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1.
The Carbon Economy of Rubus chamaemorus L. II. Respiration 总被引:1,自引:0,他引:1
Respiratory activity and seasonal changes in carbohydrate contentof the storage organs of Rubus chamaemorus L. have been investigated.Leaf dark respiration rate increases in a non-linear mannerfrom 0·7 mg CO2 evolved dm2 h1 at 0 °Cto 4·6 rng CO2 evolved dm2 hh1 at 30 °C.Root and rhizome respiration rates increase from 1 µ1O2 uptake g1 fresh weight h1 at 0.7 ° C to10 µ10, uptake g1 f. wt h1 at 20 °C.Rhizome carbohydrate reserves decline from a September peakof 33 per cent alcohol insoluble d. wt to 16 per cent in May. The circumpolar distribution of R. chamaemorus is discussedin relation to the evidence presented here and in the precedingpaper of the series. 相似文献
2.
MATTSSON M.; LUNDBORG T.; LARSSON M.; LARSSON C.-M. 《Journal of experimental botany》1992,43(1):25-30
Barley (Hordeum vulgare L., cvs Golf, Mette, and Laevigatum)was grown under nitrogen limitation in solution culture untilnear maturity. Three different nitrogen addition regimes wereused: in the HN culture the relative rate of nitrate-Naddition (RA) was 0·08 d1 until day 48 and thendecreased stepwise to, finally, 0·005 d1 duringgrain-filling; the LN culture received 45% ofthe nitrogen added in HN; the CN culture was maintainedat RA 0·0375 d1 throughout. Kinetics of net nitrateuptake were measured during ontogeny at 30 to 150 mmol m3external nitrate. Vmax (which is argued to reflect the maximuminflux rate in these plants) declined with age in both HN andLN cultures. A pronounced transient drop was observed just beforeanthesis, which correlated in time with a peak in root nitrateconcentration. Similar, but less pronounced, trends were observedin CN. The relative Vmax (unit nitrogen taken up per unit nitrogenin plants and day) in all three cultures declined from 1·32·3d1 during vegetative growth to 0·10·7d1 during generative growth. These values are in HN andLN cultures 15- to more than 100-fold in excess of the demandset by growth rates throughout ontogeny. Predicted balancingnitrate concentrations (defined as the nitrate concentrationrequired to support the observed rate of growth) were below6·0 mmol m3 in HN and LN cultures before anthesisand then decreased during ontogeny. In CN cultures the balancingnitrate concentration increased during grain-filling. Apartfrom the transient decline during anthesis, most of the effectof ageing on relative Vmax can be explained in terms of reducedcontribution of roots to total biomass (R:T). The loss in uptakeper unit root weight is largely compensated for by the declinewith time in average tissue nitrogen concentrations. The quantitativerelationships between relative Vmax and R:T in ageing plantsare similar to those observed for vegetative plants culturedat different RAs. The data support the contention that the capacity for nitrateacquisition in N-limited plants is under general growth control,rather than controlled by specific regulation of the biochemicalpathway of nitrate assimilation. Key words: Barley, nitrogen concentration, root: total plant biomass ratio, Vmax 相似文献
3.
A response surface was developed by regression analysis to quantifythe seasonal respiratory losses by a kiwifruit [Actinidia deliciosa(A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv.Hayward] berry growing in Fresno, CA. The equation of the surfacewas LNRESP = 1·622 + 0·0697 x TEMP 0·0472x DAY + 0·000165 x DAYSQ, where LNRESP is the naturallogarithm of the respiration rate (nmol CO2 g d. wt1s1), TEMP is fruit temperature (°C), DAY is the numberof days after flowering, and DAYSQ is the square of the numberof days after flowering. Respiratory losses for a fruit witha final dry mass of 18·5 g were calculated to be 5·57and 5·92 g glucose per fruit per season in 1985 and 1986,respectively. Maintenance respiration was estimated to be 2·84and 3·19 g glucose per fruit per season for 1985 and1986, respectively. The total calculated bioenergetic cost ofkiwifruit berry growth and respiration was 25·25 and25·60 g glucose per fruit per season for 1985 and 1986,respectively. Respiratory losses, expressed as a proportionof the total carbohydrate required for fruit growth, were significant(mean 22·6%). The cost of fruit growth was estimatedto be very similar for two cooler sites (Davis and Watsonville)but estimates of maintenance respiration based on Fresno fruitrespiration data were unrealistically low for the Watsonvillesite. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward, kiwifruit, growth respiration, maintenance respiration, bioenergetic costs, model 相似文献
4.
