Metabolism of Ammonium Ion and Glutamate in Relation to Nitrogen Supply and Utilization during Grain Development in Barley

Changes in the activity of a number of enzymes concerned with amino acid synthesis and metabolism were recorded for the endosperm, testa pericarp, and embryo of developing barley (Hordeum distichum L.) grains. Both glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase activities were present in all tissues and at all ages examined. Glutamate dehydrogenase activity was largely confined to endosperm while glutamine synthetase activity was mainly in the testa pericarp.     

Fructan contents and dry matter deposition in different tissues of the wheat grain during development

The role of fructan metabolism in the assimilate relations of the grain of wheat (Triticum aestivum L.) was investigated by determination of the dry matter and fructan content of grain components at short intervals during grain filling. During the initial phase of rapid expansion, most of the assimilates entering the grain were partitioned to the outer pericarp. A large fraction of these assimilates were used for the synthesis of fructan. Dry matter deposition and fructan synthesis in the outer pericarp ceased at about 5d after anthesis. At the same time, the endosperm and the inner pericarp and testa started to accumulate dry matter at a fast rate. This was also associated with significant fructan synthesis in the latter tissues. The outer pericarp lost about 45% of its former maximum dry weight between 9 and 19 d after anthesis. This loss was due almost entirely to the near complete disappearance of water-soluble carbohydrates, most of which was fructan. The inner pericarp and testa accumulated dry matter until about mid-grain filling. The fructan contents of the inner pericarp and testa and the endosperm decreased slowly towards the end of grain filling. Most of the fructans in the inner pericarp and testa and the endosperm had a low molecular weight, whereas higher molecular weight fructans predominated in the outer pericarp. The embryo did not contain fructan. The presence of low molecular weight fructans in the endosperm cavity at mid-grain filling was confirmed. It is suggested that fructan synthesis is closely linked to growth-related water deposition in the different tissues of the wheat grain and serves to sequester the surplus of imported sucrose.     

Electron-probe Microanalysis Studies of Silicon in the Epicarp Hairs of the Caryopses of Hordeum sativum Jess., Avena sativa L., Secale cereale L. and Triticum aestivum L.

Silicon deposits in the epicarp hairs of the caryopses of mature,field-grown specimens of Hordeum sativum, Avena sativa, Secalecereale and Triticum aestivum were investigated using electron-probemicroanalysis. In all four cereals, silicon was most concentratedat the extreme tips of the hairs. In barley, it was the onlyelement detected; in the other three cereals potassium and calciumwere located below the tip. In wheat, chlorine was also detected. The hair bases of the different cereals displayed variationin the elements detected. Silicon and polassium were presentin all four and calcium present in all except rye. The hairbases of wheat also contained chlorine; phosphorus and zincwere located in barley. The latter alone showed variation ofelements between hair bases. Scanning electron microscopy revealed heavy striations of thehair tips of barley and oats. In rye and wheat, the tips weresmooth but there were slight surface markings below the tip. The results are discussed in relation to the possible functionsand significance of the epicarp hairs and their silicification. Avena sativa L., Hordeum sativum Jess., Secale cereale L., Triticum aestivum L., oat, barley, rye, wheat, epicarp hairs, silicon, electron-probe microanalysis, scanning electron microscopy     

Photosynthesis and Transpiration in Leaves and Ears of Wheat and Barley Varieties

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 40–80%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 40–80% of total spikeCER, depending on the species, but only 10–20% 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     

Light-Dependent CO2 Retrieval in Immature Barley Caryopses

Immature detached caryopses from barley (Hordeum vulgare L.var. distichum cv. Midas) were shown to be capable of light-dependentretrieval of internally-produced CO₂. In the first set of experiments,caryopses were radioactively labelled by supplying (U-14C)-sucroseto detached ears in liquid culture. Caryopses were then removedfrom the ear and given a 12 h chase of non-radioactive sucrosein either the light or dark. More ¹⁴C was recovered in the caryopsesafter the chase in the light than in the dark but the differenceswere not significant. In the second set of experiments, ¹⁴C-labelledcaryopses obtained by a 15 min light incubation in ¹⁴CO₂ weremaintained in either the light or dark for 3 h and any redistributionof label between the tissues recorded. The results show thatunder these conditions, photosynthesis in the Chl-containinggreen layer of the pericarp can prevent losses of internally-producedCO₂, since 3 times as much radiocarbon remained in the caryopsesincubated in the light as in the dark. These differences weresignificant at P=0.001. Experiments with the mutant barley Albinolemma, which has no Chi in the pericarp, showed that there waslittle difference between light and dark treatments. This confirmsthe suggestion that photosynthesis in the pericarp of the normalcultivar Midas may be concerned in the refixation of CO₂. Key words: Barley, pericarp, photosynthesis, carbon dioxide     

