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1.
Characterization of C4 Type Leaf Anatomy in Grasses (Poaceae). Mesophyll: Bundle Sheath Area Ratios 总被引:1,自引:0,他引:1
The cross-sectional area of primary carbon assimilation(PCA) (or mesophyll) tissue and of photosynthetic carbonreduction (PCR) (or parenchymatous bundle sheath, PBS)tissue associated with each vein has been measured in transversesections of leaf blades of 124 grass species (Poaceae). Thespecies sample is representative of all major grass taxa, andof all photosynthetic types found in this family, viz. C3, C3/C4intermediate, C4 NADP-malic enzyme type (NADP-ME), C4 NAD-malicenzyme type (NAD-ME) and PEP carboxykinase type (PCK). MeanPCA (or mesophyll) area per vein varies between photosynthetictypes in the order C3 > NAD-ME > PCK = NADP-ME, mean PCR(or PBS) area per vein in the order NAD-ME > PCK = C3 >NADP-ME, and mean PCA/PCR (or mesophyll/PBS) area ratio in theorder C3 > NADP-ME > NAD-ME > PCK. Since grass leaveshave parallel venation, tissue areas and area ratios are directlyproportional to tissue volumes and volume ratios. Regressionanalyses of plots of PCA (or mesophyll) area per vein againstPCR (or PBS) area per vein yield characteristic slopes for photosynthetictypes. Differences between types in all these parameters arenearly always statistically significant, even within high leveltaxonomic groups (Eupanicoids and Chloridoids). However, differencesbetween major taxa (Eupanicoids, Andropogonoids, Chloridoids),within a photosynthetic type, are frequently not significant.This histometric characterization of photosynthetic types isdiscussed in relation to the co-operation of PCA and PCR tissuesin C4 photosynthesis, to possible differences between C4 typesin PCR spatial requirements and to the developmental originof PCR tissue. Grasses, Poaceae, C4 photosynthesis, C4 leaf blade anatomy, Kranz, NADP-malic enzyme, NAD-malic enzyme, PEP carboxykinase, PCA tissue, PCR tissue, taxonomy 相似文献
2.
Woodrow, L. and Grodzinski, B. 1987. Ethylene evolution trombracts and leaves ol Poinsettia, Euphorbia pulcherrima Willd.J.exp. Bot. 38: 20242032. Ethylene release from fully expanded, red and white bracts andleaves of poinsettia, Euphorbia pulcherrima Willd., was compared.On a laminar (area) basis leaves contained about 50 times morechlorophyll and demonstrated 10 times the photosynthetic rateof the bracts. Both tissues contained starch, however, solublecarbohydrate in the bracts consisted primarily of reducing hexoseswhile the leaves contained mainly sucrose for translocation.The total free alpha-amino nitrogen content of the bract tissuewas twice that of the leaf tissue. The leaves contained moreACC (1-aminocyclopropane-1-carboxylic acid) and produced proportionallymore endogenous C2H4 than either the red or white bracts. ACC-stimulated2H4 release was also greatest from the green tissue indicatingthat the EFE (ethylene forming enzyme) was most active in theleaves. The specific activity of the 14C2H4/12C2H4 releasedfrom [2,3-14C]ACC confirmed ACC as the primary precursor ofC2H4 in this tissue. Ethylene release from the non-photosynthetic,bract tissue was not markedly affected by alterations in CO2or light conditions. In green leaf tissue endogeneous ethylenerelease increased from 1·5 to 6·0 pmol C2H4 cm2h1 while ACC-stimulated ethylene release increased from10 to 35 pmol C2H4 cm2 h1 as the CO2 partial pressureincreased from 100 to 1 200 µbar. Key words: Poinsettia, ethylene, bracts 相似文献
3.
