Enzyme Activities Associated with Carbon Dioxide Exchange in Illuminated Leaves of Hordeum vulgare L.: III. Effects of Concentration and Form of Nitrogen Supplied on Carbon Dioxide Compensation Point

Increasing the nitrate concentration in the nutrient media wasfound not to influence the carbon dioxide compensation point(). However, a higher value of was obtained in the presenceof ammonia nitrogen in the nutrient media. Increasing the nitrateconcentration in the media gave a higher activity of RuDP carboxylase,nitrate reductase, glycollate oxidase, and catalase. Similarlythe plants grown in ammonia nitrogen showed higher activitiesof RuDP carboxylase and catalase, and a considerably higherglycollate oxidase activity.     

Enzyme Activities Associated with Carbon Dioxide Exchange in Illuminated Leaves of Hordeum vulgare L.: I. Effects of Light Period, Leaf Age, and Position, on Carbon Dioxide Compensation Point ({Gamma})

The carbon dioxide compensation point () was found to vary underconstant environmental conditions, as the duration of lighttreatment increased, and also with leaf age. The activitiesof RuDP carboxylase, catalase, glycollate oxidase, and nitratereductase were found to vary with duration of the light treatmentduring the course of a single day. RuDP carboxylase activity was found to exhibit a rhythmic fluctuationof activity with age, which had a frequency common to all theleaves examined. The activities of RuDP carboxylase, glycollateoxidase, and nitrate reductase in the leaves was found to increasewith ascending leaf position; the activities generally decreasedwith leaf age. The ratio of nitrate reductase activity to RuDPcarboxylase activity was found to give an excellent correlationwith measured T, and the value of nitrate reductase as an indirectmeasure of photorespiration and the relationship between nitrogenmetabolism and photorespiration is discussed.     

Enzyme Activities Associated with Carbon Dioxide Exchange in Illuminated Leaves of Hordeum vulgare L.: II. Effects of External Concentrations of Carbon Dioxide and Oxygen

Plants grown in a high carbon dioxide environment (< 1 percent) were found to have increased levels of RuDP carboxylase,and suppressed activities of catalase, glycollate oxidase, andnitrate reductase, enzymes all associated with the peroxisome.Similarly, plants grown in low oxygen concentrations showedsuppressed activities of the peroxisomal enzymes. However, underthese conditions RuDP carboxylase activity was also suppressed.These results further suggest that nitrate reductase activityis associated with photorespiration.     

Precise Measurements of Carbon Dioxide Exchange by Illuminated Leaves near the Compensation Point

The results of precise measurements of rates of carbon dioxideassimilation at low external concentrations of carbon dioxideand of rates of carbon dioxide output into virtually carbondioxide-freeair show that linear extrapolations of the carbon dioxide intakecurve plotted against the external concentrations of carbondioxide give an exaggerated estimate of the rate of carbon dioxideoutput from illuminated leaves into carbon dioxide-free air. The shape of the exchange curve suggests that the rate of endogenousproduction of carbon dioxide changes at external concentrationsin the region of the carbon dioxide compensation point ().     

Differential Effects of Carbon Dioxide on the Growth Rates of Coleoptiles and the Enclosed Leaves of Hordeum vulgare L. seedlings

Carbon dioxide appears to modulate the growth rates of the barley(Hordeum vulgare L.) coleoptile and the enclosed leaves duringearly germination. Its effect is to stimulate the coleoptileto elongate at a rate equal to or greater than that of the enclosedleaves. Such stimulation was observed directly in barley coleoptilesfloated on CO₂-sarurated water or indirectly using a DCMU solution.This mechanism ensures that the tender leaves remain enclosedwithin the structurally strong coleoptile sheath until the shootpushes through the soil surface. It is suggested that CO₂ respiredby the enclosed leaves effects this modulation: the CO₂ couldpass into the coleoptile chamber and thence into the coleoptilevia stomata present on coleoptile inner walls.     

