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11.
12.
Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N2 fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO2, and temperature 23/18 °C day/night temperaturesat 680 µmol mol1 CO2, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol1 CO2 (C340)After 34 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO2 and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 1729%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO2 mol H2O1)was also significantly increased Plants acclimated to elevatedCO2, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves instantaneouslyexposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO2, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO2 at 23 °C increased graduallyfrom approx 10 % at 100 µmol m1 s1 to >27 % at 1170 µmol m2 s1 In parallel, wateruse efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 In parallel,water use efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 to approx100 % at the highest irradiance Elevated CO2, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO2 and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N2, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO2, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO2, elevated temperature, water use efficiency, N2 fixation 相似文献
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14.
A quantitative analysis of the 14C-labelled assimilate suppliedby leaves on the main shoot to terminal meristem, stem, tillers,and roots was conducted during parallel periods of reproductiveand vegetative development in Lolium temulentum. The initial rate of entry of carbon into the shoot varied withthe area and photosynthetic efficiency of the assimilating leaf.Subsequently, respiratory losses of carbon during translocationand incorporation of assimilate at the site of utilization alsovaried. The combined effect of these differences resulted inthe supply of recently assimilated carbon being twofold greaterin reproductive shoots than in vegetative shoots, while withinshoots the carbon supply of the youngest fully expanded leafranged from four-or five-fold greater than the oldest leaf inyoung shoots, to two-or three-fold greater in older shoots.In both reproductive and vegetative shoots, the two or threeyoungest leaves thus dominated the supply of carbon for meristematicgrowth. Meristematic tissue in expanding leaves and leaf primordia atthe terminal meristem of the vegetative shoot received 1827per cent of the total shoot carbon. This meristem utilized aboutthe same proportion of shoot carbon when it developed into aninflorescence, indicating no major change in the level of meristematicactivity. The proportion of shoot carbon utilized in stem growthincreased as both reproductive and vegetative shoots aged; thisincreased meristematic activity in stem internodes was accompaniedby reduced export of carbon to roots, which received less than10 per cent of the shoot carbon when the experiments ended.The main shoot translocated 2030 per cent of its recentlyassimilated carbon to developing and rooted tillers, which assinks for carbon were thus as important as the terminal meristemand stem. This outward flow of carbon continued relatively uncheckedwhen donor and receptor shoots developed inflorescences. 相似文献
15.
G. J. A. RYLE 《The Annals of applied biology》1970,66(1):155-167
The movement of 14C-labelled assimilate to the terminal meristem, stem, mature leaves, tillers and roots was measured in Loliurn perenn and Lolium temulentum after exposure to 14C02 of the youngest fully-expanded leaf and, on fewer occasions, the oldest healthy leaf on the main shoot. During early vegetative growth, the terminal meristem, tillers and roots received most of the 14C exported from the youngest leaf. As the shoot aged, more 14C was exported to the terminal meristem and tillers and less to roots. When the stem became a sizeable sink for 14C at the six-leaf (L. temulentum) or eleven-leaf (L. perenne) stage, less 14C moved to tillers and much less to roots. The terminal meristem continued to receive 14 at a steady rate throughout late vegetative growth. The transition from vegetative to reproductive growth in both species was marked by an abrupt increase in the export of 14C to stem from the upper leaf, but there was little change in the proportion of 14C which moved to the developing leaves and incipient inflorescence at the terminal meristem. At the same time, less 14C moved to tillers and much less to roots. Immediately before ear emergence, the export of 14C from the upper leaf (flag leaf) to the stem declined and the proportion moving to the ear increased, reaching a maximum of 55–75% as the ear emerged. The relative patterns of export of upper and lower leaves showed that while some 14 moved from each leaf to all meristems, the proximity of actively growing meristems appeared to be the main factor which determined the destination of most exported 14C. The distribution of 14C from upper and lower leaves was most alike in young vegetative plants of L. perenne. At later stages of development of both species, the terminal meristem and stem received most 1414C from the upper leaf, while roots and tillers received mos 1414C from the oldest leaf at the base of the shoot. 相似文献
16.
17.
