不同发育时期追施氮肥对冬小麦旗叶中光合酶活性的影响

小麦开花后,随着旗叶的衰老,旗叶中1,5-二磷酸核酮糖羧化酶（RuBPC）、磷酸烯醇式丙酮酸羧化酶（PEPC）和乙醇酸氧化酶（GO）活性呈下降趋势。随着追施氮肥时期的推迟,光合酶活性呈增加趋势,这意味着氮肥追施时间后移有利于提高小麦光合速率。在旗叶衰老后期,大穗型品种小麦旗叶中光合酶活性略高于多穗型品种小麦。     

Activities of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase and Phosphoenolpyruvate Carboxylase, and Oxygen Evolution in Transgenic Tobacco Plants

Three clones of tobacco transformed with the T-DNA of Agrobacterium rhizogenes Ri plasmid A4b cultivated in vitro on a solid agar medium neither showed pronounced morphological diversity nor significantly differed in chlorophyll (Chl) contents from control plants. However, the transformation caused a 27 to 83 % decay in leaf oxygen evolution and in both ribulose-1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) activities. Therefore, the transformation brought about a reduction of active PEPC as well as activable RuBPC amounts in plant tissues. Individual clones did not mutually differ. In tobacco transformed with A. rhizogenes strain TR101 and grown in soil only the mean leaf area tended to reduce. Chl contents, Chl a/b ratio, oxygen evolution, and activities of both RuBPC and PEPC were insignificantly affected by the transformation.     

Effect of Heat Stress on Photosynthetic Characteristics of Different Green Organs of Winter Wheat During Grain-filling Stage

Four winter wheat ( Triticum aestivum L.) varieties (“JD 8”, “Jing 411”,“Centurk” and “Tam 202”) were used to study the effect of heat stress on photosynthetic characteristics of flag leaf blade, flag leaf sheath, peduncle, glume, lemma and awn during grain-filling stage. The results showed that heat acclimation during grain-filling stage increased thermotolerance of wheat with significant differences among different green organs. During heat stress, the decreases of the efficiency of primary light energy conversion ( Fv/Fm ) of PS and pigment (chlorophyll and carotenoid) content were much slower in peduncle, flag leaf sheath and glume than in flag leaf blade, lemma and awn; and the percentage of decrease in net photosynthetic rate ( Pn ) of ear was lower than that of the flag leaf blade. The measured photosynthetic parameters ( Fv/Fm , Pn and pigment content) of “JD 8”, a relatively heat tolerant variety, declined more slowly than those of the other three varieties during the whole heat stress period.      

Induction of the Inactivation and Degradation of Phosphoenolpyruvate Carboxylase and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase in Maize Leaves by Freezing and Thawing

When frozen leaves of 24-day-old maize (Zea mays L.) plant werethawed on moist filter paper at 26°C (freeze-thaw treatment)several enzymes, including phosphoenolpyruvate carboxylase (PEPC)and ribulose-1,5-bisphosphate carboxylase (RuBPC), were rapidlyinactivated and degraded. The kinetics of the inactivation anddegradation were pseudo first-order, and the halftimes for inactivationof PEPC and RuBPC were 3.2 and 2.4 min, respectively. The effectof the freeze-thaw treatment on the inactivation and degradationdiffered among various enzymes: the residual activities of RuBPC,PEPC, hydroxypyruvate reductase, Cyt c oxidase, NADP-malic enzymeand a-mannosidase 10 min after the start of the thawing treatmentwere 7, 16, 54, 64, 97 and 98% of the initial respective levels.Thirty min after the starting of thawing treatment, the amountsof total soluble protein, the large subunit of RuBPC, the smallsubunit of RuBPC, the PEPC subunit and the NADP-malic enzymesubunit had fallen to 61, 2, 16, 8, and 66% of the initial respectiveamounts. The effect of freeze-thaw treatment on PEPC was greater in oldleaves than in young leaves. There was a steady increase ofthe rate of degradation of PEPC by freeze-thaw treatment asplants aged from 6 to 24 days. These results are discussed inthe context of protein degradation in plant cells. (Received August 9, 1993; Accepted January 10, 1994)     

Variation in amounts of pyruvate, orthophosphate dikinase, and some other enzymes of the c(4) pathway in some wheat species