Tissue-specific localization of aspartic proteinase in developing and germinating barley grains

Resting seeds of several plant species, including barley grains, have been reported to contain aspartic proteinase (EC 3.4.23) activity. Here, the expression of the Hordeum vulgare L. aspartic proteinase (HvAP) was studied in developing and germinating grains by activity measurements as well as by immunocytochemical and in-situ hybridization techniques. Southern blotting suggests the presence of one to two HvAP-encoding genes in the barley genome, while Northern analysis reveals a single 2.1-kb mRNA in grains and vegetative tissues. Western blotting with antibodies to HvAP shows the same subunit structure in different grain parts. In developing grains, HvAP is produced in the embryo, aleurone layer, testa and pericarp, but in the starchy endosperm HvAP is present only in the crushed and depleted area adjacent to the scutellum. During seed maturation, HvAP-encoding mRNA remains in the aleurone layer and in the embryo, but the enzyme disappears from the aleurone cells. The enzyme, however, remains in the degenerating tissues of the testa and pericarp as well as in resting embryo and scutellum. During the first three days of germination, the enzyme reappears in the aleurone layer cells but is not secreted into the starchy endosperm. The HvAP is also expressed in the flowers, stem, leaves, and roots of barley. The wide localization of HvAP in diverse tissues suggests that it may have several functions appropriate to the needs of different tissues.Abbreviations DAA days after anthesis - DTT dithiothreitol - HvAP Hordeum vulgare aspartic proteinase Both authors have contributed equally to this workWe thank Mart Saarma, Pia Runeberg-Roos, Alan Schulman and Yrjö Helariutta for helpful discussions during the study, Tiina Arna and Sari Makkonen for their help in proteinase activity experiments as well as Jaana Korhonen (Department of Pathology, University of Helsinki), Salla Marttila and Ilkka Porali (Department of Biology, University of Jyväskylä, Jyväskylä, Finland) for their advice on microscopical techniques. We also thank Liisa Pyhälä and Leena Liesirova for the production of the antibodies to HvAP at the National Public Health Institute, Helsinki. This study was supported by grants from the Ministry of Agriculture and Forestry and the Academy of Finland.     

Observations on the Germ Aleurone of Barley. Morphology and Histochemistry

The germ aleurone over the embryonic axis of barley was examinedin strips of tissue peeled off harvest-ripe grains. The germaleurone is only one cell thick but resembles 'normal' aleuronein being composed of living cells with dense, lipid-rich cytoplasmand thick walls containing phenolic material. In contrast tothe cells of the 'normal' aleurone, germ aleurone cells containvery few phytin or protein deposits. When the germ aleuroneis ruptured during germination, the walls at the torn edge becomethickened with shiny golden-brown material, and 'sealed' tothe testa. Two days after germination, lignin can be detectedin the walls of a single row of germ aleurone cells adjoiningthe scutellum. The role of the germ aleurone in defence againstmicroorganisms is discussed. It is suggested that the metabolicactivities in the germ aleurone in imbibed grains compete withthe embryo for oxygen, and thus may be one of the factors whichdetermine whether a grain germinates or remains dormant.Copyright1994, 1999 Academic Press Barley, Hordeum vulgare L., germ aleurone, histochemistry, defence mechanism, lignin, dormancy, microorganisms, pre-mature germination     

