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81.
The multivariate Poisson-log normal distribution 总被引:6,自引:0,他引:6
82.
83.
The dependence of respiration on photosynthetic substrate supply and temperature: integrating leaf, soil and ecosystem measurements 总被引:5,自引:0,他引:5
IAIN P. HARTLEY ANNA F. ARMSTRONG RAMESH MURTHY† GREG BARRON-GAFFORD‡ PHIL INESON OWEN K. ATKIN 《Global Change Biology》2006,12(10):1954-1968
Interactions between photosynthetic substrate supply and temperature in determining the rate of three respiration components (leaf, belowground and ecosystem respiration) were investigated within three environmentally controlled, Populus deltoides forest bays at Biosphere 2, Arizona. Over 2 months, the atmospheric CO2 concentration and air temperature were manipulated to test the following hypotheses: (1) the responses of the three respiration components to changes in the rate of photosynthesis would differ both in speed and magnitude; (2) the temperature sensitivity of leaf and belowground respiration would increase in response to a rise in substrate availability; and, (3) at the ecosystem level, the ratio of respiration to photosynthesis would be conserved despite week‐to‐week changes in temperature. All three respiration rates responded to the CO2 concentration‐induced changes in photosynthesis. However, the proportional change in the rate of leaf respiration was more than twice that of belowground respiration and, when photosynthesis was reduced, was also more rapid. The results suggest that aboveground respiration plays a key role in the overall response of ecosystem respiration to short‐term changes in canopy photosynthesis. The short‐term temperature sensitivity of leaf respiration, measured within a single night, was found to be affected more by developmental conditions than photosynthetic substrate availability, as the Q10 was lower in leaves that developed at high CO2, irrespective of substrate availability. However, the temperature sensitivity of belowground respiration, calculated between periods of differing air temperature, appeared to be positively correlated with photosynthetic substrate availability. At the ecosystem level, respiration and photosynthesis were positively correlated but the relationship was affected by temperature; for a given rate of daytime photosynthesis, the rate of respiration the following night was greater at 25 than 20°C. This result suggests that net ecosystem exchange did not acclimate to temperature changes lasting up to 3 weeks. Overall, the results of this study demonstrate that the three respiration terms differ in their dependence on photosynthesis and that, short‐ and medium‐term changes in temperature may affect net carbon storage in terrestrial ecosystems. 相似文献
84.
四数獐牙菜的胚胎学及其系统学意义 总被引:16,自引:0,他引:16
四数獐牙菜花药四室,药壁发育为双子叶型;绒毡层腺质型。小孢子母细胞减数分裂为同时型,
四分体的排列方式为四面体形;成熟花粉为3-细胞。子房2心皮,2心皮连接处强烈内凸,4列胚珠。薄
珠心,单珠被,直生胚珠。胚囊发育为蓼型。胚乳发育为核型。胚胎发育为茄型酸浆I变型。反足细胞
在胚囊成熟时期宿存。果实成熟时,种子只发育至球型胚阶段。承珠盘存在。与已研究的獐牙菜种类
的胚胎特征相比较,该种存在三个显著的特点:直生胚珠,心皮连接处强烈内凸,承珠盘存在。这三个特
征目前仅在龙胆族中的花锚属中发现。经过性状分析,它们均是演征,此三个共有演征表明四数獐牙菜
与花锚属是一单系群,它们的亲缘关系最近。这与Yun &; Kupfer(1995)的分子证据部分吻合,因为分
子系统树上的花锚单系支包括花锚、四数獐牙菜和北美的密花属(广义獐牙菜属中的密花组),而后者的
胚胎学特征未有任何报道。胚胎学研究暗示四数獐牙菜的分类学等级有待重新评价,广义的獐牙菜属 有可能不是一单系发生群。 相似文献
85.