The effects of various levels of copper on the uptake and distributionof copper in Chrysanthemum morifolium grown in solution cultureand peat-sand have been examined. Whole plants growing in shortdays were sampled at regular intervals, divided into roots,stem, leaves and lateral shoots, and analysed for copper. Thepartitioning of copper between these tissues showed that a relativelylarge proportion (3040 per cent) of the total plant copperwas accumulated in the roots of normal plants during the harvestingperiod, compared with approximately 10 per cent in the rootsof copper deficient plants. Whilst the copper content (ug g1) of leaves and stemfrom normal plants was negatively correlated with the amountof dry matter produced (P < 0·001), the correspondingcopper deficient tissues showed little variation in copper contentwith increases in tissue dry weight. A more detailed investigationof the copper content of leaves from normal plants showed thatgradients existed within the plant with respect to both leafposition and time of harvest which could be described by a singlecubic surface equation (P < 0·001). 相似文献
5.
Ion Exchange in Sphagnum and its Relation to Bog Ecology 总被引:17,自引:0,他引:17
In Sphagnum cuspidatum unesterified polyuronic acids form 12per cent. of the dry weight; in S. acutifolium 25 per cent,of the dry weight. A good correlation has been found for Sphagnabetween the content of unesterified polyuronic acid and thecation exchange ability, and between cation exchange abilityand height of normal habitat above the water table. Anion exchangeability in Sphagna is less than 0.0026 m.eq./g. D.W. comparedwith about 1.2 m.eq./g. D.W. for cations at pH values above7. In natural conditions the exchange sites are, however, onlypartly dissociated. The production of new plant material ina bog dependent on rainwater for nutrients can be sufficientto maintain the pH below 4.5, but on average in England onlyof the order of 2 per cent, of the monovalent cations otherthan H+ could be retained in exchangeable form. A greater proportionof polyvalent cations could be retained. The kinetics of cation exchange are consistent with a heterogeneousexchange phase containing regions of high charge density andregions with lower charge density. At equilibrium the proportionsof different cations in the exchange phase are largely explicableby a Donnan distribution, but there are notable exceptions.Two estimates based on Donnan distribution suggest that withlow external pH and/or low cation concentration the apparentconcentration of exchange sites may be 2-3 eq./l., falling withrise in pH and/or increase in cation concentration to 0-9-1-5 eq./l. The apparent dissociation coefficient also variesin these conditions from 2 x 102 to 1 x 104. 相似文献
6.
Enzymatic hydrolysis of starch in lucerne (Medicago sativa L.)taproots is the conventional method used to determine the quantityof carbohydrates allocated to regrowth. Etiolated growth froma taproot could be used to quantify total root biomass allocatedto regrowth. This study compared concentrations of non-structuralcarbohydrates, as measured by -amylase hydrolysis of starchto glucose, to concentrations of non-structural biomass, asmeasured by etiolated growth from lucerne taproots placed inan incubator and plants in situ. The concentration of starchfrom enzymatically assayed taproots was 325 g kg-1 expressedas glucose equivalents. Etiolated growth and weight loss byrespiration from plants grown in the incubator accounted for524 g of actual biomass per kg of root. There was 46·2g kg-1 of N, 3·1 of P, and 33·1 of K in the etiolatedgrowth. An 88% increase in etiolated growth dry weight was observedfrom plants in situ compared to taproots placed in the incubator.Accurate quantification on non-structural biomass should notbe limited to sampling just the taproot, but must included theentire root system. Compared to determining non-structural carbohydratesby enzymatic hydrolysis of starch, the procedure used in determiningnon-structural biomass by etiolate growth gave results in unitsrelative to the plant. The use of etiolate growth also providedinformation on mineral nutrient partitioning from root to shoots,was less technically demanding, and could be applied to theentire root system.Copyright 1993, 1999 Academic Press Medicago sativa, root carbohydrates, etiolated growth, taproot 相似文献
7.