Carbon dioxide and water vapour exchanges for single attachedleaves of the temperate C4 grass Spartina townsendii were measuredunder controlled environment conditions in an open gas-exchangesystem. The responses of net photosynthesis, stomatal resistance,and residual resistance to leaf temperature and photon fluxdensity are described. The light and temperature responses ofnet photosynthesis in S. townsendii are compared to informationon these responses in both temperate C3 grasses and sub-tropicalC4 grasses. Adaptation of photosynthesis in this C4 speciesto a cool temperate climate is indicated both by the light andtemperature responses of net photo-synthesis. Unlike the C4grasses examined previously, significant rates of net photosynthesiscan be detected at leaf temperatures below 10?C. Rates of netphotosynthesis equal or exceed those reported for temperateC3 grasses at all of the temperature (540?C) and photonflax density (132500µmol m2 s1) conditionsexamined. Maximum rates of net photosynthesis in S. townsendiiare almost double those reported for C3 herbage grasses. Unliketemperate C3 grasses, the major limitation to net photosynthesisat low leaf temperatures (10?C and below) is the stomatal resistance,showing that the low residual resistance characteristic of C4species is maintained in S. townsendii even at low leaf temperatures. 相似文献
4.
The maximum catalytic activities of several photorespiratoryand photosynthetic enzymes were determined in leaf extractsof three C3C4 intermediates (Alternanthera ficoides,A. tenella and Parthenium hysterophorus) and were compared tothose of C3 (A. sessiles, Pisum sativum) and C4 (A. pungens,Zea mays and Amaranthus hypochondriacus) species. The activitylevels of key photorespiratory enzymes, glycolate oxidase, catalase,NADH-hydroxypyruvate reductase and glycerate kinase were less(28 to 35% reduced) in intermediates than those of typical C3species. Similarly, the activities of photorespiratory aminotransferasesin the C3C4 intermediates were also partially reduced(23 to 37% reduction). The activities of phosphoenolpyruvatecarboxylase (PEPC), pyruvate, orthophosphate dikinase and NAD-malicenzyme were higher (2 to 7 times) in leaf extracts of the intermediatesthan those of C3 species. But the ratios of PEPC/rubisco inthe C3C4 intermediates were more like C3 than C4 species.We draw attention to the partial reduction in enzyme activityof photorespiratory metabolism, which could be an importantfactor for restriction of photorespiration in the C3C4intermediate species, in addition to enzyme compartmentationand/or operation of a C4-like cycle Key words: C3C4 intermediates, C4 pathway, enzyme profile, glycolate metabolism, photorespiration, photosynthesis 相似文献
5.
A Comparison of the Growth of the C4 Grass Spartina anglica with the C3 Grass Lolium perenne at Different Temperatures 总被引:1,自引:0,他引:1
Dunn, R., Thomas, S. M., Keys, A. J. and Long, S. P. 1987. Acomparison of the growth of the C4 grass Spartina anglica withthe C3 grass Lolium perenne at different temperatures.J.exp. Bot. 38: 433441. S. anglica is one of the few C4 species which occurs naturallyin cool temperate zones. It is known to attain photosyntheticrates which equal or exceed those of C3 grasses over the temperaturerange typical of the spring and summer in cool temperate climates.This study examines whether S. anglica can also attain comparablegrowth rates at these temperatures. Seedlings of S. anglicaand L. perenne cv. S23 were grown in controlled environmentsat 10,15,20 and 25 °C. Quantitative growth analysis wasconducted by taking frequent harvests to determine the progressionsof leaf area and plant weight of individual plants with time.Quadratic regressions were found to describe these progressionswell. Instantaneous derived growth parameters were calculatedfrom the fitted regressions. Both absolute and relative growthrates of S. anglica were significantly lower than for L. perenne,this being largely attributable to a lower ratio of leaf areaproduction per unit of plant dry weight. Although the amountof dry matter invested into leaves was similar, the leaf areaper unit of leaf dry weight was lower in S. anglica. In comparisonto L. perenne, the rate of dry matter accumulation per unitof leaf area (ULR) was higher in S. anglica at 25 °C andinitially equal at 10 °C. Prolonged exposure to 10 °Csteadily reduced ULR in S. anglica which approached zero at80 d. Although growth in S. anglica is reduced more by low temperaturethan it is in L. perenne, by comparison to other C4 speciesthe assimilatory capacity of S. anglica is more tolerant oflow temperature exposure. Key words: C4 photosynthesis, temperature, quantitative growth analysis 相似文献
6.
