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1.
Two pairs of awned and awnless near-isogenic lines of winter wheat were used in a field study in which canopy enclosure apparatus and carbon-14 dosing were employed to assess the contribution of the awns to photosynthesis and grain yield. Awns contributed an average of 12-2% to canopy gross photosynthesis but did not increase the net photosynthesis of the complete canopy. The presence of awns decreased photosynthesis in the remaining ear structures and in the flag and penultimate leaf laminae. Seven days after dosing during the phase of rapid grain filling, 80% of the carbon recovered was located in the grains. The awns intercepted 9% of the incident visible radiation when fully green, and senesced at similar rates as the ears and flag leaves. In a second experiment the effect of awns on grain yield and its components was investigated in crosses segregating for height and presence of awns. Awns did not increase grain yields in either experiment. It appears that for British conditions in the absence of severe drought there is little advantage to be gained at present by breeding awned varieties of wheat. 相似文献
2.
Effect of awns and drought on the supply of photosynthate and its distribution within wheat ears 总被引:2,自引:0,他引:2
L. T. EVANS J. BINGHAM P. JACKSON JENNIFER SUTHERLAND 《The Annals of applied biology》1972,70(1):67-76
The presence of awns doubled the net photosynthetic rate of wheat ears and also increased the proportion of 14CO2 assimilated by the ear that moved to the grain. The effect of water supply on photosynthesis and movement of assimilates was greater for leaves than ears, so that drought increased the proportion of assimilate contributed by ear photosynthesis to grain filling from 13% to 24% in the awnless ears, and from 34% to 43% in the awned ears. 14C assimilated by the ears was most important to the economy of the upper spikelets and to the distal florets in each spikelet, whereas flag leaf assimilate went mainly to the spikelets in the lower half of the ear, and to the proximal florets. Awns increased grain yield in the dry but not in the irrigated treatment, despite the large contribution of awned ears to grain filling. Either the supply of assimilate did not limit grain yield when water supply was not limiting, or there were compensating disadvantages to awns. However, they did not seem to have any adverse effect on the development of the upper florets, nor did they reduce grain number per ear. 相似文献
3.
P. RUCKENBAUER 《The Annals of applied biology》1975,79(3):351-359
The rates of photosynthesis and patterns of translocation of 14C from the flag leaves of tall and semi-dwarf wheat varieties, with and without awns, were compared in a field experiment. The rates of photosynthesis of the awnless varieties fell during the 14 days after anthesis but those of the awned varieties did not change. Wide differences in translocation pattern of 14C supplied at anthesis were also found between varieties, but the differences in distribution pattern of 14C supplied 14 days later were less. At anthesis, the high yielding semi-dwarf selection translocated most carbohydrate to the ears and awned selections least. It is suggested that varietal differences in translocation pattern are determined by differences in the capacity of the grain to store carbohydrate. 相似文献
4.