The growth of lucerne var. Europe was examined in the fieldduring 1976. The annual dry matter production of unirrigatedlucerne during 1976, with no nitrogen fertilizer application,was 82.5 per cent greater than unirrigated S.24 perennial ryegrass,with a nitrogen application of 384 kg ha1. The mean aboveground growth rate of lucerne was 7.3 g DM m2 day1between March and early June, of which stem material contributeda maximum of 76.5 per cent. Significant losses of leaves andstems occurred from the end of April, indicating a loss of potentialforage material. Nitrogen analyses of the above ground crop suggested that in56 days lucerne yielded 10.7 per cent more nitrogen than didS.24 annually with a nitrogen fertilizer addition of 280 kgha1. Between 13 and 57 per cent of the daily photosynthate is translocatedbelow ground. Medicago sativaL, lucerne, dry matter production, canopy structure, nitrogen analyses 相似文献
8.
During the first 100 days after sowing (March-June) the followingchanges took place at the terminal shoot apices of Picea sitchensisseedlings: plastochrones (T) decreased from over 24 h to 4 h;apical domes enlarged from less than 0·20 mm to 0·45mm diameter (D); the projected area of tissuesproduced by the apical domes (i.e. viewed from above) increasedin amount from less than 0·012 to 0·024 mm2 day-1;about 15 per cent of this tissue was re-invested in the apicaldomes, the rest was used to produce primordia; and the volume-doublingtimes of the apical dome tissues decreased from over 150 h to50 h. After 100 days there was no further re-investment in theapical domes, but the domes did not decrease abruptly in size.Less tissue was produced per day, but the primordia were smallerso that the rate of primordia formation did not fall precipitously.Plastochrone ratios were inversely related to D, but the relationshipbetween T and D depended on whether T was decreasing or increasing.Progenies which were known to be fast growing tended to build-uptheir apical domes rapidly (i.e. have large re-investmentratios) and to be capable of producing small primordia.These attributes can evidently be evaluated on seedlings andcould help to lessen the cost of tree breeding progeny-testprogrammes. meristem, Picea sitchensis, Sitka spruce, growth, shoot apex 相似文献
9.
The Structure and Function of Pine Forest in Central Himalaya. I. Dry Matter Dynamics 总被引:2,自引:0,他引:2
The present study deals with structure and function of fourareas of Himalayan chir pine forest. Tree layer was monospecificon all sites with varied density and basal cover in the rangeof 5401630 individuals per ha and 25·047·2m2ha1, respectively. Shrubs having low density were sparselydistributed. All allometric equations relating to biomass ofdifferent components, to circumference at breast height (cbh)were significant, with the exception of that for cone biomass.Total vegetation biomass (115236 t ha1) was distributedas 113283 t ha1 in trees. 0·560·82t ha1 in shrubs and 1·632·57 t ha1in herbs. Total forest floor biomass including herbaceous litterranged between 9·6 and 13·6 t ha1. Of thetotal annual litter fall (4·267·38 t ha1),60·375·1 per cent was distributed in leaflitter and 24·939·7 per cent in wood litter.Turnover rate of tree litter varied from 0·45 to 0·53,whereas rates for shrubs and herbs were assumed to 1. Net primaryproduction of total vegetation ranged between 9·91 and21·2 t ha1 year1, of which the contributionof trees, shrubs and herbs was 76·5 88·1per cent 0·61·8 per cent and 11·321·5per cent, respectively. A compartment model of dry matter onthe basis of mean data across sites was developed to show drymatter storage and flow of dry matter within the ecosystem. Pinus roxburghii forest, biomass, litter fall, net primary production, compartmental transfer 相似文献
10.