Male Sterility and Anther Wall Structure in Copper-deficient Plants

Anther development and pollen sterility were followed in plantsof wheat, oat, barley, sweetcorn, sunflower, petunia and subterraneumclover grown at a range of copper supplies. Copper-deficientplants had increased pollen sterility. Lignified wall thickenings were reduced or absent in the endotheciaof anthers from Cu-deficient plants. Reduced seed set may resultboth from reduced pollen fertility or failure of the stomiato rupture due to decreased lignification of anther walls. Triticum aestivum L., wheat, Hordeum vulgare L., barley, Avena sativa L., oat, Zea mays L., corn, sweetcorn, maize, Helianthus annuus L., sunflower, Petunia hybrida L., Trifolium subterraneum L., subterranean clover, male sterility, anther development, copper deficiency     

Studies on the Ultrastructure at the Interface of the Cotyledon and the Testa of Cashew Nut (Anacardium occidentale L.) Before and After Industrial Processing

A cuticle was found for the first time on the surface of theepidermis of the cotyledon of Anacardium occidentale L., andthe ultrastructure of the cuticle was established as being narrowand lamellate. The major ultrastructural features of the previouslyundescribed testa were the layers of crushed, lignified cellsin the endosperm layer, and an associated, electron-dense complexat the interface. Changes in the ultrastructure of the outerlamella of the cuticle, the sub-epidermal layer of the cotyledonand the lining complex of the testa were observed after removalof the testa by industrial processing. The basic ultrastructureof the endosperm layer of the testa and the inner lamella ofthe cuticle were found to be least affected by the processing.     

Effect of High Temperature During Grain-filling on the Structure of Developing and Malted Barley Grains

High temperatures (up to 35 °C) were applied to plants ofmalting barley,Hordeum vulgareL. (‘Schooner’) fora period of 5 d during grain-filling. Heat treatment had a profoundeffect on the structure of the mature barley grain. There wasevidence of degradation of endosperm storage products in heat-treatedgrain. Starch granule development was reduced in sub-aleuronecells following heat treatment and alterations to starch granuledistribution and growth were observed in the endosperms of thesegrains. Endosperm cell wall and crushed cell layer (CCL) developmentwere sensitive to high temperatures, with the reduced thicknessof the CCL and generally patchy Calcofluor fluorescence of endospermcell walls indicative of partial hydrolysis of ß-glucans.Increased growth of the embryo took place in heat-treated grainscompared with control grains. Endosperm texture was generallymore friable in heat-treated grains than in control grains,and these grains overmodified during malting, with considerabledegradation of starch in the form of extensive pitting of A-typestarch granules. Evidence is presented for developmental andgermination events occurring simultaneously within the developinggrain.Copyright 1998 Annals of Botany Company Barley,Hordeum vulgareL., starch granules, crushed cell layer, scutellum, embryo, fluorescence microscopy, scanning electron microscopy, confocal microscopy, malting quality.     

Structural and physiological characterization during wheat pericarp development

Key message

The cytological and physiological features of developing wheat pericarp were clearly characterized in this report. Our results may be helpful to articulate the functions of pericarp during the seed development.

Abstract

Although wheat pericarp has been well studied, knowledge of the sequence of events in the process of pericarp development is incomplete. In the present study, the structural development process of wheat (Triticum aestivum L.) pericarp was investigated in detail using resin microtomy and microscopy. Chlorophyll contents, and photosynthetic and respiratory rates, in pericarp were determined using spectrophotometer and an oxygen electrode, respectively. Mineral nutrient contents were also determined using scanning electron microscopy. The main results are as follows: (1) based on the structures and physiological characteristics observed, the developmental process of pericarp was divided into four stages, growth, formation, extinction and maturation stages, pericarp exhibited specific features at each stage. (2) Pericarp development differed in different parts, or varieties, of wheat. The dorsal pericarp had fewer starch grains and slower rates of apoptosis than the abdominal mesocarp. The cross cells in dorsal pericarp had an irregular outline. When compared with soft wheat cv. Yangmai 11, mesocarp cells in hard wheat cv. Xumai 30 had more starch grains, larger cell size and longer development duration. (3) The chlorophyll content, photosynthesis rate and respiratory rate in pericarp increased gradually, reaching a maximum about 16 days after anthesis, and later decreased continually. The photosynthetic rate in pericarp was lower than the respiration rate. (4) The contents of mineral elements in pericarp, such as calcium, zinc, iron and potassium were higher than those in the inner endosperm. The data indicate that wheat pericarp has many functions, e.g. protection, photosynthesis, mineral accumulation, synthesis and degradation of starch.     