Ear photosynthesis, carbon isotope discrimination and the contribution of respiratory CO2 to differences in grain mass in durum wheat 总被引:2,自引:2,他引:0
J. L. ARAUS H. R. BROWN A. FEBRERO J. BORT M. D. SERRET 《Plant, cell & environment》1993,16(4):383-392
The role of ear photosynthesis in grain filling was studied in a number of durum wheat (Triticum turgidum var durum L.) landraces and varieties from the Middle East, North Africa, and from the collections of ‘Institut National de la Recherche Agronomique’ (INRA, France) and ‘Centro International de Mejora de Maiz y Trigo’ (CIMMYT, Mexico). Plants were grown in the field in a Mediterranean climate. Flag leaves (blade plus sheath) and ears were kept in the dark from 1 week after anthesis to maturity which reduced grain weight by 22.4% and 59.0%, respectively. In a further experiment, the carbon isotope discrimination ratio (Δ) of ear bracts, awns and flag leaves was measured on samples taken at anthesis and on mature kernels. The mean value of Δ for the water soluble fraction of bracts (17.0‰) and awns (17.7‰) were lower than those of leaves (19.5‰) and fairly similar to those of kernels (17.4‰) averaged across all genotypes. Data indicate that most of the photosynthates in the grain come from ear parts and not from flag leaves. In addition, a higher water use efficiency (WUE) of ear parts than of the flag leaf is suggested by their lower Δ values. Gas exchange in ears and flag leaves was measured during grain filling. Averaged over all genotypes, CO2 diffusive conductance was about five times higher in the flag leaf than in the spike (with distal portions of awns outside the photosynthetic chamber) 2 weeks after anthesis. In absolute terms, the dark respiration rate (Rd) was greater than the net photosynthesis rate (Pn) by a factor of 1.74 in the spike, whereas Rd was much smaller, only 22.1, 65.7 and 24.8% of Pn in blade, sheath and awns, respectively. Data indicate that photosynthesis, and hence the water use efficiency (photosynthesis/transpiration), is greatly underestimated in ears because of the high rates of respiration which diminish the measured rates of net CO2 exchange. Results of 13C discrimination and gas exchange show that genotypes from North Africa have higher WUE than those from the Middle East. The high Rd values of ears as well as their low diffusive conductance suggest that CO2 from respiration may be used as source of carbon for ear photosynthesis. In the same way, the anatomy of glumes, for example, supports the role of bracts using internal CO2 as source of photosynthesis. In the first experiment, the Δ in mature grains from culms with darkened ears compared with control culms provided further evidence in support of this hypothesis. Thus, the Δ from kernels of control plants was 0.40 higher than that from ear-darkened plants, probably because of some degree of refixation (recycling) of respired CO2 in the grains. 相似文献
5.
Carbon exchange rate (CER) and transpiration were measured inflag leaves, whole ears, glumes (referring to the total areaof glumes and lemmas) and awns, in six hexaploid spring wheats(Triticum aestivum L.), three cultivated tetraploid spring wheats(T. turgidum L.), four wild tetraploid wheats (T. dicoccoides),eight six-rowed barleys (Hordeum vulgare L.) and five two-rowedbarleys (H. vulgare L.). Differences between varieties and between species in total earCER and transpiration were associated largely with differencesin ear surface area rather than with rates per unit area. Ratesof CER and transpiration per unit area of ears were 4080%of those of flag leaves, depending on the species. However, since ear surface area was greater than flag leaf areaby a factor of 1.1, 3.9, 5.5 and 4.4, in hexaploid wheat, tetraploidwheat, six-rowed barley, and two-rowed barley, respectively,total ear CER reached up to 90% of that of the flag leaf. The contribution of awns to total ear CER depended largely ontotal awn surface area per ear, rather than on CER per unitawn area. Awns contributed about 4080% of total spikeCER, depending on the species, but only 1020% of spiketranspiration. The disproportionately small contribution ofawns to ear transpiration was caused by the very low rate oftranspiration per unit area of awns. Thus, while transpirationratio (CER/transpiration) was about the same in flag leavesand glumes, it was higher by several orders of magnitude inthe awns. A large amount of awns in the ear is therefore a drought adaptiveattribute in these cereals, for which tetraploid wheat exceededhexaploid wheat and six-rowed barley exceeded two-rowed barley. Key words: Carbon exchange rate, Transpiration, Barley, Wheat 相似文献
6.