Wheat (Triticum sativum L. cv. Nisu) grown in 0·5 Hoaglandssolution containing sub-toxic concentrations of S-ethyl dipropylthiocarbamate(EPTQ (0,0·0625,0·125,0·25, and 0·5p.p.m.w.) were exposed to 14C-ring labelled-2-chloro-4-ethylamino-6-isopropylamino-s-triazine(atrazine). Total 14C-atrazine absorption was increased to 182per cent in wheat treated with 05 p.p.m.w. EPTC when comparedto the EPTC untreated wheat. Detoxification and metabolism ofEPTC were not appreciably altered by EPTC pretreatment. Thisresulted in an increased atrazine content in the wheat leavespretreated with 0·5 p.p.m.w. EPTC that amounted to 370per cent of the unchanged atrazine present in the leaves ofEPTC untreated wheat. 相似文献
11.
Growth of oil palm seedlings over the period 231 weeksafter planting in the nursery was studied using growth-analysistechniques. Curves of the Gompertz type were fitted to the basicdata of plant dry weight and leaf area, and from the equationsof the fitted curves, net assimilation rate (EA), relative growth-rate(Rw), and relative leaf growth-rate (RA) were calculated. The low values of EA (0.16-031 g/dm2/week) and Rw (1.42.2per cent./per day) confirm earlier work on oil palm seedlings.The time trend of increasing EA and RW over the period studiedis associated with steadily increasing solar radiation overthe second half of the period. Leaf-area ratio is markedly affected by transplanting, and asthis unbalance of leaf area/total dry weight has been shownto be associated with low rates of EA in seedlings, it is suggestedthat the low values of EA and RW in the first half of the experimentalperiod are due to the effect of transplanting. These findings are discussed in relation to current nurserypractice. 相似文献
12.
SENGUPTA B.; NANDI A. S.; SAMANTA R. K.; PAL D.; SENGUPTA D. N.; SEN S. P. 《Annals of botany》1981,48(5):705-716
Of the 560 leaf samples belonging to 259 species of green plantsexamined more than 50 per cent of the Angiosperms and 25 percent of the Pteridophytes and Gymnosperms revealed the presenceof N2-fixing micro-organisms in their phyllosphere. Plants particularlyremarkable in this respect are orchids and several other epiphytes,Scindapsus officinalis, Ficus and cucurbits. Most of the isolatesappear to be biotypes of Klebsiella pneumoniae. The more activestrains fixed more than 5 mg N g1 glucose utilized andreduced more than 100 nmol C2H2 mg1 cell d. w h1. The efficacy of the phyllosphere N2-fixing isolates for N-nutritionof host plants was studied by spraying suspensions of the culturesgrown on N-free media on rice and wheat seedlings. In IR-26rice or Sonalika and Janak wheat grown on soil in wooden flatsor earthenware pots, 22 per cent of the 161 cultures studiedcaused increased height and about three-quarters of the culturesenhanced dry weight by more than 50 per cent; chlorophyll andN-contents were enhanced more than 50 per cent by about halfand two-thirds of the cultures respectively. In N-free sandculture 26 of the 50 promising strains doubled N-content, and30 doubled dry weight of the tested plants. In some cases dryweight, number of grains per panicle, and 1000 grain weightwere increased by 300, 7083 and 126158 per centrespectively; N-content of straw and seed was increased three-or fourfold. In several cases the beneficial effects were foundto match closely the performance of plants receiving ammoniumsulphate. Nitrogen-fixing micro-organisms, nitrogen nutrition, phyllosphere, rice, tropical plants, wheat 相似文献
13.