First leaves and flag leaves of the wheat species Triticum aestivum cv Anza (6×), T. boeoticum Boiss (2×) L. were examined for content of pyruvate, orthophosphate dikinase (PPDK), phosphoenolpyruvate carboxylase (PEPC), and ribulose 1,5-bisphosphate carboxylase (RuBPC) by protein blot analyses using antibodies to maize leaf enzymes and by activity assays. In agreement with previous reports, the amount of RuBPC per mesophyll cell was about 3 times more in the hexaploid species, T. aestivum, than in the diploid species, T. boeoticum, both in first leaves and in flag leaves. In contrast, the level of PPDK polypeptide was nearly 3-fold higher per unit leaf area in the first leaf and 63% higher in the flag leaf of this diploid species compared to this hexaploid species. There was no significant difference in the levels of polypeptide and enzyme activity of PEPC between diploid and hexaploid wheat. Despite this significantly greater level of PPDK in the diploid species, the actual amount of PPDK could still supply only a limited amount of the enzyme activity necessary to provide phosphoenolpyruvate (PEP) for any putative intracellular C₄ carbon shuttle providing carbon to RuBPC. Thus, this difference in enzyme amount could not by itself account for the reported high rates of net photosynthesis at high light intensity in T. boeoticum. Together with reported anatomical differences between the diploid and hexaploid species, however, this biochemical difference may be of physiological importance.     

Activities of Ribulose Bisphosphate Carboxylase and Phosphoenolpyruvate Carboxylase and C-Bicarbonate Fixation during in Vitro Culture of Pinus radiata Cotyledons

The activities of ribulose bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC), as indicators of autotrophic and nonautotrophic CO₂ fixation, were measured in excised cotyledons of Pinus radiata D. Don cultured for 21 days under shoot-forming (SF) and nonshoot-forming (NSF) conditions. The activity of RuBPC was found to increase in both SF and NSF cultures during the initial 5 days of culture. However, it leveled off from day 5 to day 10 and subsequently began to decrease until the end of the culture period under the SF conditions. In contrast, in the NSF cultures, RuBPC activity increased until day 15, when it was twofold higher than the maximum activity found in the SF cultures. An increase in PEPC activity of about 2.5 times the level of activity in freshly excised cotyledons was observed during the initial 5 days of culture under the SF conditions. PEPC activity began to decline after day 5 until it reached the level of activity seen in NSF cotyledons by day 15. In contrast, the activity of PEPC did not show any significant increase during the initial 10 days of culture under the NSF conditions. The K_m (phosphoenolpyruvate) of PEPC from SF cotyledons was about 35% higher than that of NSF cotyledons. Cotyledons from two culture periods (days 5 and 15) were incubated for 15 seconds with NaH¹⁴CO₃. The label in the malate and asparatate fractions as a percentage of total ¹⁴C incorporation was 3 times higher in the SF cotyledons than in the NSF cotyledons. A higher incorporation of ¹⁴C into products of photosynthesis under the NSF conditions was also observed.     

Activities of Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase,and Dry Mass Accumulation in Brassica juncea following Defoliation

The effect of 30 % defoliation of shaded leaves in lower layers of plant was studied on activities of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase (RuBPC), leaf dry mass per unit leaf area, and plant dry mass of mustard (Brassica juncea). Removal of 30 % of leaves resulted in increased CA and RuBPC activities of leaves, and leaf and plant dry masses.     

不同供水条件下冬小麦叶与非叶绿色 器官光合日变化特征

为揭示小麦叶片与非叶绿色器官的光合活性在一日中的变化特性及其在器官间的差异性,探讨群体及不同器官光合日变化对不同供水条件的响应特征,在田间设置生育期不灌水(I0)、灌2水(I2,拔节水＋开花水)和灌4水(I4,起身水+孕穗水+开花水+灌浆水)3个处理,于灌浆期测定了群体光合与呼吸速率的日变化, 旗叶片、叶鞘、穗、穗下节间各器官光合速率、蒸腾速率、气孔导度及叶绿素荧光参数的日变化。结果表明,灌浆期小麦穗和穗下节间光合速率日变化呈单峰曲线,而旗叶叶片与旗叶鞘光合速率均呈双峰型,表现出不同程度的午休。随着灌水次数减少,各器官光合速率降低,叶片对严重水分亏缺的反应大于各非叶器官。器官光合速率的日变化与F_v/F_m变化相一致,而与气孔导度日变化有较大差异。各器官上午的累积光合量均高于下午,上午光合量占日总光合量的比例为51％-62％,随着灌水次数减少而增大。不同灌水处理群体光合速率、呼吸速率日变化均未出现午休现象。春季浇2水处理与春浇4水处理相比,灌浆期群体光合速率及日光合积累量没有显著差异。综合研究认为,小麦叶与非叶器官光合性能及其日变化特征有较大不同,非叶光合对水分亏缺的敏感性低于叶片,生育期浇2水可以获得与浇4水相似的群体日光合积累量。     