Trehalose metabolism in root nodules of the model legume Lotus japonicus in response to salt stress 总被引:1,自引:0,他引:1
Miguel López Jose A. Herrera-Cervera Carmen Lluch Noel A. Tejera 《Physiologia plantarum》2006,128(4):701-709
In wheat ( Triticum aestivum L), the leaves particularly flag leaves have been considered to be the key organs contributing to higher yields, whereas awns have been considered subsidiary organs. Compared with extensive investigations on the assimilation contribution of leaves, the photosynthetic characteristics of awns have not been well studied. In this study, we investigated the ultrastructure of chloroplasts, oxygen evolution, and phosphoenolpyruvate carboxylase [phosphoenolpyruvate carboxylase (PEPCase) EC 4.1.1.31)] activity in both flag leaves and awns during the ontogenesis of wheat. Transmission electron microscope observations showed initial increases in the sizes of grana and the degree of granum stacks from the florescence-emergence stage both in flag leaves and in awns, followed by the breakdown of membrane systems after the milk-development stage. The results of oxygen evolution assays revealed that in both organs, the rate of photosynthesis increased in the first few stages and then decreased, but the decrease occurred much earlier in flag leaves than in awns. A PEPCase activity assay demonstrated that the activity of PEPCase was much higher in awns than in flag leaves throughout ontogeny; the value was particularly high at the late stages of grain filling. Our results suggest that awns play a dominant role in contributing to large grains and a high grain yield in awned wheat cultivars, particularly during the grain-filling stages. 相似文献
7.
Ear of durum wheat under water stress: water relations and photosynthetic metabolism 总被引:3,自引:0,他引:3
The photosynthetic characteristics of the ear and flag leaf of well-watered (WW) and water-stressed (WS) durum wheat (Triticum turgidum L. var. durum) were studied in plants grown under greenhouse and Mediterranean field conditions. Gas exchange measurements simultaneously with modulated chlorophyll fluorescence were used to study the response of the ear and flag leaf to CO2 and O2 during photosynthesis. C4 metabolism was identified by assessing the sensitivity of photosynthetic rate and electron transport to oxygen. The presence of CAM metabolism was assessed by measuring daily patterns of stomatal conductance and net CO2 assimilation. In addition, the histological distribution of Rubisco protein in the ear parts was studied by immunocytochemical localisation. Relative water content (RWC) and osmotic adjustment (osmotic potential at full turgor) were also measured in these organs. Oxygen sensitivity of the assimilation rate and electron transport, the lack of Rubisco compartmentalisation in the mesophyll tissues and the gas-exchange pattern at night indicated that neither C4 nor CAM metabolism occurs in the ear of WW or WS plants. Nevertheless, photosynthetic activity of the flag leaf was more affected by WS conditions than that of the ear, under both growing conditions. The lower sensitivity under water stress of the ear than of the flag leaf was linked to higher RWC and osmotic adjustment in the ear bracts and awns. We demonstrate that the better performance of the ear under water stress (compared to the flag leaf) is not related to C4 or CAM photosynthesis. Rather, drought tolerance of the ear is explained by its higher RWC in drought. Osmotic adjustment and xeromorphic traits of ear parts may be responsible. 相似文献
8.
There is continuing controversy over whether a degree of C4 photosynthetic metabolism exists in ears of C3 cereals. In this context, CO2 exchange and the initial products of photosynthesis were examined in flag leaf blades and various ear parts of two durum wheat (Triticum durum Desf.) and two six-rowed barley (Hordeum vulgare L.) cultivars. Three weeks after anthesis, the CO2 compensation concentration at 210 mmol mol?1 O2 in durum wheat and barley ear parts was similar to or greater than that in flag leaves. The O2 dependence of the CO2 compensation concentration in durum wheat ear parts, as well as in the flag leaf blade, was linear, as expected for C3 photosynthesis. In a complementary experiment, intact and attached ears and flag leaf blades of barley and durum wheat were radio-labelled with 14CO2 during a 10s pulse, and the initial products of fixation were studied in various parts of the ears (awns, glumes, inner bracts and grains) and in the flag leaf blade. All tissues assimilated CO2 mainly by the Calvin (C3) cycle, with little fixation of 14CO2 into the C4 acids malate and aspartate (about 10% or less). These collective data support the conclusion that in the ear parts of these C3 cereals C4 photosynthetic metabolism is nil. 相似文献
9.