CHRISTOPHER M. HARDY EVELYN S. KRULL DIANA M. HARTLEY RODERICK L. OLIVER 《Molecular ecology》2010,19(1):197-212
Determining the source and flow of carbon, energy and nutrients through food webs is essential for understanding ecological connectivity and thus determining the impact of management practices on biodiversity. We combined DNA sequencing, microarrays and stable isotope analyses to test whether this approach would allow us to resolve the carbon flows through food webs in a weir pool on the lower Murray River, a highly impacted, complex and regulated ecosystem in southern Australia. We demonstrate that small fish in the Murray River consume a wide range of food items, but that a significant component of carbon and nitrogen entering the food web during dry periods in summer, but not spring, is derived from nonconventional sources other than in-channel primary producers. This study also showed that isotopic analyses alone cannot distinguish food sources and that a combined approach is better able to elucidate food-consumer dynamics. Our results highlight that a major river ecosystem, stressed by reduced environmental flows, can rapidly undergo significant and previously undetected changes that impact on the ecology of the system as a whole. 相似文献
86.
87.
Z LATIFFAH K HARIKRISHNA S G TAN S H TAN F ABDULLAH Y W HO 《The Annals of applied biology》2002,141(2):133-142
Use of Crassulacean acid metabolism (CAM) plants in México and worldwide has a long history, but the morphological and photosynthetic aspects of these plants have only been considered recently. Emphasis in this article is on the daily net CO2 uptake ability by three species of agaves and three species of cacti that are currently extensively cultivated in México for beverages, food, fodder, and forage ‐ Agave mapisaga, A. salmiana, A. tequilana, Opuntia ficus‐indica, O. robusta and Stenocereus queretaroensis. Data under controlled conditions are used to help interpret seasonal net CO2 uptake patterns observed in the field. These CAM plants have instantaneous and total daily net CO2 uptake values similar to those for highly productive C3 and C4 crops. The future increase in the cultivated area of CAM plants will have both agronomical and ecological ramifications because of the ability of these plants to endure prolonged drought and to sequester carbon during extended dry periods when few C3 and C4 crops and non‐CAM native plants can fix atmospheric CO2. 相似文献
88.
APPLICATION of strychnine or d-tubocurarine to the exposed cerebral cortex leads after a few minutes to abnormality in somatosensory evoked potentials1,2. This consists of a surface negative wave (peak latency, 21–23 ms) which attains an amplitude five to twenty times greater than that of the normal evoked potentials and probably reflects excessive depolarization of the apical dendrites of pyramidal neurones. We wish to report the blocking of this effect by prior application of eserine to the cortex. 相似文献
89.
A. H. LINTON KATHERINE HOWE CHRISTINE L. HARTLEY HELEN M. CLEMENTS M. H. RICHMOND A. D. OSBORNE 《Journal of applied microbiology》1977,42(3):365-378
Presumptive coliform counts and the distribution of Escherichia coli O-serotypes were investigated in chicken rectal contents (175) abdominal cavities (152) and on the carcasses of 44 which had been commercially raised, slaughtered and prepared for sale. Large numbers of E. coli resistant to at least one antibacterial agent were found at each site; comparison of the O-serotypes suggested heavy contamination of the carcass with strains from the gut. The range of O-serotypes was similar to that found in man and some public health implications of cross-infection particularly by handling uncooked birds in the kitchen, are discussed. 相似文献
90.
The Effect of Current Photosynthesis on the Origin of Translocates in Old Tomato Leaves 总被引:3,自引:0,他引:3
The rate of carbon transport from an old tomato leaf (54 days),grown at 80 W m2, was measured under light flux densitiesbetween 7 and 90 W m2. Under low light, the rate of carbontransport over a 6 h period was about 1 mg C dm2 h1,well in excess of the concurrent photosynthetic rate. The lossfrom these leaves of 14C-leaf assimilate which was fixed beforethe experimental period amounted to 62 per cent of the totalinitial uptake and was higher than that from leaves with higherconcurrent photosynthetic rates. The higher loss of 14C fromleaves with low photosynthetic rates was due to a greater contributionof 14C from the starch and residue fractions. The rate of transportappeared to be determined by the concentration of the labilesucrose, not the total sucrose concentration. In comparisonwith young fully-expanded tomato leaves (Ho, 1976) the sizeof the labile sucrose pool appeared to decrease with age. Thephotosynthesistranslocation coefficient was low (k1k2=021)for an old tomato leaf. Based on these results a scheme of carbonpartitioning in relation to translocation is proposed. Criteriafor assessing the efficiency of translocation in leaves arediscussed. 相似文献