Activities of Phosphoenolpyruvate Carboxylase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase in Leaves and Fruit Pericarp Tissue of Different Coffee (Coffea sp.) Genotypes

In order to study photosynthetic characteristics, phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activities as well as soluble protein and chlorophyll contents were determined in leaf and fruit pericarp samples from diverse coffee genotypes (Coffea arabica cv. Colombia, Caturra, Caturra Erecta, San Pacho, Tipica, C. stenophylla, C. eugenioides, C. congensis, C. canephora, C. canephora cv. Arabusta, C. arabica cv. Caturra×C. canephora and Hibrido de Timor. We found a slightly higher PEPC activity in fruit pericarp than in leaves, while RuBPCO activity was much lower in pericarp than leaf tissue. Partial purification of PEPC and RuBPCO was carried out from leaves of C. arabica cv. Caturra and Michaelis-Menten kinetics for RuBPCO (K_m CO₂ = 5.34 µM), (K_m RuBP = 9.09 µM) and PEPC (K_m PEP = 19.5 µM) were determined. Leaf tissues of Colombia, Hibrido de Timor, and Caturra consistently showed higher content of protein [55.4–64.4 g kg^–1 (f.m.)] than San Pacho, C. stenophylla, Tipica, Caturra Erecta, and Caturra×C. canephora [25.6–36.9 g kg^–1 (f.m.)] and C. canephora cv. Arabusta, Borbon, C. congensis, C. eugenioides, and C. canephora [16.1–21.1 g kg^–1 (f.m.)].     

The effect of ammonium and nitrate on CO2 assimilation,RuBP and PEP carboxylase activity and dry matter production in wheat

Photosynthetic¹⁴CO₂ assimilation, ribulose 1, 5-bisphosphate carboxylase (RuBPC), phosphoenol pyruvate carboxylase (PEPC) and dry matter (DM) production were examined in wheat under varying levels and forms of nitrogen.¹⁴CO₂ assimilation increased gradually after germination reaching a peak value at anthesis, followed by a sharp decline. A similar pattern was observed for both the carboxylases, RuBPC and PEPC activities. Increase in nitrogen levels, in general, brought about a significant increase over the control (zero-nitrogen) in¹⁴CO₂ assimilation, RuBPC, PEPC activities and DM production. There were no significant differences in RuBPC activity and¹⁴CO₂ assimilation with respect to the forms of nitrogen. Significantly higher PEPC activity and DM was observed in plants supplied with nitrate-nitrogen (NO₃-N), as compared to those supplied with ammonium-nitrogen (NH₄-N). The significance of PEPC activity in C₃ photosynthesis is discussed in relation to DM distribution.     

Developmental regulation of photosynthate distribution in leaves of rice

mRNA expression patterns of genes for metabolic key enzymes sucrose phosphate synthase (SPS), phosphoenolpyruvate carboxylase (PEPC), pyruvate kinase, ribulose 1,5-bisphosphate carboxylase/oxygenase, glutamine synthetase 1, and glutamine synthetase 2 were investigated in leaves of rice plants grown at two nitrogen (N) supplies (N_0.5, N_3.0). The relative gene expression patterns were similar in all leaves except for 9^th leaf, in which mRNA levels were generally depressed. Though increased N supply prolonged the expression period of each mRNA, it did not affect the relative expression intensity of any mRNA in a given leaf. SPS V_max, SPS limiting and PEPC activities, and carbon flow were examined. The ratio between PEPC activity and SPS V_max was higher in leaves developed at the vegetative growth stage (vegetative leaves: 5^th and 7^th leaves) than in leaves developed after the ear primordia formation stage (reproductive leaves: 9^th and flag leaves). PEPC activity and SPS V_max decreased with declining leaf N content. After using ¹⁴CO₂ the ¹⁴C photosynthate distribution in the amino acid fraction was higher in vegetative than in reproductive leaves when compared for the same leaf N status. Thus, at high PEPC/SPS activities ratio, more ¹⁴C photosynthate was distributed to the amino acid pool, whereas at higher SPS activity more ¹⁴C was channelled into the saccharide fraction. Thus, leaf ontogeny was an important factor controlling photosynthate distribution to the N- or C-pool, respectively, regardless of the leaf N status.     