Six genotypes of awned spring wheat were more resistant to Sitobion avenae than de-awned wheat. Aphids that fed on awns were up to 22% less fecund and were more likely to be dislodged than aphids that fed elsewhere on an ear. These two factors reduced aphid population growth on awned earing plants in the field to a third of that observed on awnless plants. As awns may also benefit yield and are easy to select for it is recommended that awned winter wheats could be bred and used to reduce the incidence of outbreaks of S. avenae. 相似文献
10.
The Effect of Heat Stress on Wheat Leaf and Ear Photosynthesis 总被引:2,自引:0,他引:2
The effect of heat-hardening on carbon exchange rate per unitarea (CER) of flag leaves, whole ears, and ears with the awnsremoved, was measured in hexaploid (Triticum aestivum L.) andtetraploid (T. turgidum L. and T. dicoccoides) wheat varieties.The CER for awns was calculated by the difference. For the non-hardened hexaploid cv. H-895 the CERfor the leaves and glumes had an optimum temperature of 25°C.By contrast, the CER for the awns increased from 25°C to32°C, indicating an optimum at 32°C or more. Heat-hardeningdecreased the CER of leaves and glumes at the optimum temperature,but increased the CER especially in leaves at supra-optimaltemperatures. Thus, leaf CER in hardened plants became essentiallyindependent of temperatures between 25°C and 32°C. AwnCER was little affected by heat-hardening. For all 12 varieties, leaf and ear CER was smaller in hardenedplants at 30°C than in non-hardened plants at 22°C.Leaf and ear CER measured at 30°C differed significantlybetween varieties within a species. Whole ear CER at 30°Cwas negative in most varieties although the calculated valuefor the awns was positive. Thus, the high temperature optimumfor CER of the awns was a major factor in the variation amongwheat varieties in tolerance of ear CER to heat. The biochemicalattributes of the photosynthetic mechanism in awns responsiblefor the high temperature optimum were already present in wildtetraploid wheat. There was a positive correlation across allvarieties between ear CER at 30°C and the percentage ofawns in total ear area (r = 0930, P = 0 This together with previousresults (Blum, 1985a), suggests that a large amount of awnsin the ear is a sensible selection index in wheat for improvedproduction in hot, dry environments. Key words: Carbon exchange rate, photosynthesis, awns, heat, stress, wheat, breeding 相似文献
11.
Wheat grain yield production in the rain-fed areas is limited by water deficits during crop growth. A greenhouse experiment
was conducted during spring 1992 at ICARDA, Tel Hadya, Syria, with eight genotypes representing two Triticum species (Triticum turgidum var. durum and Triticum aestivum L.) under four soil-moisture regimes (95%, 75%, 55%, and 35% field capacity) to study the effect of water deficit on leaf
development. The phyllochron was similar in the two species across the watering regimes. The range in variation in phyllochron
among the genotypes was similar in the two species. Phyllochron response to water stress among genotypes was distinct in the
driest regime in both species. Cham 6 (T. aestivum) and Gallareta (T. turgidum var. durum) had similar phyllochron across all moisture regimes whereas in other genotypes phyllochron was higher in the dries regime.
Leaf area decreased with increasing moisture stress. Triticum turgidum var. durum genotypes were later in flowering as they had, on average, one leaf more than Triticum aestivum genotypes with similar leaf appearance rates. 相似文献
12.
The gas exchange of barley ears and awns was measured in the field using a gas analysis system and a diffusion porometer. Awn stomatal resistance decreased with increasing irradiance but to a smaller extent than leaf stomatal resistance. Measurements on ears immediately before and after successively removing awns showed that awn transpiration and photosynthesis were proportional to awn area and that awns accounted for 73% of transpiration by the ear. Although the maximum rates of photosynthesis of which awns were capable declined with age, awns accounted for 80–115% of the net CO2 uptake of complete ears because the ears-less-awns could respire more CO2 than they absorbed. Ear photosynthesis accounted for 52% of the weekly increment in ear dry weight after ear emergence, but 5 weeks later photosynthesis by the ear balanced respiration. Overall photosynthesis by the ear accounted for 35 % of its final weight. Differences in the light response curves of leaves and ears can be fully accounted for by the different relationships between stomatal resistance and irradiance of the two organs. 相似文献
13.