Effect of Light Intensity on Efficiency of Carbon Dioxide and Nitrogen Reduction in Pisum sativum L

Photosynthetic efficiency, primary productivity, and N₂ reduction were determined in peas (Pisum sativum L. var. Alaska) grown at light intensities ranging from severely limiting to saturating. Plants grown under higher light intensities showed greater carboxylation and light capture potential and higher rates of net C exchange. Uptake of N₂, computed from measured C₂H₂ reduction and H₂ evolution rates, also increased with growth light intensity, while the previously proposed relative efficiency of N₂ fixation, based on these same parameters, declined. The plot of N/C ratios (total nitrogen content/plant dry weight) increased hyperbolically with light intensity, and the plot of N₂/CO₂ uptake ratios (N₂ uptake rate/net CO₂ uptake rate) increased linearly. Both plots extrapolated to the light compensation point. The data indicate that the relative efficiency of N₂ fixation is not necessarily correlated with maximum plant productivity and that evaluation of a plant's capacity to reduce N₂ is related directly to concurrent CO₂ reduction. A measure of whole plant N₂ fixation efficiency based on the N₂/CO₂ uptake ratio is proposed.     

The Effect of Water Stress upon Polyamine Levels in Barley (Hordeum vulgare L.) Leaves

The effect of water stress on leaf polyamine content of fourHordeum vulgare varieties, Alger/Ceres, Palmella Blue, Rihaneand Roho, with different drought characters was studied After6 d without water Alger/Ceres, Palmella Blue and Rihane hadaccumulated putrescine, although only in concentrations up totwice those found in the controls, but Roho had a decreasedputrescine content. However, one common response was identified;the accumulation and subsequent loss of putrescine was dependentupon the maintenance and loss of leaf turgor respectively. Consequentlyvarietal differences in putrescine accumulation were relatedto water consumption rates and the extent of osmotic adjustment.Spermine behaved in a similar manner to putrescine but spermidinelevels always decreased. Polyamine levels were never high enoughto be an important component of solute accumulation. Prolinelevels were 150-fold higher and glycine-betaine levels 50-foldhigher than polyamines in stressed plants. Proline and glycine-betaineaccumulation occurred once a threshold turgor was reached, whichin Roho appeared to be a reduction by 0•2–0•25MPa or 30–40%. The importance of polyamine accumulationduring water stress is discussed. Key words: Hordeum vulgare, polyamine, water stress     

Effect of Light Intensity, Carbon Dioxide Concentration, and Leaf Temperature on Gas Exchange of Spray Carnation Plants

The rates of CO₂ assimilation by potted spray carnation plants(cv. Cerise Royalette) were determined over a wide range oflight intensities (45–450 W m^–2 PAR), CO₂ concentrations(200–3100 vpm), and leaf temperatures (5–35 °C).Assimilation rates varied with these factors in a way similarto the response of single leaves of other temperate crops, althoughthe absolute values were lower. The optimal temperature forCO₂ assimilation was between 5 and 10 °C at 45 W m^–2PAR but it increased progressively with increasing light intensityand CO₂ concentration up to 27 °C at 450 W m^–2 PARand 3100 vpm CO₂ as expressed by the equation TOpt = –6.47-h 2.336 In G + 0.031951 where C is CO₂ concentration in vpmand I is photo-synthetically active radiation in W m^–2.CO₂ enrichment also increased stomatal resistance, especiallyat high light intensities. The influence of these results on optimalization of temperaturesand CO₂ concentrations for carnation crops subjected to dailylight variation, and the discrepancy between optimal temperaturesfor growth and net photosynthesis, are discussed briefly     