Silica (SiO2.nH2O) is deposited in large quantities in the shootsystems of grasses. In the leaf epidermal system, it is incorporatedinto the cell wall matrix, primarily of outer epidermal walls,and within the lumena of some types of epidermal cells. This biogenic silica can be stained specifically with methylred, crystal violet lactone, and silver amine chromate. At theultrastructural level, the silica in lumens of silica cells,bulliform cells and long epidermal cells is made up of rodsabout 2.5 µm in length and 0.4µm in width. Ultimateparticles in the rods range from 1 to 2 nm in diameter. In contrast,silica in the cell wall matrix of trichomes and outer wallsof long epidermal cells is not rod-shaped, but rather, formsroughly spherical masses. Detailed analyses are presented on the frequencies of occurrenceof the different types of epidermal cells that contain silicain the leaves of representative C3 and C4 grasses. The C4 grasseshave higher frequencies of bulliform cell clusters, silica cells,and long epidermal cells, whereas the C3 grasses have higherfrequencies of trichomes. No correlation was found in the frequencyof occurrence of silica bodies in bulliform cells for C3 grassesas compared with C4 grasses. Of all the grasses examined, Coix,Oryza, and Eleusine had the highest densities of such bodies,and some taxa had no silica bodies apparent in their bulliformcells. The idea that silica bodies in bulliform cells and silica cellsmight act as "windows and trichomes might function aslight pipes to facilitate light transmission throughthe epidermal system to photosynthetic mesophyll tissue belowwas tested. The experimental data presented do not support eitherof these hypotheses. C2 and C4 grasses, biogenic silica, light pipes, window hypothesis, silica staining, silica ultrastructure 相似文献
7.
Plant allometry, leaf nitrogen and phosphorus stoichiometry, and interspecific trends in annual growth rates 总被引:8,自引:0,他引:8
Niklas KJ 《Annals of botany》2006,97(2):155-163
Background Life forms as diverse as unicellular algae,zooplankton, vascular plants, and mammals appear to obey quarter-powerscaling rules. Among the most famous of these rules is Kleiber's(i.e. basal metabolic rates scale as the three-quarters powerof body mass), which has a botanical analogue (i.e. annual plantgrowth rates scale as the three-quarters power of total bodymass). Numerous theories have tried to explain why these rulesexist, but each has been heavily criticized either on conceptualor empirical grounds. N,P-Stoichiometry Recent models predicting growth rateson the basis of how total cell, tissue, or organism nitrogenand phosphorus are allocated, respectively, to protein and rRNAcontents may provide the answer, particularly in light of theobservation that annual plant growth rates scale linearly withrespect to standing leaf mass and that total leaf mass scalesisometrically with respect to nitrogen but as the three-quarterspower of leaf phosphorus. For example, when these relationshipsare juxtaposed with other allometric trends, a simple N,P-stoichiometricmodel successfully predicts the relative growth rates of 131diverse C3 and C4 species. Conclusions The melding of allometric and N,P-stoichiometrictheoretical insights provides a robust modelling approach thatconceptually links the subcellular machinery ofprotein/ribosomal metabolism to observed growth rates of uni-and multicellular organisms. Because the operation of this machineryis basic to the biology of all life forms, its allometry mayprovide a mechanistic explanation for the apparent ubiquityof quarter-power scaling rules. 相似文献
8.
Stomatal Responses of Variegated Leaves to CO2 Enrichment 总被引:1,自引:0,他引:1
The responses of stomatal density and stomatal index of fivespecies of ornamental plants with variegated leaves grown attwo mole fractions of atmospheric CO2 (350 and 700 µmolmol-1) were measured. The use of variegated leaves allowed anypotential effects of mesophyll photosynthetic capacity to beuncoupled from the responses of stomatal density to changesin atmospheric CO2 concentration. There was a decrease in stomataldensity and stomatal index with CO2 enrichment on both white(unpigmented) and green (pigmented) leaf areas. A similar responseof stomatal density and index was also observed on areas ofleaves with pigmentation other than green indicating that anydifferences in metabolic processes associated with colouredleaves are not influencing the responses of stomatal densityto CO2 concentrations. Therefore the carboxylation capacityof mesophyll tissue has no direct influence on stomatal densityand index responses as suggested previously (Friend and Woodward1990 Advances in Ecological Research 20: 59-124), instead theresponses were related to leaf structure. The stomatal characteristics(density and index) of homobaric variegated leaves showed agreater sensitivity to CO2 on green portions, whereas heterobaricleaves showed a greater sensitivity on white areas. These resultsprovide evidence that leaf structure may play an important rolein determining the magnitude of stomatal density and index responsesto CO2 concentrations.Copyright 1995, 1999 Academic Press Leaf structure, photosynthesis, stomatal conductance, CO2, stomatal density, stomatal index 相似文献
9.