Effect of assimilate utilization on photosynthetic rate in wheat 总被引:7,自引:0,他引:7
Summary Two weeks after anthesis, when the grain is filling rapidly, the rate of photosynthesis by flag leaves of wheat cv. Gabo was between 20 and 30 mg CO2 dm-2 leaf surface hour-1 under the conditions used. About 45% of flag-leaf assimilates were translocated to the ear, and only about 12% to the roots and young shoots.On removing the ear, net photosynthesis by the flag leaves was reduced by about 50% within 3–15 hours, and there was a marked reduction in the outflow of 14C-labelled assimilates from the flag leaves.Subsequent darkening of all other leaves on plants without ears led to recovery of flag-leaf photosynthesis, as measured by gas analysis and 14CO2 fixation, and to increased translocation of assimilates to the roots and young shoots. Minor changes in the rates of dark respiration accompanied these major, reversible changes in photosynthetic rate.After more than a week in continuous, high-intensity light, the rate of photosynthesis by flag leaves of intact plants had fallen considerably, but could be restored again by a period in darkness, or by inhibiting photosynthesis in the ears by spraying them with DCMU. The inhibition of ear photosynthesis increased translocation of labelled assimilates from the flag leaf to the ears, without affecting leaf sugar levels.The application of TIBA to the culm below the ear inhibited auxin movement throught the culm, but had no influence on flag-leaf photosynthesis.These results suggest that, at least in this system, photosynthesis by the flag leaf is regulated directly by the demand for assimilates from the flag leaf and not indirectly through action in the leaf of auxins produced by the sink organs. 相似文献
14.
Photosynthesis and conductance of spring wheat ears: field response to free-air CO2 enrichment and limitations in water and nitrogen supply 总被引:1,自引:0,他引:1
F. Wechsung R. L. Garcia G. W. Wall T. Kartschall B. A. Kimball P. Michaelis P. J. Pinter Jr G. Wechsung S. Grossman-Clarke R. L. Lamorte F. J. Adamsen S. W. Leavitt T. L. Thompson A. D. Matthias & T. J. Brooks 《Plant, cell & environment》2000,23(9):917-929
The mid-day responses of wheat ear CO2 and water vapour exchange to full-season CO2 enrichment were investigated using a Free-Air CO2 Enrichment (FACE) apparatus. Spring wheat [Triticum aestivum (L). cv. Yecora Rojo] was grown in two experiments under ambient and elevated atmospheric CO2 (Ca) concentrations (approximately 370 μ mol mol − 1 and 550 μ mol mol − 1, respectively) combined first with two irrigation (Irr) schemes (Wet: 100% and Dry: 50% replacement of evapotranspiration) and then with two levels of nitrogen (N) fertilization (High: 350, Low: 70 kg ha − 1 N). Blowers were used for Ca enrichment. Ambient Ca plots were exposed to blower induced winds as well the Ca × N but not in the Ca × Irr experiment. The net photosynthesis for the ears was increased by 58% and stomatal conductance (gs) was decreased by 26% due to elevated Ca under ample water and N supply when blowers were applied to both Ca treatments. The use of blowers in the Ca-enriched plots only during the Ca × Irr experiment (blower effect) and Low N supply restricted the enhancement of net photosynthesis of the ear due to higher Ca. In the latter case, the increase of net photosynthesis of the ear amounted to 26%. The decrease in gs caused by higher Ca was not affected by the blower effect and N treatment. The mid-day enhancement of net photosynthesis due to elevated Ca was higher for ears than for flag leaves and this effect was most pronounced under ample water and N supply. The contribution of ears to grain filling is therefore likely to increase in higher Ca environments in the future. In the comparison between Wet and Dry, the higher Ca did not alter the response of net photosynthesis of the ear and gs to Irr. However, Ca enrichment increased the drought tolerance of net photosynthesis of the glume and delayed the increase of the awn portion of net photosynthesis of the ear during drought. Therefore, the role of awns for maintaining high net photosynthesis of the ear under drought may decrease when Ca increases. 相似文献
15.