Bryce, J. H. and ap Rees, T. 1985. Comparison of the respiratorymetabolism of Plantago lanceolata L. and Plantago major L.J.exp. Bot. 36 15591565. The aim of this work was to discover if the respiratory metabolismof the roots of Plantago lanceolata L. differed from that ofthe roots of Plantago major L. Measurements of oxygen uptakeand dry weight of excised root systems during growth of seedlingsprovided evidence that the two species differed in the amountof respiration needed to support a given increase in dry weight.Excised root systems were given a 6-h pulse in [U-14C]sucrosefollowed by a 16.5-h chase in sucrose. The detailed distributionof 14C amongst the major components of the roots at the endof the pulse and the chase revealed no significant differencebetween the two species. Patterns of 14CO2 production from [1-14C],[2-14C], [3,4-14C], and [6-14C]glucose of excised root systemsfrom plants of three ages were similar for the two species.It is suggested that there is no conclusive evidence for anysignificant inherent difference in the respiratory metabolismof the roots of the two species. Key words: 14C sugar metabolism, respiration, roots, Plantago 相似文献
18.
Clonal plants of white clover (Trifolium repens L.), grown singly in pots of Perlite and solely dependent for nitrogen on root nodule N2 fixation, were maintained in controlled environments which provided four environments: 18/13 °C day/night temperature at 340 and 680 μmol mol?1 CO2 and 20·5/15·5°C day/night temperature at 340 and 680 μmol mol?1 CO2. The daylength was 12 h and the photon flux density 500±25 μmol m?2 s?1 (PFD). All plants were defoliated for about 80d, nominally every alternate day, to leave the youngest expanded leaf intact on 50% of stolons, plus expanding leaves (simulated grazing). Elevated CO2 increased the yield of biomass removed at defoliation by a constant 45% during the second 40d of the experiment and by a varying amount in the first half of the experiment. Elevated temperature had little effect on biomass yield. Nitrogen, as a proportion of the harvested biomass, was only fractionally affected by elevated CO2 or temperature. In contrast, N2 fixation increased in concert with the promoting effect of elevated CO2 on biomass production. The increased yield of biomass harvested in 680 μmol mol?1 CO2 was primarily due to the early development and continued maintenance of more stolons. However, the stolons of plants grown in elevated CO2 also developed leaves which were heavier and slightly larger in area than their counterparts in ambient CO2. The conclusion is that, when white clover plants are maintained at constant mass by simulated grazing, they continue to respond to elevated CO2 in terms of a sustained increase in biomass production. 相似文献
19.
Rapid recycling of triose phosphates in oak stem tissue 总被引:10,自引:3,他引:7
S. A. HILL J. S. WATERHOUSE E. M. FIELD V. R. SWITSUR T. AP REES 《Plant, cell & environment》1995,18(8):931-936
We report the carbon-13 and oxygen-18 isotope ratios in cellulose from the early and late wood of pedunculate oak (Quercus robur L.). The δ13 C value of the early wood correlates best with that of the late wood of the previous year. The δ18O value of the early wood correlates best with that of the late wood of the same year. We suggest that a biochemical explanation of these data is that there is a rapid cycle between hexose monophosphates and triose phosphates in oak stem tissue during cellulose synthesis. Evidence in support of this explanation is provided by the intramolecular distribution of 14C in labelled fructose extracted from cores of wood that had been supplied with [1?14C]- and [6-14C]glucose. 相似文献
20.
CM Ward AP Wilkinson S Bramham HA Lee HW-S Chan GW Butcher A Hutchings MRA Morgan 《Mycotoxin Research》1990,6(2):73-83
From a single aflatoxin B1 oxime — bovine serum albumin conjugate, polyclonal and monoclonal antibody preparations were produced. The four rabbit polyclonal antisera were specific for aflatoxin Bi in a microtitration plate enzyme — linked immunosorbent assay. The monoclonal antibodies showed a wide range of differing specificities, recognizing, for example, aflatoxins B1, B2, G1 and G2; B1 and B2; B1 and G1; and G1 alone. No antibody preparations reacted with aflatoxin M1. The significance of these results to the strategy of anti-aflatoxin antibody production for use in quantitative enzyme immunoassays is discussed. 相似文献