Silica Deposition in Some C3 and C4 Species of Grasses, Sedges and Composites in the USA 总被引:2,自引:0,他引:2
We report new information on silica deposition in 15 plant species,including nine grasses, two sedges and four composites. Thesilica depositional patterns found in seven of the grass speciesindicate that they are C4 plants. However the festucoid grassCortaderia selloana is a C3 plant with long leaf trichomes andoval silica structures in the leaves. In contrast the panicoidC4 grasses Chasmathium latifolium, Chasmathium sessiflorum,Imperata cylindrica, Panicum repens, Panicum commutatum andSetaria magna, all produce dumb-bell-shaped silica structuresin the leaves. The chloridoid grasses Spartina patens and Spartinacynosuroides have saddle-shaped structures and no dumb-bellor oval shaped ones. The sedges Rhynchospora plumosa and Scirpuscyperinus were found to have oval phytoliths and may be C3 plants.Our examination of these and other grasses strongly suggeststhat C4 grasses tend to produce the same type of silica cells.Grasses and sedges with C3 type photosynthesis tend to produceoval silica structures. The composite Grindelia squarrosa andsunflowers Helianthus angustifolia, Helianthus atrorubens andHelianthus tuberosus absorb relatively small amounts of siliconand larger amounts of calcium, where both elements deposit inleaf trichomes. We found no clear indicator for the C3 sunflowersor C4 types in the Asteraceae. Helianthus tuberosus leaves havemany trichomes on the adaxial surface. These trichomes havea higher concentration of silica than the surrounding leaf surface.Helianthus tuberosus leaves had much higher ash and silica contentsthan those of Helianthus angustifolia and Helianthus atrorubens.The composite Grindelia squarrosa has a usual deposition ofsilica in the basal cells around the guard cells. Silica depositionoften reflects the surface features of a leaf. An exceptionis Scripus cyperinus where the silica structures are deep inthe tissue and do not reflect the surface configurations. Theinforescence of Setaria magna had a 14.64 silica content. Thetufts of white, silky hairs characteristic of Imperata cylindricainflorescence have no silica. C3 and C4 plants, silica and ash content, scanning electron microscopy, energy-dispersive X-ray analysis, silicon distribution, spectra of elements in plants, trichomes, silica fibres, phytoliths 相似文献
10.
KARGIOLAKI HARIKLIA; OSBORNE DAPHNE J.; THOMPSON FRANK B. 《Journal of experimental botany》1991,42(9):1189-1198
Differences in premature leaf abscission and in visible steminjury in genetic lines of poplar followed continuous fumigationswith air pollutant levels of SO2 (90100 nl l1)and O3 (7080 nl l1) either separately or together.The clones used were: Populus deltoides var. missiouriensisMarsh., P. nigra cv. italicd L., and the hybridsP. nigra cv. italica xP. deltoides (He-X/3) andP. nigra cv.italica x P. nigra cv. Serres(He-K/7). While most leaf abscission occurred within 20 d fromthe start of fumigation, stem lesions (intumescences), appearedonly after 72 d. Their anatomical characteristics include theformation of lysigenous aerenchyma in the lower parts of theintumescence, the sloughing of superficial cells from the injuredarea, and the development of crystalline formations on the surfaceof the lesions. P. deltoides exhibited the least morphologicalresponse to the gases. Ethylene released from fumigated leaves was determined at thesame gas concentration of SO2 (100 nl l1), O3 (75 nll1) and their mixture. Leaves of P. deltoides consistentlyshowed the lowest ethylene production after the gas treatments.P. italica production was higher but was littlealtered by the treatments. The two hybrids He-X/3 and He-K/7showed the greatest increases in ethylene evolution with time.With He-K/7 exposed to the gas mixture the production of ethylenedecreased after the initial sharp rise during days 12,and reflected the considerable leaf damage observed after day3. The results suggest that sensitivity to air pollution, (as shownby leaf abscission and the formation of stem intumescences)can be correlated with the level of pollutant-induced ethyleneevolution from leaves. Initially high levels could induce abscission,whilst prolonged production could be responsible for intumescenceinitiation. The discussion proposes a series of events fromSO2 and/or O3 entry into the leaf and the physiological reasonsfor the clonal differences. Key words: Sulphur dioxide, ozone, ethylene, poplar, leaf abscission, stem lesions 相似文献
11.