Azetidine-2-carboxylic acid (AZC), which occurs naturally inLiliaceous plants, is reported to be a proline (pro) analoguePlant cell walls contain extensin, which is richin hydroxyproline (hyp). Peptidyl hyp arises through hydroxylationof peptidyl pro followed by glycosylation (arabinose attachment)of hyp Because AZC replaces peptidyl prolyl residues, it maybe a useful tool for evaluating the significance of hyp-o-arabinoselinkages in cell elongation. Therefore, we determined the effectof AZC on [14C]pro uptake, incorporation and conversion to wall-bound[14C]hyp in relation to elongation of lily pollen tubes whosewalls consist, in part, of hyp-containing glycopeptides TheAZC suppressed pollen germination 942 per cent (110mM) and subsequent tube elongation 4054 per cent (0·11mM without affecting respiration In contrast, similar hyp concentrationswere without effect on tube elongation Whereas uptake of [14C]prowas 16·56·2 per cent of the control at0·11 mM AZC, [14C]leucine uptake was 8525per cent of the control. Light microscope radioautography revealedfewer silver grains over tubes elongated in 0·11mM AZC than in its absence. Incorporation of [14C]pro into tnchloroaceticacid (TCA)-precipitable cytoplasm was reduced by only 10 percent at 0·011 mM but 43 per cent at 10 mM AZCGel filtration of cytoplasm from pollen germinated without AZCbut with [14C]pro resulted in labelled void volume (V) and threeretarded peaks (RIIII) Incorporation into V and RI wasinhibited at both 0·01 and 1 mM AZC These AZC concentrationsreduced conversion of [14C]pro to wall-bound hyp by 20 percent However, total incorporation of [14C]pro into salt-water-purifiedwall fractions was suppressed 4753 per cent (0·11mM AZC). Lilium longiflorum, lily, hydroxyproline, proline, azetidine-2-carboxylic acid, pollen, pollen tube elongation 相似文献
14.
Elemental analysis (for carbon, hydrogen, nitrogen and sulphur)and ash data for kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A. R. Ferguson var. deliciosa cv. Hayward] stems,leaves and fine roots were used to calculate the specific costs(kg carbohydrate kg-1 dry matter) of organ synthesis with ammoniacalnitrogen supply. Those costs ranged between 1·19 and1·35 for stems and 1·19 and 1·27 for leaves.The mean annual specific cost for fine roots was 1·17.Seasonal vine growth costs were calculated by multiplying thespecific costs by biomass data for a typical vine. Total costof synthesis was 57·2 kg carbohydrate per vine year-1,taking fine root turnover as three times per season. Nitratenitrogen supply increased that cost by 6·6% to 61·0kg carbohydrate per vine year-1. Fruit growth accounted forthe largest proportion of synthetic costs. Vine growth respiration(expressed in terms of carbohydrate equivalents) accounted forapproximately 11·5% of the total cost of synthesis. Maintenancerespiration was estimated to be 5·28, 8·44, 1·90,8·62 and 13·3 kg carbohydrate per organ year-1for stems, leaves, fruit, above-ground perennial componentsand roots, respectively. Total annual cost of growth and maintenancefor a mature vine was 94·7 and 98·5 kg carbohydrateper vine year-1 with ammoniacal and nitrate nitrogen supply,respectively. Both values are similar to an estimate of vinephotosynthesis. Maintenance respiration accounted for approximately40% of the total annual cost of vine growth, regardless of theform of nitrogen supplied. Peak carbohydrate demand was duringthe period from 60 to 160 d after budbreak.Copyright 1995, 1999Academic Press Actinidia deliciosa, kiwifruit, carbon economy, growth respiration, maintenance respiration 相似文献
15.
Examination of the net assimilation rate (E) during the growingseason in arctic regions by a detached-leaf method revealedno differences between species or with soil richness, but showeda reduction of E with exposure to windprobably resultingfrom coolingand a tendency for E to fall towards thelater part of the growing season. E generally lay in the range0·5 to o·8 g./dm.2/week. E for detached leaves ignores respiratory losses in other partsof the plant and is not comparable with E for whole plants;failure to appreciate this confused a previous comparison ofE under arctic and temperate environments. E for detached leavesin temperate summer conditions is normally around 1·1to 1·5 g./dm.2/week. Thus E is reduced in arctic environmentsto about half the value in temperate conditions. This reductionis due mainly to the cold climate. 相似文献
16.