The Effect of Light Intensity on the Release of Ethylene from Leaves

When leaf discs of Xanthium strumarium L. a C₃ plant, or Zeamays L. a C₄ plant, are incubated in 1-aminocyclopropane-l-carboxylicacid (ACC) in closed flasks, ethylene is released. The rateof ethylene release appears to be dependent on the levels oflight and CO₂ available for photosynthesis in the tissues. In Xanthium the rate of ethylene release is lower in the lightthan in the dark regardless of the presence or absence of addedbicarbonate as a source of CO₂. The inhibition of ethylene releaseis most apparent in the absence of added bicarbonate (i.e. atthe CO₂ compensation point), and at light intensities sufficientto saturate photosynthesis (had the CO₂ level in the test flaskbeen maintained). In contrast, light dramatically promotes therate of ethylene release from Zea leaf tissue when the CO₂ levelis maintained above the CO2 compensation point. The rate ofethylene release from either Xanthium or Zea, incubated withor without added bicarbonate, does not appear to be alteredby further increasing the light intensity above the minimallevels sufficient to saturate photosynthesis. In the closed system used in these studies and at a light intensitysufficient to saturate photosynthesis, Xanthium and Zea leaftissue both appear to release comparable amounts of ethylenefrom ACC when the data is expressed on a chlorophyll basis.However, in Xanthium the rate of ethylene release is similarin light and dark, while in Zea the rate in the light is muchgreater than in the dark when the data is expressed either ona leaf area or on a chlorophyll basis. It is suggested thatthe different responses of these tissues to light/dark transientsmay reflect differences in their ability to metabolize ACC and/ordifferences in their ability to retain and metabolize ethyleneitself.     

红光和Ca~(2 )对与绿豆下胚轴伸长有关的细胞壁酶的影响

作为去黄化过程中的一个反应——植物茎伸长受光抑制的现象,已有不少研究。人们发现,胚轴长度受光的调节,对红光尤其敏感（lion1982）。红光抑制绿豆下胚轴切段伸长（王小菩和潘瑞炽1990）,却促进绿豆下胚轴原生质体膨大,钙在此过程中起第二信使的作用（龙程等1994a,b）,但红光促进原生质体膨大却抑制切段伸长的机理尚不清楚。我们认为问题的症结可能在细胞壁,因为植物细胞的生长（伸长和扩大）在很大程度上取决于细胞壁的松弛和伸展。植物细胞只有当细胞壁酶作用于细胞壁使之松弛时,才能在膨压的作用下吸水长大（Taiz1984）。因…     

Regulation of Fructan Metabolism in Leaves of Barley (Hordeum vulgare L. cv Gerbel)

Excised primary leaf blades of barley (Hordeum vulgare L. cv Gerbel) rapidly synthesized large quantities of fructan in the light and, upon transfer to the dark, they rapidly degraded it again. In the course of such a light/dark cycle the activities of sucrose-sucrose-fructosyltransferase (SST), fructan hydrolase, and invertase were measured in cell-free extracts of the blades. SST activity increased 20-fold within 24 hours in the light and disappeared again upon transfer to the dark during a similar period of time. Cycloheximide inhibited the increase of SST activity in the light indicating de novo synthesis. The loss of SST activity in the dark, however, was unaffected by cycloheximide. No SST activity appeared in the light if photosynthesis was inhibited by lowering the CO₂ concentration in the atmosphere. However, SST activity and fructan synthesis were induced even in the dark and at a low CO₂ concentration when the leaf blades were immersed in a solution of sucrose. Several other sugars, maltose and fructose in particular, had the same effect. Trehalose induced SST activity but no fructan synthesis occurred. The activities of fructan hydrolase and invertase changed little during the light/dark cycle. It is suggested that the control of SST activity in conjunction with the supply of photosynthates plays a key role in the regulation of fructan metabolism.     

The genotoxic effects of Logran on Hordeum vulgare L. and Triticum aestivum L

In the present study, the cytogenetic effects of the herbicide Logran on root tip cells of Triticurn aestivum L. and Hordeum vulgare L. and changes of total protein content in root tip meristems were studied. The seeds of plants were treated with various concentrations of Logran (125, 250, 500 microg/ml) for 3 and 6 h. The percentages of abnormal cells were seen to increase with increasing treatment period and concentrations. The most dominant types of observed abnormalities were C-mitosis, distributed metaphase and anaphase, stickiness. All the used concentrations of Logran significantly induced a number of chromosomal aberrations in root tip cells of Hordemrn vulgare L. and Triticum aestivum L. Logran also decreased mitotic index. The decrease of protein content in root tips of Triticum aestivum L. is significant at all the treated concentrations and treatment periods when compared with control.     