Photosynthetic Characteristics of Non-Leaf Organs of Winter Wheat Cultivars Differing in Ear Type and their Relationship with Grain Mass Per Ear

Chlorophyll content, photosystem 2 functioning (F_v/F_m, F_v/F₀), activity of ribulose-1,5-bisphosphate carboxylase/oxygenase, and net photosynthetic rates (P _N) of flag leaf blade, sheath, peduncle, and ear organs were assessed in large-ear type (Pin 7) and small-ear type (ND93) wheat cultivars. Some differences were found in photosynthetic properties between different green plant parts, the values of all studied parameters in ear parts being higher in Pin7 than in ND93. Furthermore, ear surface areas and ear P _N in 26 wheat genotypes measured at anthesis showed highly significant positive correlation with grain mass per ear. Hence a greater capability of ear photosynthesis may result in a greater grain yield in large-ear type cultivars.     

The photosynthetic characteristics of differently shaped leaves in Populus euphratica Olivier

There is a distinct leaf shape polymorphism within a single plant of P. euphratica Olivier. The anatomical structure, carbon isotope discrimination (Δ¹³C), and stomatal and photosynthetic behaviour were investigated in broad-ovate (BOL) and lanceolate (LL) leaves, located at the top and bottom in crown, respectively, of a mature Euphrates poplar growing in its native habitat. Both types of leaves had a non-Kranz anatomy and low Δ¹³C values. However, Δ¹³C of a LL was in average 3.2‰ larger than that of a BOL. In comparison with the LL, the BOL had a smaller stomatal conductance, causing subsequent decreases in transpiration rate and ratio of CO₂ concentrations in intercellular spaces to air. Carbon assimilation rate and water use efficiency were higher in the BOLs than in the LLs. The BOL exhibited C₄-like enzymological features, the activity of glycollate oxidase, and the ratio of activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) to phosphoenolpyruvate carboxylase (PEPC) was lower in BOL than in LL throughout the whole growing season. The lowered ratio of RuBPC/PEPC in BOL was mainly associated with a marked decline in the activity of RuBPC, and only a slight increase in the activity of PEPC. These differences might contribute to microclimate adaptation in both types of leaves. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cold Inactivation of Phosphoenolpyruvate Carboxylase and Pyruvate Orthophosphate Dikinase from the C4 Perennial Plant Atriplex halimus

Phosphoenolpyruvate carboxylase (PEPC) and pyruvate orthophosphate dikinase (PPDK) cold inactivation was studied in leaf extracts from Atriplex halimus L. Both enzyme activities gradually reduced as the temperature and the total soluble protein decreased. Mg²⁺ at a concentration of 10 mM stabilized PEPC and PPDK activities against cold inactivation. At low Mg²⁺ concentration (4 mM), PEPC was strongly protected by phosphoenolpyruvate, glucose-6-phosphate, and, partially, byL-malate, while PPDK was protected by PEP, but not by its substrate, pyruvate. High concentrations of compatible solutes (glycerol, betaine, proline, sorbitol and trehalose) proved to be good protectants for both enzyme activities against cold inactivation. When illuminated leaves were exposed to low temperature, PPDK was partially inactivated, while the activity of PEPC was not altered.     

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

The grapevine (Vitis vinifera L. cv. Riesling) plants subjected to water deficit were studied for changes in relative water content (RWC), leaf dry mass, contents of chlorophyll (Chl), total leaf proteins, free amino acids, and proline, and activities of ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR), and protease. In water-stressed plants RWC, leaf dry matter, Chl content, net photosynthetic rate (P _N), and RuBPC and NR activities were significantly decreased. The total leaf protein content also declined with increase in the accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. A significant two-fold increase in proline content was recorded.     