The effect of the leafless mutation (in whichtendrils replace leaflets and the stipules are reduced to avestigial form) upon foliage area, photosynthetic net CO2 uptakepotential, dry matter production and seed yield in Pisum sativumwas studied by comparing two near-isogenic lines of genotypeafafstst and ++++. The mutation is of potential agronomic valuein that it offers improved lodging resistance, crop drying andharvester throughput. In the conventional phenotype the total foliage area of themain axis attained a plateau (456 cm2) at day 56 from seedlingemergence, whereas corresponding values for the leaflessmutant showed a total area of 208 cm2 at day 68 with no indicationof a plateau. The agronomic consequence of this is discussed.During the vegetative phase of the plant the maximum CO2 uptakepotential in the fully expanded conventional leaf was 8·5mg CO2 leaf1 h1 and in the leaflessmutant this value was 7·0 mg CO2 leaf1 h1.For most leaves of the latter phenotype this valuewas between 30 and 60 per cent less than for their conventionalcounterpart. There was a consistently higher photosyntheticpotential per unit area in tendrils of the leaflessmutant than in leaflets of the conventional phenotype. The respectivemean specific values for the two phenotypes were 53 and 37 mgCO2 dm2 h1. The problem of obtaining a meaningfulsurface area value for tendrils is discussed and the cylindricalnature of tendrils is taken into account. The leafless mutant consistently accumulated 50per cent less dry matter than did conventional plants in theperiod from seedling emergence to anthesis and yield of maturedry seed per plant showed a reduction of 50 per cent both inseed number and total seed weight. The implications for future breeding and selection programmesaimed at haulm reduction are discussed in relation to evaluatingthe ability of the background genotype to produce adequate tendrilsin the presence of afafstst. Triticum aestivum, wheat, callus culture, organogenesis 相似文献
17.
The inactivation of nitrate reductase in the leaves and rootsof barley (Hordeum vulgare L. cv. Mazurka) during and afterextracting was investigated. At 0 °C in the absence of casein,25 per cent of total. i.e. maximal in vitro, nitratereductase activity was lost during the 2 min extraction process,followed by a slower loss of activity while the extract wasstored in ice. Activity was maintained by adding a minimum of1 per cent casein to the extraction medium containing 0·1M phosphate (pH 7·5), 1 mM EDTA and 1 mM dithiothreitol.Nitrate reductase was stable for several hours in these extracts,but declined in a first order manner in the absence of dithiothreitol.Casein also prevented the initial loss while making root extracts,but had less effect during storage. Using casein and thiols, nitrate reductase activity in light,(as product of maximal in vitro rates and wt g1) in leaveswas 98 per cent of the total activity in 31-day-old plants grownwith full nutrient in water culture and 60-day-old field-grownplants receiving no fertilizer. Field-grown plants, however,exhibited only 17 per cent of the activity of culture-grownplants. Nitrate reductase in leaves of barley plants grown in waterculture had a diurnal rhythm. During the first 3 h of the lightperiod, activity increased to 1·3 x the darkvalue. This was followed by a temporary decrease and then byanother increase to a maximum of 1·7 x the darkvalue, occurring about 8 h after illumination. Activity thendecreased during the rest of the light period and in darkness. Hordeum vulgare L., barley, nitrate reductase 相似文献
18.
