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11.
Nitrogen nutrition and water stress effects on leaf photosynthetic gas exchange and water use efficiency in winter wheat 总被引:7,自引:0,他引:7
The responses of gas exchange and water use efficiency to nitrogen nutrition for winter wheat were investigated under well-watered and drought conditions. The photosynthetic gas exchange parameters of winter wheat are remarkably improved by water and nitrogen nutrition and the regulative capability of nitrogen nutrition is influenced by water status. The effects of nitrogen nutrition on photosynthetic characteristics and on the limited factors to photosynthesis are not identical under different water status. Intrinsic water use efficiency (WUE(i)) of the plants at the high-N nutrition was decreased by a larger value than that of the plants in the low-N treatment due to a larger decrease in photosynthetic rate than in transpiration rate. Carbon isotope composition of plant material (delta(p)) is increased by the increase of drought intensity. The delta(p) at a given level of C(i)/C(a) is reduced by nitrogen deficiency. Leaf carbon isotope discrimination (Delta) is increased by the increase of nitrogen nutrition and decreased by the increase of drought intensity. Transpirational water use efficiency (WUE(t)) is negatively correlated with Delta in both nitrogen supply treatments and increased with the nitrogen supply. 相似文献
12.
The revegetation of abandoned farmland significantly influences soil organic C (SOC) and total N (TN). However, the dynamics of both soil OC and N storage following the abandonment of farmland are not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0–5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr), and higher in older grasslands (30 yr). Soil OC and N storage (0–100 cm) was significantly lower in the younger grasslands (<20 yr), had increased in the older grasslands (30 yr), and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0–30 cm) soil levels. 相似文献
13.
Foliar δ<Superscript>13</Superscript>C values of nine dominant species in the Loess Plateau of China
The foliar stable carbon isotope compositions (δ13C) of nine dominant species in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi, and Shenmu, standing from
the south to the north in the Loess Plateau of China were studied. The results showed that foliar δ13C values ranged from −22.61 to −30.73 ‰ with an average of −27.23 ‰ in 141 C3 plant samples collected from the Loess Plateau. Foliar δ13C values varied significantly (p<0.001) among the nine C3 species, which were Pinus tabulaeformis Carr., Robinia pseudoacacia L., Zizyphus jujuba Mill. var. spinosus Hu., Rubus parvifolius L., Hippophae rhamnoides L., Caragana korshinskii Kom., Lespedeza davurica (Laxm.) Schindl., Artemisia sacrorum Ledeb. var. incana Mattf., and Agropyron cristatum Gaertn. Comparatively, R. pseudoacacia, H. rhamnoides, and C. korshinskii had much higher δ13C values than the other six species, while A. sacrorum had the lowest δ13C value. There was no significant difference in foliar δ13C value among five species, P. tabulaeformis, Z. jujuba, R. parvifolius, L. davurica, and A. cristatum. Considering the life forms categorized from nine C3 species, trees and shrubs had significantly higher δ13C values than herbs (p<0.001). The deciduous tree R. pseudoacacia had much higher δ13C value than the evergreen tree P. tabulaeformis (p<0.01). Among the four shrubs, foliar δ13C values in H. rhamnoides and C. korshinskii were markedly higher (p<0.01) than those in Z. jujuba and R. parvifolius. Among the three herbs, L. davurica and A. cristatum had significantly higher δ13C values than A. sacrorum (p<0.01). Leguminous species such as R. pseudoacacia, C. korshinskii, and L. davurica as well as a non-leguminous species with nitrogen-fixation capacity, H. rhamnoides, had higher δ13C values than other non-leguminous species with same life-form. The mean δ13C value increased by about 7 % from Yangling in the south to Shenmu in the north as climatic drought increased, and foliar
δ13C values differed much (p<0.001) among the seven sites. For nine species in the Loess Plateau, foliar δ13C values were significantly and negatively (p<0.001) correlated with the mean annual precipitation, moreover, an increase of 100 mm in annual precipitation would result
in a decrease of 1.2 ‰ in δ13C value. 相似文献
14.
Stable carbon isotope composition (δ13C), net photosynthetic rate (P
N), actual quantum yield of photosystem 2 (PS2) electron transport (ΦPS2), nitrogen content (Nc), and photosynthetic nitrogen use efficiency (PNUE) in the leaves of six broadleaf tree species were determined under field
environmental conditions. The six tree species were Magnolia liliflora Desr., M. grandiflora Linn., M. denudata Desr., Prunus mume (Sieb.) Sieb. et Zucc. cv. Meiren Men, P. mume (Sieb.) Sieb. et Zucc. f. alphandii (Carr.) Rehd., and P. persica (L.) Batsch. var. rubro-plena. The relationships among δ13C, ΦPS2, P
N, and PNUE, as well as their responses to Nc in the six species were also studied. Both P
N and δ13C negatively correlated with Nc, but ΦPS2 positively correlated with Nc. This indicated that with Nc increase, P
N and δ13C decreased, while ΦPS2 increased. There were weak negative correlations between δ13C and PNUE, and strong negative correlations (p<0.01) between ΦPS2 and PNUE. According to the variance analysis of parameters, there existed significant interspecific differences (p<0.001) of δ13C, P
N, ΦPS2, PNUE, and Nc among the tree seedlings of the six tree species, which suggests that the potential photosynthetic capacities depend on plant
species, irradiance, and water use capacity under field conditions. 相似文献
15.
16.
Spatial patterns of leaf nutrient traits of the plants in the Loess Plateau of China 总被引:4,自引:0,他引:4
The spatial patterns of leaf nutrient traits of plants in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi
and Shenmu, standing from south to north in the Loess Plateau of China, were studied. The results showed that of the 126 plant
samples in the Loess Plateau, the mean leaf organic carbon (C), nitrogen (N), phosphorus (P) and potassium (K) were 43.8,
2.41, 0.16 and 1.67%, respectively, and ranked in the order of C > N > K > P. Leaf C, N, P and K ranged from 32.6 to 54.8%,
0.82 to 4.58%, 0.06 to 0.35%, and 0.24 to 4.21%, respectively. The mean leaf C/N, C/P and N/P ratios were 21.2, 312 and 15.4,
respectively. It is indicated that leaf N in the Loess Plateau was significantly higher than those in Chinese and global flora,
but leaf P was significantly lower than that in global flora, which resulted in a higher N/P ratio in the Loess Plateau. The
results also showed that leaf C, N, P, K, C/N and C/P ratios varied significantly among the seven life-form groups, which
were trees, shrubs, herbages, evergreen trees, deciduous trees, C3 and C4 herbages, but leaf N/P ratio differed little among the seven life-forms. In the sampled species in the Loess Plateau, leaf
C was negatively correlated with leaf N, P and K, while leaf N, P and K were positively correlated with one another. In general,
leaf N/P ratio increased as the latitude and annual solar radiation increased and the mean annual rainfall and mean annual
temperature decreased. 相似文献
17.
山西朔县种子植物区系及其生态经济意义 总被引:10,自引:0,他引:10
上官铁梁;张峰;刘玉山 《武汉植物学研究》1991,9(4):355-362
朔县(现朔州市朔城区)植物种属相对丰富,具有维管束植物938种,隶属于420属,105科。其植物区系主要起源于古北大陆;种子植物属的地理成分复杂多样,以温带成分占绝对优势,具有典型的温带草原性质;与相邻地区植物区系的比较分析表明,联系最为密切的是蒙古草原植物区系,其次是黄土高原植物区系。该县植物资源利用应采取的对策是:既要合理开发利用,又要加强物种的保护。 相似文献
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