The stomata and green cells in wheat ears were observed by electron microscopy, and the photosynthetic activity of the ears was measured with an infra-red gas analyser. 1. The awn, glume, palea, lemma, and axis were photosynthetic organs on the wheat ears. Stomata, however, only existed at the green parts in these organs. The ears which had longer awns and higher content of chlorophyll usually showed relatively high photosynthetic rates. 2. The structure and photochemical activity of the chloroplasts in the awns were similar to those in the leaves. 3. The photosynthetic rate of ears could be promoted by increasing light intensity and CO2 concentration. The CO2 compensation point (110 ppm) and the light compensation point (200μE·m-2 · s-1)of ears were higher than those of leaves. 4. The wheat ears had photoresplration. The CO2-releasing rate of the ears under light could be promoted by high O3 concentration. The CO2 outburst and the oscillation in photosynthesis in the awns could be measured. These results suggested that the photosynthetic pathway in the wheat ears was Cspathway. 5. The highest photosynthetic rate of ears emerged at flowering stage. Thereafter, the photosynthetic activity of the ears fell down as the chlorophyll content declined and the grains were filled up. 相似文献
16.
Dry Matter Yields and Photosynthetic Rates of Diploid and Hexaploid Triticum Species 总被引:1,自引:0,他引:1
The above ground dry matter yields of two wild diploid Triticumspecies averaged 76 per cent of that of two hexaploid breadwheat varieties in field trials carried out over five years.A cultivated diploid species, T. monococcum, gave similar drymatter yields to the bread wheat varieties but had a longergrowth cycle. The flag leaves of wild diploid species had higher rates ofphotosynthesis than those of the bread wheat varieties bothwhen expressed per unit area of leaf or per unit weight of chlorophyll.Photosynthetic rates of other organs, expressed per unit weightof chlorophyll were also greater for the wild diploids thanfor hexaploids. For snoots at the stage when their flag leaveswere fully expanded, the investment in photosynthetic machinery,as measured by chlorophyll concentration, was less in the twowild diploids than in the hexaploids. This compensated for thehigh photosynthetic rate of the former, such that the specificgrowth rates, assessed by carbon-14 fixation per unit shootdry matter, were similar. Triticum spp., wheat, dry matter yield, photosynthesis, carbon-14, ploidy 相似文献
17.
Humphreys AM Antonelli A Pirie MD Linder HP 《Evolution; international journal of organic evolution》2011,65(4):1163-1180
Hygroscopically active awns or "bristles" have long intrigued scientists. Experimental evidence shows that they are important for diaspore burial in the correct orientation, thereby increasing successful seed germination and seedling survival. Despite these ecological advantages, 38 of the 280 species of grasses in Danthonioideae lack awns. We provide the first study of awns in a phylogenetic context and show that although the awnless state has arisen ca. 25 times independently, the ecological disadvantage of not having an awn also applies in an evolutionary context. Only in Tribolium and Schismus have awnless ancestors diversified to form a clade of primarily awnless descendents. Several of the awnless species in these genera are annual and we find a significant correlation between the evolution of awns and the evolution of life history. A suite of other diaspore traits accompany the awned or awnless states. We interpret the awn as being the visible constituent of a compound "burial syndrome," the two ecological extremes of which may explain the correlation between awns and life history and provide an explanation why awnless species in Tribolium and Schismus persist. 相似文献
18.