The photosynthetic characteristics of differently shaped leaves in Populus euphratica Olivier

There is a distinct leaf shape polymorphism within a single plant of P. euphratica Olivier. The anatomical structure, carbon isotope discrimination (Δ¹³C), and stomatal and photosynthetic behaviour were investigated in broad-ovate (BOL) and lanceolate (LL) leaves, located at the top and bottom in crown, respectively, of a mature Euphrates poplar growing in its native habitat. Both types of leaves had a non-Kranz anatomy and low Δ¹³C values. However, Δ¹³C of a LL was in average 3.2‰ larger than that of a BOL. In comparison with the LL, the BOL had a smaller stomatal conductance, causing subsequent decreases in transpiration rate and ratio of CO₂ concentrations in intercellular spaces to air. Carbon assimilation rate and water use efficiency were higher in the BOLs than in the LLs. The BOL exhibited C₄-like enzymological features, the activity of glycollate oxidase, and the ratio of activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) to phosphoenolpyruvate carboxylase (PEPC) was lower in BOL than in LL throughout the whole growing season. The lowered ratio of RuBPC/PEPC in BOL was mainly associated with a marked decline in the activity of RuBPC, and only a slight increase in the activity of PEPC. These differences might contribute to microclimate adaptation in both types of leaves.     

Mulberry Leaf Metabolism under High Temperature Stress

Effects of high temperature on the activity of photosynthetic enzymes and leaf proteins were studied in mulberry (Morus alba L. cv. BC2-59). A series of experiments were conducted at regular intervals (120, 240 and 360 min) to characterize changes in activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and sucrose phosphate synthase (SPS), photosystem 2 (PS 2) activity, chlorophyll (Chl), carotenoid (Car), starch, sucrose (Suc), amino acid, free proline, protein and nucleic acid contents in leaves under high temperature (40 °C) treatments. High temperature markedly reduced the activities of RuBPC and SPS in leaf extracts. Chl content and PS 2 activity in isolated chloroplasts were also affected by high temperature, particularly over 360 min treatment. Increased leaf temperature affected sugar metabolism through reductions in leaf starch content and sucrose-starch balance. While total soluble protein content decreased under heat, total amino acid content increased. Proline accumulation (1.5-fold) was noticed in high temperature-stressed leaves. A reduction in the contents of foliar nitrogen and nucleic acids (DNA and RNA) was also noticed. SDS-PAGE protein profile showed few additional proteins (68 and 85 kDa) in mulberry plants under heat stress compared to control plants. Our results clearly suggest that mulberry plants are very sensitive to high temperature with particular reference to the photosynthetic carbon metabolism.     

An Oligonucleotide Primer System for Amplification of the Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Genes of Bacteria of Various Taxonomic Groups

Based on the analysis of GenBank nucleotide sequences of the cbbL and cbbM genes, coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), the key enzyme of the Calvin cycle, a primer system was designed that allows fragments of these genes about 800 bp long to be PCR-amplified for various photo- and chemotrophic bacteria. The efficiency of the designed primer system in detection of RuBPC genes was demonstrated in PCR with DNA of taxonomically diverse bacteria possessing RuBPC genes with a known primary structure. Nucleotide sequences of RuBPC gene fragments of bacteria belonging to the genera Acidithiobacillus, Ectothiorhodospira, Magnetospirillum, Methylocapsa, Thioalkalispira, Rhodobacter, and Rhodospirillum were determined to be deposited with GenBank and to be translated into amino acid sequences and subjected to phylogenetic analysis.     

Phosphoenolpyruvate Carboxylase and CarbonEconomy of Apple Seedlings

Seeds of apple cv. Golden Delicious were germinated and cultivatedin the greenhouse until the third leaf emerged. Respirationofgerminating seeds or photosynthesis of the first leaves wasmeasured by infra-red gas analysis and porometry, respectively.To study the role of phosphoenolpyruvate carboxylase (PEPC),the dominant carboxylase in the carbon economy, its CO₂ refixationpotentialwas related to the amount of CO₂ lost in respiration. With arange of 0.2 (dry seeds) to 18 (cotyledons) µmol CO₂ h^–1g^–1 PEPC activity resembled or exceeded the amount ofC0₂ lost in respiration before the third leaf developed. Itis concludedthat PEPC largely contributes to economize the carbonmetabolism of apple seedlings before they become photosyntheticallycompetent. Key words: Apple (Malus pumila Mill.) seedling, carbon economy, phosphoenolpyruvate carboxylase, photosynthesis, respiration