低温胁迫下不同光照条件对锦熟黄杨抗氧化酶活性的影响

研究了锦熟黄杨（Buxus sempervirens L.）在低温胁迫下不同光照条件（12 h光照/12 h黑暗、24 h全光、24 h全黑）对其抗氧化酶活性的影响,结果表明：低温不同光照条件下细胞膜透性和丙二醛含量均高于对照（20℃ 12 h光照/12 h黑暗）,细胞膜透性和丙二醛含量在5℃ 24 h光照条件下最大;低温胁迫下SOD活性高于对照,并在5℃ 24 h光照条件下达到最高值;CAT的活性仍维持较高水平,5℃ 12 h光照/12 h黑暗显著高于对照及其它处理;在低温有光照条件下,POD活性升高,黑暗条件下POD活性低于对照。低温胁迫下POD、SOD和CAT的活性均呈上升趋势,可能是植株具有较强抗性的原因。     

Effect of Several Transpiration Suppressants on Carbon Dioxide and Water Vapor Exchange of Citrus and Grapevine Leaves

Several transpiration suppressants, (phenyl mercuric acetate, Tag 16 (polyethylen emulsion) R₁₄-poly (ethylene adipate) 4–4 Diphenylmethan diisocyanate), which are known to either close stomata or form thin films on leaves, were sprayed on citrus and grapevine seedlings. Water vapor and carbon dioxide exchange of single leaves were measured by means of infra red gas analyzer and L1C1 hygrosensors. The effects of the chemicals were evaluated by analyzing net photosynthesis, transpiration, mesophyll resistance to CO₂ compensation concentration and respiration. All the chemicals tested increased either mesophyll resistance or CO₂ compensation point to various degrees. It is concluded that none of the chemicals tested acted solely on epidermal resistance. All chemicals reduced photosynthesis, but the ratio of photosynthesis to transpiration increased in most cases in grapevine but not in citrus. Different chemicals acted differently on citrus and grapevine. The method of analysis used enabled us to evaluate separately the relative effect of a chemical on mesophyll resistance and respiration.     

The role of hydrogen bonding in the cuticular wax of Hordeum vulgare L.

The role of hydrogen bonding in the cuticular wax of Hordeum vulgare L. has been investigated by comparing differential scanning calorimetry and X-ray powder diffraction results of the wax with those of n-alkane mixtures with chain-length distributions resembling that of the wax. It is concluded that hydrogen bonding prevents separation of the short and long chain-length distributions and results in the formation of an amorphous component which is large compared with that of a typical paraffinic wax. It seems that the longer ester chains (39 ≥n≥ 50) bridge the amorphous zone containing chain-ends between two adjacent layers of shorter chains (20 ≥n≥ 33), where n is the number of carbon atoms per chain. In contrast to a paraffinic wax, which has a monolayered structure, this plant wax has a bilayered structure.     

The Effects of Light Intensity and Carbon Dioxide Concentration on the Growth of Chrysanthemum morifolium cv. Bright Golden Anne