A model is presented for growth of individual and successivemain-stem leaves of cotton, based on a series of indoor experimentsand data sets from the literature. Three variable parametersare used to describe individual leaf growth: relative growthrate of meristematic tissue (R1), relative rate of approachof final area (R2) and a position parameter (t0.5)which governs the transition from meristematic to extensiongrowth. Final area of a leaf does not occur in the model asa deterministic quantity but it is a result of the processesduring growth. The model generates successive mainstem leavesand sympodial leaves as an integrated system. Assimilate shortagesoccurring in the plant operate on R1 leading to the characteristicchange of final leaf area along the mainstem. Gossypium hirsutumL., cotton, leaf growth, relative growth rate, meristematic tissue, extension growth, mathematical model 相似文献
12.
ROMERO-ARANDA R.; BONDADA B. R.; SYVERTSEN J. P.; GROSSER J. W. 《Annals of botany》1997,79(2):153-160
The effect of tetraploidy on leaf characteristics and net gasexchange was studied in diploid (2x ) and autotetraploid (4x) Valencia sweet orange (Citrus sinensis (L.)Osb.) and Femminello lemon (Citrus limon (L.)Burm. f.) leaves. Comparisons between ploidy levels were madeunder high irradiance (I) in a growth chamber or low total Iin a glasshouse. Tetraploids of both species had thicker leaves,larger mesophyll cell volume and lower light transmittance thandiploids regardless of growth I. Mesophyll surface area perunit leaf area of 2x leaves was 515% greater than on4x leaves. Leaf thickness and mesophyll cell volume were greaterin high I leaves than low I leaves. In high I, average leafarea was similar for 2x and 4x leaves, whereas in low I it was30% greater in 4x than in 2x leaves. Nitrogen and chlorophyllconcentration per cell increased with ploidy level in both growthconditions. The ratio of chlorophyll a:b was 25% greater in2x than in 4x leaves. When net CO2assimilation rate (ACO2) wasbased on leaf area, 4x orange leaves had 2435% lowerACO2than their diploids. There were no significant differencesin ACO2between 2x and 4x orange or lemon leaves when expressedon a per cell basis. Overall, lower ACO2per unit leaf area oftetraploids was related to increase in leaf thickness, largermesophyll cell volume, the decrease in mesophyll area exposedto internal air spaces, and the lower ratio between cell surfaceto cell volume. Such changes probably increased the resistanceto CO2diffusion to the site of carboyxlation in the chloroplasts. Cell volume; chlorophyll; irradiance; leaf thickness; nitrogen; photosynthesis; ploidy; Citrus limon ; C. sinensis ; Valencia sweet orange; Femminello lemon 相似文献
13.
