被引:1,自引:0,他引:1
Plant growth contributes to mineral weathering, but this contribution remains poorly understood. Weathering rates in an aggrading forested watershed in subtropical China were studied by means of geochemical mass balance. Rainfall, dry deposition, and streamwater were monitored from March 2007 to February 2012. Samples of vegetative components, rainfall, dry deposition, streamwater, representative soils, and parent rock were collected and determined for mass balance calculation and clarifying plant-driven weathering mechanisms stoichiometrically. Ignoring biomass, weathering rates of Ca2+, Mg2+, Na+, and Si were 25.6, 10.7, 2.8, and 51.0 kg ha-1 year-1, respectively. Taking biomass into consideration, weathering rates of Ca2+, Mg2+, and Si and the sum of weathering rates of Ca2+, Mg2+, Na+, K+, and Si were 2.6, 1.8, 1.2, and 1.5-fold higher than those ignoring biomass, respectively. This is attributed to plant-driven weathering due to the nutrient (e.g., Ca2+, Mg2+, and K+) absorption by vegetation and substantial proton production during assimilation of these nutrients, with the former acting as a pump for removing weathering products and the latter being a source of weathering agents solubilizing mineral components. The same pattern of weathering, i.e., higher rates of weathering with than without including biomass in mass balance calculation, was reported in previous studies; however, the extent to which plants drive weathering rates varied with vegetation types and climatic zones. The documented biological weathering driven by plants is expected to play a critical role in regulating nutrient cycling and material flows within the Earth’s Critical Zone. 相似文献
89.
[目的]研究和修正土壤的无限制水分区间。[方法]取土壤总水势为-0.3 MPa时的含水量或土壤机械阻力为0.85 MPa时的含水量作为 NLWR的下限,代替原有的是永久萎蔫点或土壤机械阻力为2.0 MPa时的含水量。用上限的最小值减去下限的最大值,即可计算出NLWR。[结果]与原有的 NLWR或土壤最小限制水分区间相比,修正后的 NLWR更具有现实意义。当 Db〉Db-thr时,土壤物理性质对作物产生阻碍作用,需进行土壤改良,当 Db〈〈Db-dv时.只要土壤含水量处于NLWR之内.土壤物理性质对作物生长无影响,此时NLWR可以作为农日1水分灌溉管理的依据。[结论]该研究为土壤物理质量演变规律与调控机制、土壤物理质量与作物生长发育及产量的关系、土壤水-肥-盐管理等方面的相关研究提供理论支持与科学依据. 相似文献
90.
《Communications in Soil Science and Plant Analysis》2012,43(20):2602-2613
ABSTRACTNickel (Ni) is an essential element for plants. Abundant information exists on Ni toxicity in soil–plant system but not much is available on its critical level of deficiency (CLD) in soils and plants. Five chemical extractants were evaluated to find a suitable extractant for Ni in Inceptisol. Twenty-one soils having low to high levels of Ni were used to grow barley (Hordeum vulgare L). The amount of Ni extracted was correlated with Ni concentration and uptake by barley. The diethylene triamine penta acetic acid-calcium chloride (0.005 M DTPA-CaC12) was identified as the most promising soil extractant for Ni. The CLD of Ni for 0.005 M DTPA-CaC12 in soil was 0.22 mg kg?1 whereas in barley plant it was 2.14 mg kg?1. Application of 7.5 mg kg?1 Ni in soil caused a significant increase in Ni concentration in the shoot of barley in all the soils irrespective of the initial Ni status. 相似文献