Simultaneous observations on extension growth and respirationrate (oxygen consumption) of 2-mm. sections excised from theextension zone of roots of pea (Pisum sativum) growing in distilledwater and 0·5 per cent. sucrose have yielded resultsclosely similar to those of Brown and Sutcliffe (1950). Respirationrate is not obviously correlated with growth rate either inwater or in sucrose, but it is strongly correlated with sectionlength. Respiration rate per unit section length (¬per unitfresh weight) shows a marked downward drift during extensionand is affected little by growth conditions. Tentative suggestionsare advanced to account for the small differences between driftsin o·5 per cent. sucrose and those in distilled water. Medium agitation produces an immediate and sustained stimulationof growth but no stimulation of oxygen uptake until the latergrowth stages. Thus respiration per unit section length is unaffectedby agitation at any stage. A typical growth response to ß-indolylacetic acid(IAA) was obtained, with a maximum stimulation (of about 35per cent.) at 1 part in 1011 and inhibitions increasing progressivelywith concentration beyond the threshold of about i part in 109.Both percentage stimulation and percentage inhibition of growthwere independent of the presence of sucrose. Respiratory responses to ß-indolylacetic acid werecomplex. In water no immediate response could be detected witheither a growth-stimulatory (1011) or a growth-inhibitory(10-8) concentration, while in 0·5 per cent. sucrosethe inhibitory concentration prevented the small immediate respiratoryrise due to the sucrose, probably by impeding sugar entry. Duringthe subsequent period of rapid growth (up to 36 hours) the smallrespiratory responses observed closely followed the small growthresponses to both concentrations of IAA, suggesting that theformer are the direct result of the differences in section lengthinduced by the auxin. When growth ceases (at 48 hours) sectionswhich have grown considerably in sucrose show respiratory ratesstill closely correlated with section length, whereas in waterboth concentrations of auxin induce marked depressions in respirationrate. It is concluded that ß-indolylacetic acid in bothgrowth-stimulatory and growth- inhibitory concentrations hasno direct effect on the activity of the respiratory enzyme systemof growing root cells. The small respiratory responses are bestexplained as resulting from differential changes in sectionsize and correlated changes in the enzyme complements of thegrowing cell. 相似文献
19.
Investigations of Carbon Transport in Plants: II. THE EFFECTS OF LIGHT AND DARKNESS AND SINK ACTIVITY ON TRANSLOCATION 总被引:4,自引:0,他引:4
The use of 11C as a tracer has allowed repetitive measurementsof the speed of assimilate translocation to be made on singlemaize plants throughout prolonged periods of light and darkness.The speed appeared to double when the light was switched on.The time required to achieve a maximum speed, usually about3·5 cm min1, depended on the duration of the previousdark period. When the plant was transferred to darkness thespeed immediately decreased by about 20 per cent and continuedto decrease over the next 20 h to values of 0·5 to 0·9cm min1. The mean speed of translocation in tomato in the light, andother C3 plants, was usually about 1 cm min1. It wasreduced by 1530 per cent when the fruit was removed orcooled from 26 to 10°C. 相似文献
20.
Carbon dioxide efflux from 5- to 20-day-old pea fruits was measuredfor plants grown in controlled environment at 15 °C and600 µmol s1 m2 photon flux density in a16 h photoperiod. The rate of CO2 output per fruit increasedquickly from 0.005 to 0.018 mg CO2 min1 during fruitelongation and subsequently more slowly to 0.030 mg CO2 min1as the fruits inflated. On a d. wt basis the rate was highest,0.175 mg CO2 g1 min1, in the youngest fruits anddeclined curvilinearly with increasing fruit weight to 0.02mg CO2 g1 min1. Separation of maintenance andgrowth components was achieved by starvation methods and bymultiple regression analysis. From the latter method estimatesof the maintenance coefficient declined hyperbolically from150±8.7 mg carbohydrate g1 d. wt day1 inthe very young fruits (0.05 g) to 10.4±0.36 mg carbohydrateg1 d. wt day1 in older fruits (2.0 g). On a nitrogenbasis maintenance costs decreased from 2240 to 310 mg carbohydrateg1 nitrogen day1 while nitrogen concentrationfell from 6.7 to 3 per cent d. wt. A simple linear relationshipbetween maintenance cost per unit d. wt and nitrogen concentrationwas not observed. A growth coefficient of 50±6.7 mg carbohydrate g1growth (equivalent to a conversion efficiency, YG, of 0.95)was estimated for all fruits examined. The overall efficiency, Y, increased from a mean of 0.70 to0.85 during fruit elongation and subsequently declined to 0.80.For a given fruit weight, efficiency increased asymptoticallywith relative growth rate; both asymptote and slope of the relationshipincreased as the fruits grew. Pisum sativum L., garden pea, legume fruit, carbon dioxide efflux, maintenance respiration, growth respiration 相似文献