Rapid Swelling of Pollen Grains in the Dehiscing Anther of Two-rowed Barley (Hordeum distichum L. emend. LAM .)

The role of rapid swelling of pollen grains in anther dehiscencein Hordeum distichum L. emend. L AM. and the mechanism of thisswelling were examined. Artificial opening of the floret inducedrapid swelling of pollen grains and thecae dehiscence. The thecadehisced as pollen grains became swollen and dehisced anthershad larger pollen grains than indehisced anthers. Septa in theanther segments dehisced as a result of water-induced pollenpressure. These results strongly support the theory that therapid swelling of pollen grains is a driving force for antherdehiscence. On the other hand, potassium was detected in pollengrains from dehisced anthers, but not in pollen grains in indehiscedanthers. This suggests that potassium ions function as a turgorregulator in the rapid swelling of pollen grains. The mechanismof anther dehiscence is discussed in relation to the swellingof pollen grains, as is the possible mechanism of this swelling.Copyright 2000 Annals of Botany Company Anther dehiscence, Hordeum distichum L. emend. L AM., pollen swelling, potassium ion, two-rowed barley     

Development of the Almond Nut (Prunus dulcis (Mill.) D. A. Webb). Anatomy and Chemical Composition of Fruit Parts from Anthesis to Maturity

The growth of the fruit of two varieties of almond (Prunus dulcis(Mill.) D. A. Webb) was studid from anthesis (week 0) to maturity(week 32). The dimensions, fresh weight, moisture content, anatomyand chemical composition of the pericarp, testa, embryo, endospermand nucellus are recorded diagrarnmatically, graphically andby micrographs for one variety. Of the two ovules present atflowering only one normally developed further. By 12 weeks afterflowering the whole fruit had reached full size. The space encloscdby the pericarp was filled by nuallus until weck 10, with subsequentenlargement of both endosperm and embryo. From week 16 to week20 the embryo increased to full size with a concumnt decreasein the size of the endosperm. Sixteen weeks after flowering,the embryo began to accumulate protein and lipid, little ofwhich originated from either the nucellus or endosperm. Theembryo contained no starch or reducing sugar but up to 3% sucrosein the early stags which dtcreascd as lipid and protein increased.Starch and sucrose levels were high in the testa at week 16but subsbquently dropped, starch more rapidly than sucrose.The role of the testa in transport of metabolites to the embryois discussed. Prunus dulcis, almond, fruit development, anatomy, embryo, endosperm     

Ethylene Production by Fe-deficient Roots and its Involvement in the Regulation of Fe-deficiency Stress Responses by Strategy I Plants

Species that showed marked morphological and physiological responsesby their roots to Fe-deficiency (Strategy I plants) were comparedwith others that do not exhibit these responses (Strategy IIplants). Roots from Fe-deficient cucumber (Cucumis sativusL.‘Ashley’), tomato (Lycopersicon esculentumMill.T3238FER) and pea (Pisum sativumL. ‘Sparkle’) plantsproduced more ethylene than those of Fe-sufficient plants. Thehigher production of ethylene in Fe-deficient cucumber and peaplants occurred before Fe-deficient plants showed chlorosissymptoms and was parallel to the occurrence of Fe-deficiencystress responses. The addition of either the ethylene precursorACC, 1-aminocyclopropane-1-carboxylic acid, or the ethylenereleasing substance, Ethephon, to several Fe-sufficient StrategyI plants [cucumber, tomato, pea, sugar beet (Beta vulgarisL.),Arabidopsis(Arabidopsis thaliana(L.) Heynh ‘Columbia’), plantago(Plantago lanceolataL.)] promoted some of their Fe-deficiencystress responses: enhanced root ferric-reducing capacity andswollen root tips. By contrast, Fe-deficient roots from severalStrategy II plants [maize (Zea maysL. ‘Funo’), wheat(Triticum aestivumL. ‘Yécora’), barley (HordeumvulgareL. ‘Barbarrosa’)] did not produce more ethylenethan the Fe-sufficient ones. Furthermore, ACC had no effecton the reducing capacity of these Strategy II plants and, exceptin barley, did not promote swelling of root tips. In conclusion,results suggest that ethylene is involved in the regulationof Fe-deficiency stress responses by Strategy I plants.Copyright1999 Annals of Botany Company. Arabidopsis (Arabidopsis thaliana(L.) Heynch), barley (Hordeum vulgareL.), cucumber (Cucumis sativusL.), ethylene, iron deficiency, maize (Zea maysL.), pea (Pisum sativumL.), plantago (Plantago lanceolataL.), ferric-reducing capacity, sugar beet (Beta vulgarisL.), tomato (Lycopersicon esculentumMill.), wheat (Triticum aestivumL.).     

