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141.
沙地云杉苗期生长与干物质生产关系的研究 总被引:21,自引:4,他引:17
本文用不同_的模型定量地研究了沙地云杉苗期的生长规律、季节动态及不同生长时期干物质在各器官之间的分配规律。1)1年生幼苗一直保持较高的生长速度,根生长尤为迅速。5年生幼苗在接近生长上限时,增长越来越慢。2)根、茎、叶干物质的生产符合理查德模型;根、茎、叶干重与全株干重之百分比表现出不同的变化趋势,反映了于物质在各器官中的分配规律。3)不同年度各器官的干重变化反映了由于自疏造成的叶的脱落和部分枝的脱落情况。4)各模型的相关系数几乎都达到了极显著的水平。 相似文献
142.
James A. Bunce 《Physiologia plantarum》1992,86(1):173-179
The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO2 usually observed in C3 plants sometimes does not persist. Experiments were conducted to test whether the patterns of response to the environment during growth were consistent with the hypotheses that photosynthetic adjustment to elevated CO2 concentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sugar beet (Best vulgaris L. cv. Mono Hye-4) were grown from seed at 350 and 700 μl? CO2, at 20 and 25°C, at a photon flux density of 0.5 and 1.0 mmol m?2 S?1 and with three nutrient regimes until the third trifoliolate leaf of soybean or the sixth leaf of sugar beet had finished expanding. Net rates of CO2 exchange of the most recently expanded leaves were then measured at both 350 and 700 μl 1?1 CO2. Plants grown at the elevated CO2 concentration had net rates of leaf CO2 exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350 μl 1?1 CO2 and when averaged over all treatments. Negative photosynthetic adjustment to elevated CO2 concentration was not greater at 20 than at 25°C, was not greater at a photon flux density of 1.0 than at 0.5 mmol m?2 S?1 and was not greater with limiting nutrients. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO2 concentration, with net rates of CO2 exchange the next day equal to those of leaves of plants grown from seed at the elevated concentration of CO2. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO2. 相似文献
143.
M FIGUERAS J PUJAL A SALEH R SAVE M PAGES A GODAY 《The Annals of applied biology》2004,144(3):251-257
Rabl7 is a Late Embryogenesis Abundant (LEA) protein from maize, which accumulates largely during embryogenesis and also in vegetative tissues when subjected to stress conditions. We have analysed the effect of Rab 17 expression under a constitutive promoter in vegetative tissues of transgenic Arabidopsis thaliana plants. These transgenic plants have higher sugar and proline contents, and also higher water loss rate under water stress. In addition, these plants are more tolerant than non-transformed controls to high salinity and recover faster from mannitol treatment. Our results point to a protective effect of Rabl7 protein in vegetative tissues under osmotic stress conditions. 相似文献
144.
Relations between stomatal closure, leaf turgor and xylem vulnerability in eight tropical dry forest trees 总被引:15,自引:2,他引:15
T. J. BRODRIBB N. M. HOLBROOK E. J. EDWARDS & M. V. GUTIÉRREZ 《Plant, cell & environment》2003,26(3):443-450
This study examined the linkage between xylem vulnerability, stomatal response to leaf water potential (ΨL), and loss of leaf turgor in eight species of seasonally dry tropical forest trees. In order to maximize the potential variation in these traits species that exhibit a range of leaf habits and phenologies were selected. It was found that in all species stomatal conductance was responsive to ΨL over a narrow range of water potentials, and that ΨL inducing 50% stomatal closure was correlated with both the ΨL inducing a 20% loss of xylem hydraulic conductivity and leaf water potential at turgor loss in all species. In contrast, there was no correlation between the water potential causing a 50% loss of conductivity in the stem xylem, and the water potential at stomatal closure (ΨSC) amongst species. It was concluded that although both leaf and xylem characters are correlated with the response of stomata to ΨL, there is considerable flexibility in this linkage. The range of responses is discussed in terms of the differing leaf‐loss strategies exhibited by these species. 相似文献
145.
Diseased fruit bodies of Agaricus bitorquis, with similar symptoms to those caused by dry bubble on Agaricus bisporus, were observed in some Spanish crops during summer 1999. Isolates of Verticillium fungicola from A. bitorquis and A. bisporus were submitted to different temperatures and to prochloraz–Mn sensitivity tests. All the isolates collected from A. bitorquis and A. bisporus were identified as V. fungicola var. fungicola. Artificial infections of A. bisporus and A. bitorquis with V. fungicola var. fungicola are also described in the present study. The appearance of natural infections of V. fungicola var. fungicola in A. bitorquis crops could well be due to the growing temperatures used in Spain, which are considerably below those used in other countries. 相似文献
146.