Effect of Elevated CO2 on Stomatal Density and Distribution in a C4 Grass and a C3 Forb under Field Conditions 总被引:1,自引:0,他引:1
Knapp Alan K.; Cocke Meagan; Hamerlynck Erik P.; Owensby Clenton E. 《Annals of botany》1994,74(6):595-599
Two common tallgrass prairie species, Andropogon gerardii, thedominant C4 grass in this North American grassland, and Salviapitcheri, a C3 forb, were exposed to ambient and elevated (twiceambient) CO2 within open-top chambers throughout the 1993 growingseason. After full canopy development, stomatal density on abaxialand adaxial surfaces, guard cell length and specific leaf mass(SLM; mg cm-2) were determined for plants in the chambers aswell as in adjacent unchambered plots. Record high rainfallamounts during the 1993 growing season minimized water stressin these plants (leaf xylem pressure potential was usually >-1·5 MPa in A. gerardii) and also minimized differencesin water status among treatments. In A. gerardii, stomatal densitywas significantly higher (190 ± 7 mm-2; mean ±s.e.) in plants grown outside of the chambers compared to plantsthat developed inside the ambient CO2 chambers (161 ±5 mm-2). Thus, there was a significant 'chamber effect' on stomataldensity. At elevated levels of CO2, stomatal density was evenlower (P < 0·05; 121 ± 5 mm-2). Most stomatawere on abaxial leaf surfaces in this grass, but the ratio ofadaxial to abaxial stomatal density was greater at elevatedlevels of CO2. In S. pitcheri, stomatal density was also significantlylower when plants were grown in the open-top chambers (235 ±10 mm-2 outside vs. 140 ± 6 mm-2 in the ambient CO2 chamber).However, stomatal density was greater at elevated CO2 (218 ±12 mm-2) compared to plants from the ambient CO2 chamber. Theratio of stomata on adaxial vs. abaxial surfaces did not varysignificantly in this herb. Guard cell lengths were not significantlyaffected by growth in the chambers or by elevated CO2 for eitherspecies. Growth within the chambers resulted in lower SLM inS. pitcheri, but CO2 concentration had no effect. In A. gerardii,SLM was lower at elevated CO2. These results indicate that stomataland leaf responses to elevated CO2 are species specific, andreinforce the need to assess chamber effects along with treatmenteffects (CO2) when using open-top chambers.Copyright 1994, 1999Academic Press Andropogon gerardii, elevated CO2, Salvia pitcheri, stomatal density, tallgrass prairie 相似文献
14.
Removal of the blade from the leaf subtending the first flowerbud on Cyclamen persicum Swan Lake plants causedthe petiole of that leaf to senesce, but had no effect on thegrowth of the flower peduncle in the debladed petiole's axil.A 10 mg NAA l1 application generally had no effect onpetiole senescence, peduncle elongation or flowering date whenapplied to the cut end of the petiole after blade removal. A25 mg GA3 l1 application or a combination of 25 mg GA3l1 application or a combination of 25 mg GA3 l1plus 10 mg NAA l1 delayed petiole senescence and enhancedpeduncle elongation and subsequent flowering. No treatment significantlyaltered peduncle length at the time of flowering. Cyclamen persicum Mill, Swan Lake, tissue receptivity, flowering, GA3, NAA 相似文献
15.
Anatomical and morphological structures of leaf blades werecompared between C3 and C4 species in Panicum. Inter-specificvariation of stomatal density, longitudinal vein density andmesophyll thickness was highly correlative either plus or minuswithin respective groups. The two groups could not be distinguishedby a single character, since the variation ranges overlappedeach other. However, the quantitative relations between veindensity and the other two characters differentiated the twogroups well. In C3, stomatal density seemed to be a primaryfactor for regulating water balance, while in C4 vein systemwas considered to be important for the regulation. The specieswith intermediate photosynthesis behaved similar to the C3 species.In the C3 group, correlative variation was observed betweenleaf width, leaf angle and the three characters mentioned above.Variation of light-receiving area due to the changes of widthand angle of leaf blades was considered to be one of the adaptivestrategies of this group. Increase of light-receiving area wasin connection with the thinning of leaves. On the other hand,in the C4 correlations between length, width and angle of leaveswere low. Such loose character correlation may be achieved byits efficiency of CO2 utilization and its well developed veinsystems. Besides, NAD-me type species tended to have relativelylower stomatal and vein densities as compared with the otherdecarboxylation types in this group. Panicum, photosynthesis, C3, C4, decarboxylation types, leaf, stomata, vein 相似文献
16.
17.
《Journal of experimental botany》1977,28(6):1247
Effects of coupled solute and water flow in plant roots withspecial reference to Brouwer's experiment. Edwin L. Fiscus. p. 71 Abstract: Line 3 delete interval insertinternal. p. 73 Materials and Methods: line 6: delete diversion insert division line 9 equation should read Jv=Lp PRT(C0C1). 74 Last line of figure legend: 101 should read 1011. 75 Line 11: delete seems insert seem. le 1 column heading106 should read 1011. 77 delete ...membrane in series of... insert membranein series or... Delete final paragraph. 相似文献
18.