Comparative mapping of HKT genes in wheat, barley, and rice, key determinants of Na+ transport, and salt tolerance

Salt tolerance of plants depends on HKT transporters (High-affinityK⁺ Transporter), which mediate Na⁺-specific transport or Na⁺-K⁺co-transport. Gene sequences closely related to rice HKT geneswere isolated from hexaploid bread wheat (Triticum aestivum)or barley (Hordeum vulgare) for genomic DNA southern hybridizationanalysis. HKT gene sequences were mapped on chromosomal armsof wheat and barley using wheat chromosome substitution linesand barley–wheat chromosome addition lines. In addition,HKT gene members in the wild diploid wheat ancestors, T. monococcum(A^m genome), T. urartu (A^u genome), and Ae. tauschii (D^t genome)were investigated. Variation in copy number for individual HKTgene members was observed between the barley, wheat, and ricegenomes, and between the different wheat genomes. HKT2;1/2-like,HKT2;3/4-like, HKT1;1/2-like, HKT1;3-like, HKT1;4-like, andHKT1;5-like genes were mapped to the wheat–barley chromosomegroups 7, 7, 2, 6, 2, and 4, respectively. Chromosomal regionscontaining HKT genes were syntenic between wheat and rice exceptfor the chromosome regions containing the HKT1;5-like gene.Potential roles of HKT genes in Na⁺ transport in rice, wheat,and barley are discussed. Determination of the chromosome locationsof HKT genes provides a framework for future physiological andgenetic studies investigating the relationships between HKTgenes and salt tolerance in wheat and barley. Key words: Barley, comparative mapping, HKT, rice, salt tolerance, sodium transport, wheat     

Silicon Deposition in the Roots of Hordeum sativum Jess, Avena sativa L. and Triticum aestivum L.

Electron-probe microanalysis was used to investigate the locationof silicon at the proximal end of the seminal and adventitiousroots, of almost mature field-grown specimens of Hordeum sativumJess., Avena sativa L. and Triticum aestivum L. In the seminal roots silicon was confined to the endodermis,where it was present in the thickened inner tangential and radialwalls. The outer tangential walls also contained silicon inall of the cells in wheat and in occasional cells in barleyand oats. The adventitious roots of the three cereals displayed differencesin silicon deposition. In barley, silicon was present in allthe walls of the endodermal cells, whereas in oats it was onlylocated in the inner tangential and radial walls. Wheat showedcultivar differences, no silicon was detected in Capelle Desprez,but it was present in the thickened endodermis of Little Jossand Hustler. In all the samples studied silicon was absent fromthe sub-epidermal sclerenchyma layer. The results are discussed in relation to the possible functionsof the endodermis and the signficance of silicification. Hordeum sativum Jess, barley, Avena sativa L, oat, Triticum aestivum L, wheat, silicon deposition, electron-probe microanalysis     

Seed Dormancy in Acer pseudoplatanus L.: the Role of the Covering Structures

The present studies with Acer pseudoplatanus L. suggest thatthe covering structures play an important and multiple rolein the dormancy of the fruit. Whole fruits and seeds with thetesta intact required a period of chilling at 5 °C beforedormancy was broken whereas bare embryos germinated immediatelyat 20 °C without pretreatment. This suggested that dormancywas coat-imposed and that the testa was responsible for thiseffect. Germination of dormant seeds was inhibited by lightwhereas the non-dormant bare embryos showed little response.Studies on the manner in which the testa imposed dormancy onthe embryo indicated that restriction on oxygen uptake, wateruptake, mechanical restriction to embryo enlargement, and thepresence of germination inhibitors in the testa were not limitingfactors at this stage of dormancy. Results from leaching experimentssuggest that dormancy was the result of the restriction by thetesta of the outward diffusion of a germination inhibitor(s)present in the embryo. In seeds that had nearly completed theirstratification requirements, the covering structures seemedto act in a manner other than by preventing the leaching ofan inhibitor from the embryo. At this point the physical propertiesof the covering structures seem to determine any further delaysin germination by the mechanical restriction of embryo enlargementby the testa and by restriction of oxygen uptake by the pericarp.     