Rooted cuttings were grown in controlled-environment cabinetsat daily visible light totals of 31, 63, 125, and 250 J cm^–28-h day^–1 and carbon dioxide concentrations of 325 and600 ppm. The experiment was repeated on another occasion withthe inclusion of a further carbon dioxide level of 900 ppm.A 5-h tungsten night break was used in the first week to delayflower initiation The plants in the various treatment combinationswere sampled by frequent small harvests for leaf area and freshand dry weights of leaf, stem, root, and flower, and also forvarious morphological features. Other growth measures were obtainedby manipulation of the primary data, including the fitting ofprogress curves. Plants were respaced at intervals to minimizemutual shading. There was an increase in total dry-matter production with increasinglight and carbon dioxide, with a small positive interactionbetween them. Plants in one experiment had a somewhat higherunit leaf rate and a lower leaf-area ratio, the latter beingdue to a slightly smaller leaf-weight ratio. The effects ofadditional carbon dioxide were largely accounted for by increasedphotosynthesis. Although there were substantial differencesin specific leaf area between treatment combinations withineach experiment, the leaf-weight ratio was little altered inthe period of vegetative growth. The inverse relationship betweenspecific leaf area and unit leaf rate showed a very similartrend for all combinations of light and carbon dioxide concentration.Leaf area was a linear function of absolute leaf water contentfor all treatment combinations within an experiment, but therewas a small significant difference between occasions. Flower development was extremely delayed in the lowest lightlevel and substantially delayed at the next higher level. Thenumber of leaves below the flower decreased with increasinglight level Flower weight increased with increasing light above63 J cm^–2 8-h day^–1 and with increasing carbon dioxideconcentration, there being a positive interaction between them The initial weight and leaf area of cuttings differed for thetwo experiments, and although the results on the two occasionswere in the same direction, their magnitudes were different.Some of the discrepancy was eliminated by expressing the variousgrowth measures as functions of plant dry weight, but therewas evidently a difference in the potential for growth of thetwo batches of cuttings. The plants which were initially smallerhad a higher average unit leaf rate which, due to a higher leafwater content, was not offset by a lower leaf area ratio.     

Enzymology of Fructan Synthesis in Grasses: Properties of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves (Hordeum vulgare L. cv Gerbel)

Fructan synthesis was induced in excised primary leaf blades of Hordeum vulgare L. cv Gerbel by illumination in 30 millimolar fructose. This treatment induced a 26-fold increase of sucrose-sucrose-fructosyltransferase (SST, EC 2.4.1.99) activity within 24 hours. Acid invertase (EC 3.2.1.26) activity remained about constant. By preparing protoplasts from induced leaves, approximately 80% of the invertase activity was removed with the cell walls while SST was retained. The protoplast homogenate was used to partially purify and characterize SST. Acid precipitation (pH 4.75) and anion exchange chromatography (fast protein liquid chromatography on Mono `Q') resulted in a recovery of about 80% of total SST activity. The principal activity (SST 1), accounting for 85% of the activity recovered, was purified about 200-fold. It was essentially free of invertase activity and catalyzed the synthesis of a trisaccharide which co-chromatographed with isokestose (1F-β-fructosylsucrose). The remaining 15% of SST activity (SST 2) was purified about 35-fold. It retained substantial invertase activity and catalyzed the synthesis of only one trisaccharide which co-chromatographed with kestose (6F-β-fructosylsucrose). It is concluded that barley leaves which store mainly fructan of the phlein type (β-2-6 polyfructosylsucrose), nevertheless contain sucrose-sucrose 1F-β-d-fructosyltransferase as the key enzyme of fructan synthesis.     

Effect of anther orientation on microspore-callus production in barley (Hordeum vulgare L.)

Barley anthers from cold pretreated spikes produced no or few calluses when plated with both loculi in contact with the medium (flat). When anthers were plated with only one loculus in contact with the medium (up), a high proportion of the anthers produced calluses. The top loculus of the up anthers was most productive. Flat anthers, when compared with up anthers, were not only slower to produce multicellular pollen grains (MCPs) and microcalluses, but also produced fewer of them and ceased production earlier. The MCPs and microcalluses in flat anthers grew more slowly and few developed beyond the 30 cell stage. These results establish the importance of anther orientation for barley anther culture.     

The inheritance of genetic markers in microspore-derived plants of barley Hordeum vulgare L.

Summary Biochemical, molecular and morphological markers have been used to monitor the segregation of alleles at major gene loci in microspore-derived lines of four spring barley crosses and their parents. Significant deviations from the expected Mendelian ratios were observed for four of the ten markers studied in the cross. Distorted ratios were associated with loci located on chromosomes 4H and 6H. The differential transmission of alleles was in favour of the responsive parent (Blenheim) used in the anther culture studies. For the -Amy-1 locus on chromosome 6H, the preferential transmission of Blenheim alleles was most pronounced in the haploid regenerants that were colchicine treated. These results are discussed in relation to the genetic control of androgenetic response in barley and with respect to the exploitation of another culture in barley improvement.