Effect of Nitrogen Fertilizer on Photosynthesis of Several Varieties of Winter Wheat 总被引:2,自引:0,他引:2
The rates of gross photosynthesis of the flag leaf and the nextleaf below (second leaf) in crops of winter wheat were estimatedfrom the 14C uptake of the leaves after exposure to short pulsesof 14CO2. The photosynthetic rates of both leaves during thegrain-filling period decreased with increase in nitrogen fertilizerbecause the intensity of photosynthetically active radiationwas less at the surface of the leaves in the dense crops withadditional nitrogen. In addition, the rate of photosynthesisat saturating light intensity was slightly decreased by nitrogen.The effects of nitrogen, in decreasing the rate of photosynthesisper unit area of leaf and in increasing the leaf-area indexof the top two leaves, were such that the photosynthetic productivityper unit area of land of the flag leaf was increased by nitrogenbut the productivity of the second leaf was unaffected. Applying180 kg N ha1 increased the productivity of the top twoleaves by a factor of 2.3 but increased grain yield by only1.8. The photosynthetic productivity of the second leaf duringthe grain-filling period was about half that of the flag leaf. There was no difference in photosynthetic rate per unit areaof leaves of Cappelle-Desprez and Maris Huntsman which couldaccount for the larger yield of the latter cultivar. There wasa slight indication that the leaves of the semi-dwarf cultivarsMaris Fundin and Hobbit photosynthesized faster than those ofMaris Huntsman. Triticum aestivum L., winter wheat, photosynthesis, nitrogen fertilizer 相似文献
19.
Flag leaves of Triticum urartu, T. monococcum and T. aestivumcv. Professeur Marchal were examined by light and electron microscopyand by separating cells to determine whether differences inleaf anatomy could be related to known differences in theirlight-saturated rates of photosynthesis. Mesophyll cells fromthe three species were lobed and orientated with their longaxis parallel to the veins. The longest, most-lobed cells flankedthe sclerenchyma associated with the veins. Mean cell dimensionswere greatest in Professeur Marchal, but there was no significantdifference in the ratio of the mesophyll cell surface area tocell volume amongst the three species. Flag leaves of T. urartushowed the highest rates of photosynthesis and were also thethickest, with closely-spaced veins from which many of the mesophyllcells radiated. These flag leaves also had significantly more(21.9 per cent) air-filled space, and the highest ratio (15.2)of mesophyll cell surface exposed to this air-filled space perunit leaf area. Ways in which these anatomical characteristicsmay contribute to the higher rate of photosynthesis are discussed. Triticum urartu, Triticum monococcum, Triticum aestivum, flag leaves, morphology, mesophyll 相似文献
20.
Photosynthesis of Ears and Flag Leaves of Wheat and Barley 总被引:3,自引:0,他引:3
Immediately after anthesis ears of spring wheat absorbed lessthan 0.5 mg CO2, per hour in daylight and later evolved CO2,in the light and in the dark. The rate of apparent photosynthesisof the combined flag-leaf lamina and sheath and peduncle (collectivelycalled flag leaf) of two spring wheat varieties, Atle and JufyI, was 34 mg per hour; the rates of the flag leaf andthe ear of two spring barleys, Plumage Archer and Proctor, wereeach about 1 mg per hour. The gas exchange of ears and flag leaves between ear emergenceand maturity accounted for most of the final grain dry weight.The CO2, fixed by the wheat ear was equivalent to between 17and 30 per cent of the grain weight, but more than this waslost by respiration, so assimilation in the flag leaf was equivalentto 11020 per cent of the final grain weight. In barley,photosynthesis in the flag leaf and the net CO2 uptake by theear each provided about half of the carbohydrate in the grain. Barley ears photosynthesized more than wheat ears because oftheir greater surface, and flag leaves of wheat photosynthesizedmore than those of barley because they had more surface anda slightly greater rate of photosynthesis per dm2. 相似文献