Genotypic effects of the maternal tissues of wheat on its grain weight

Summary Reciprocal crosses were made between semi dwarf spring wheat cultivars (Triticum aestivum L.) differing in grain weight. The weights of the F₁ grains (on maternal spikes), from intact as well as from defoliated plants, and those of the F₂ grains (on f₁ spikes), were examined. Grain weight was controlled primarily by the genotype of the maternal tissues (pericarp, testa or other floret or spikelet organs, including the vascular system), with complete dominance of heaviness. No indications suggesting maternal inheritance were obtained. The frequency distribution of the weights of the F₂ grains indicated the presence of genotypic effects exerted by the endosperm or embryo. The embryo or endosperm factors for heaviness also seemed to be dominant.This study is based on data obtained by the senior author in his Ph. D. research at The Hebrew University of Jerusalem. The research was financed in part by The Fund for the Encouragement of Research — Histadrut — The General Federation of Labor in Israel. Contribution from the Agricultural Research Organization, Bet Dagan, Israel. No. 173-E, 1980 series     

Studies on the Ultrastructure and Histochemistry of Plant Cuticles: The Cuticular Membrane of Agave americana L. in situ

The outer epidermal wall of Agave americana leaves was examinedin order to gain more information about the location and chemicalconstitution of the structural components. In middle aged leavesthe wall comprised six layers which were designated epicuticularwax, cuticle proper, exterior and interior cuticular layer,exterior and interior cellin wall. A lamellated structure, consistingof a series of electron translucent lamellae of uniform thicknessalternating with opaque ones of variable thickness, was observedin the thin cuticle proper on the outside of the cuticular membrane,even without heavy metal treatment. The cuticular layers underneathformed the bulk of the cuticular membrane and they also hadtwo components, an amorphous matrix permeated by a reticulumof fibrillae. Cutin, detected with osmium and with iodine/iodine-sulphuricacid–silver proteinate, was a major component of the opaquelamellae of the cuticle proper and the matrix of the cuticularlayer. Carbohydrates were absent from the cuticle proper butwere detected specifically in the fibrillae of the cuticularlayer and in the cellin wall. Pectic material seemed to be presenton both sides of the junction between cuticular membrane andcellin wall, but no discrete zone corresponding to light microscopicalobservations was detected in the electron microscope. Althoughthe lucent lamellae of the cuticle proper were tentatively ascribedto wax there was no structural or ultrahistochemical evidencefor the wax component of the cuticular layer. The various ultrahistochemicalreactions are discussed in relation to the known chemical compositionof the membrane. Agave americana L., epidermis wall, cuticular membrane, cuticle proper, cuticular layer, ultrahistochemistry, wax     

在高CO2浓度下生长的小麦对棉铃虫生长发育和繁殖的影响

通过室内饲养实验研究了在高CO₂浓度（738.8±25.7μL/L）中生长的小麦对棉铃虫 Helicoverpa armigera (Hübner)生长发育,繁殖以及营养效应的影响。结果表明： （1）取食高CO₂浓度大气中生长的麦粒的棉铃虫对食料的取食量和粪便排泄量增加,与对照相比,取食量和粪便排泄量分别增加46.3%（P<0.05）和37.8%;（2）大气CO₂浓度增加影响了麦粒中的营养成分的含量,其中,可溶性蛋白、游离氨基酸、葡萄糖和总糖的含量及碳氮比(C∶N)都显著增加,果糖和粗蛋白的含量都显著降低;（3）大气 CO₂浓度升高所导致的麦粒营养成分的变化影响了棉铃虫幼虫的食物利用效率,与对照组相比,棉铃虫幼虫对食物的毛转化率和净转化率分别降低27.2%和25.4%,对食物的相对取食率则显著提高58.8%（P < 00.1）。据此推测,未来高CO₂浓度的大气环境会降低春小麦的营养价值,从而影响棉铃虫的生长发育,加重其对小麦的危害。