Kees-Jan Van Groenigen Johan Six David Harris‡ Herbert Blum§ Chris Van Kessel 《Global Change Biology》2003,9(12):1751-1762
Reduced soil N availability under elevated CO2 may limit the plant's capacity to increase photosynthesis and thus the potential for increased soil C input. Plant productivity and soil C input should be less constrained by available soil N in an N2‐fixing system. We studied the effects of Trifolium repens (an N2‐fixing legume) and Lolium perenne on soil N and C sequestration in response to 9 years of elevated CO2 under FACE conditions. 15N‐labeled fertilizer was applied at a rate of 140 and 560 kg N ha?1 yr?1 and the CO2 concentration was increased to 60 Pa pCO2 using 13C‐depleted CO2. The total soil C content was unaffected by elevated CO2, species and rate of 15N fertilization. However, under elevated CO2, the total amount of newly sequestered soil C was significantly higher under T. repens than under L. perenne. The fraction of fertilizer‐N (fN) of the total soil N pool was significantly lower under T. repens than under L. perenne. The rate of N fertilization, but not elevated CO2, had a significant effect on fN values of the total soil N pool. The fractions of newly sequestered C (fC) differed strongly among intra‐aggregate soil organic matter fractions, but were unaffected by plant species and the rate of N fertilization. Under elevated CO2, the ratio of fertilizer‐N per unit of new C decreased under T. repens compared with L. perenne. The L. perenne system sequestered more 15N fertilizer than T. repens: 179 vs. 101 kg N ha?1 for the low rate of N fertilization and 393 vs. 319 kg N ha?1 for the high N‐fertilization rate. As the loss of fertilizer‐15N contributed to the 15N‐isotope dilution under T. repens, the input of fixed N into the soil could not be estimated. Although N2 fixation was an important source of N in the T. repens system, there was no significant increase in total soil C compared with a non‐N2‐fixing L. perenne system. This suggests that N2 fixation and the availability of N are not the main factors controlling soil C sequestration in a T. repens system. 相似文献
147.
SEBASTIAN SOBEK GRETE ALGESTEN† ANN-KRISTIN BERGSTRÖM† MATS JANSSON† LARS J. TRANVIK 《Global Change Biology》2003,9(4):630-641
The regulation of surface water pCO2 was studied in a set of 33 unproductive boreal lakes of different humic content, situated along a latitudinal gradient (57°N to 64°N) in Sweden. The lakes were sampled four times during one year, and analyzed on a wide variety of water chemistry parameters. With only one exception, all lakes were supersaturated with CO2 with respect to the atmosphere at all sampling occasions. pCO2 was closely related to the DOC concentration in lakes, which in turn was mainly regulated by catchment characteristics. This pattern was similar along the latitudinal gradient and at different seasons of the year, indicating that it is valid for a variety of climatic conditions within the boreal forest zone. We suggest that landscape characteristics determine the accumulation and subsequent supply of allochthonous organic matter from boreal catchments to lakes, which in turn results in boreal lakes becoming net sources of atmospheric CO2. 相似文献
148.
红壤旱坡地桔园覆盖的生态效应及经济效益评价 总被引:11,自引:2,他引:9
柑桔是南方红壤地区栽培的主要果树种类,栽培面积达1126×106hm2。柑桔是一种常绿果树,生长量大,挂果期长,周年需要消耗大量的水分。我国南方红壤地区虽然雨水充沛,但降水季节分布不均,柑桔果实迅速生长的7~10月正是该地区雨水少、蒸发量大的伏秋干旱季节。经常性的伏秋干旱是制约我国柑桔产量和质量进一步提高的主要障碍因素之一。桔园夏秋进行秸秆覆盖可以降温[1]、保水[2]、防止杂草生长[3]等,但桔园应用地膜覆盖及常年连续覆盖对桔园的生态效应方面的研究较少,为此我们开展了这方面的工作,并通过连续3a的产量及产值分析覆盖桔园的经… 相似文献
149.
Increased intracellular calcium concentration ([Ca2+]i) is required for smooth muscle contraction. In tracheal and other tonic smooth muscles, contraction and elevated [Ca2+]i are maintained as long as an agonist is present. To evaluate the physiological role of steady-state increases in Ca2+ on tension maintenance, [Ca2+]i was elevated using ionomycin, a Ca2+ ionophore or charybdotoxin, a large-conductance calcium-activated potassium channel (KCa) blocker prior to or during exposure of tracheal smooth muscle strips to Ach (10–9 to 10–4
M). Ionomycin (5 µM) in resting muscles induced increases in [Ca2+]i to 500±230 nM and small increases in force of 2.6±2.3 N/cm2. This tension is only 10% of the maximal tension induced by ACh. Charybdotoxin had no effect on [Ca2+]i or tension in resting muscle. After pretreatment of muscle with ionomycin, the concentration-response relationship for ACh-induced changes in tension shifted to the left (EC50=0.07±0.05 µM ionomycin; 0.17±0.07 µM, control, p<0.05). When applied to the muscles during steady-state responses to submaximal concentrations of ACh, both ionomycin and charybdotoxin induced further increases in tension. The same magnitude increase in tension occurs after ionomycin and charybdotoxin treatment, even though the increase in [Ca2+]i induced by charybdotoxin is much smaller than that induced by ionomycin. We conclude that the resting muscle is much less sensitive to elevation of [Ca2+]i when compared to muscles stimulated with ACh. Steady-state [Ca2+]i limits tension development induced by submaximal concentrations of ACh. The activity of KCa moderates the response of the muscle to ACh at concentrations less than 1 µM. 相似文献
150.
The high-affinity uptake system of phosphatelimited cyanobacterium Anacystis nidulans [Synechococcus leopoliensis (Raciborski) Komarek] is characterized by a threshold value below which uptake cannot occur. Here it is shown that, if phosphate-limited cyanobacteria are challenged with a short pulse of high phosphate concentration that appreciably exceeds this threshold value, the uptake system undergoes an adaptive response, leading to the attainment of new kinetic properties and a new threshold value. These new properties are maintained for several hours after the pulse. A notable characteristic of this new state is a wide linear dependence of the uptake rate on the external phosphate potential that is a function of the driving force of the uptake process. According to theoretical arguments it is shown that this “linear operation mode” can be explained by the simultaneous operation of several uptake systems with different, staggered threshold values and kinetic properties. Moreover, the new linear uptake properties, in turn, reflect the prehistory of phosphate supply experienced by the population. The consequences of this result with regard to environmental fluctuations of the phosphate concentration in lakes are discussed. 相似文献