When grown in pots and well-watered, the relative growth ratesof the above ground parts of two species of Moricandia (M. arvensis,an intermediate C3C4 species, and M. moricandioides,a C3 species) were inferior to those of two cultivated Brassicaspecies (B. campestris and B. napus). The Moricandia specieshad thicker leaves (greater d.wt per unit leaf area) with morechlorophyll than the Brassica species and had slightly greaterrates of photosynthesis per unit leaf area at an irradiance(400700 nm) of 2000 µmol quanta m2 s 1.Leaves of M. arvensis, known to have a CO2 compensation pointbetween that of C3 and C4 species, had a lower ratio of theintercellular to atmospheric partial pressure of CO2 (C1/Ca)and a greater instantaneous water use efficiency (WUE) thanthose of M. moricandioides and the Brassica species. Carbon isotope discrimination ( 相似文献
19.
The ontogenic changes in several component processes of photosynthesiswere measured in chickpeas. Gas exchange characteristics ofintact leaves were studied to analyse the effects of ambientconditions under which chickpeas are usually grown. The CO2assimilation rate per unit leaf area remained fairly high duringthe vegetative stage, reaching a peak at early pod-fill anddeclining subsequently throughout pod development. The intercellularCO2 partial pressure (C1) remained more or less constant (195µbar) during vegetative growth and the early stages ofseed-filling. With falling RWC and PAR interception, the stomatalconductance declined more rapidly than the CO2 assimilationrate resulting in a value of C1 less than that normally existingunder ambient conditions. From the A/C1-analysis, CO2 assimilationduring pod-filling appears to be limited by the RuBP-regenerationcapacity because the carboxylation efficiency and in vitro RuBPCaseactivity were initially unaffected. However, as leaves aged,the carboxylation efficiency and in vitro RuBPCase activitydecreased abruptly with increasing leaf temperatures above 30°C, and the C1 was greater than normally existing values(195 µbar), suggesting an increased mesophyll limitationof photosynthesis. It is suggested that a decline in the CO2assimilation rate of leaves during pod development and an acceleratedsenescence are induced by adverse ambient conditions, particularlyplant water stress and high leaf temperature. Key words: Cicer arietinum L., gas exchange, photosynthesis, ribulose-1,5-bisphosphate carboxylase 相似文献
20.
Background and Aims: The grass Alloteropsis semialata is the only plant species withboth C3 and C4 subspecies. It therefore offers excellent potentialas a model system for investigating the genetics, physiologyand ecological significance of the C4 photosynthetic pathway.Here, a molecular phylogeny of the genus Alloteropsis is constructedto: (a) confirm the close relationship between the C3 and C4subspecies of A. semialata; and (b) infer evolutionary relationshipsbetween species within the Alloteropsis genus. Methods: The chloroplast gene ndhF was sequenced from 12 individuals,representing both subspecies of A. semialata and all four ofthe other species in the genus. ndhF sequences were added tothose previously sequenced from the Panicoideae, and used toconstruct a phylogenetic tree. Key Results: The phylogeny confirms that the two subspecies of A. semialataare among the most recently diverging lineages of C3 and C4taxa currently recognized within the Panicoideae. Furthermore,the position of the C3 subspecies of A. semialata within theAlloteropsis genus is consistent with the hypothesis that itsphysiology represents a reversion from C4 photosynthesis. Thedata point to a similar evolutionary event in the Panicum stenodes–P.caricoides–P. mertensii clade. The Alloteropsis genusis monophyletic and occurs in a clade with remarkable diversityof photosynthetic biochemistry and leaf anatomy. Conclusions: These results confirm the utility of A. semialata as a modelsystem for investigating C3 and C4 physiology, and provide moleculardata that are consistent with reversions from C4 to C3 photosynthesisin two separate clades. It is suggested that further phylogeneticand functional investigations of the Alloteropsis genus andclosely related taxa are likely to shed new light on the mechanismsand intermediate stages underlying photosynthetic pathway evolution. 相似文献