Lactic acid content and formation in pea roots exposed to salinity

Lactic acid content and production, as well as lactic dehydrogenaseactivity were studied in pea root tips grown in media salinatedwith NaCl or Na₂SO₄. Salinity of both types depressed the lacticacid content of the tissue. Lactic dehydrogenase activity linkedto NADH was depressed by high concentrations of NaCl in thegrowth medium, but was stimulated by increasing concentrationsof Na₂SO₄. There was a trace of NADPH linked activity of theenzyme; this activity was not affected by chloride salinitybut was depressed by sulphate salinity. It is not yet clearhow these events are connected with the overall effect of salinityon the carbohydrate metabolism of pea root tips. (Received June 27, 1970; )     

The effect of salinity on glucose absorption and incorporation by pea roots

Osmotic adaptation was observed in pea plants grown in Na₂SO₄salinized media but no complete adaptation was observed in plantsgrown in NaCl salinized media. The absorption of externally supplied glucose was depressedin pea root tips from plants grown in media salinized with eitherNaCl or Na₂SO₄. Under NaCl salinity this depression increasedwith increasing salinity. Under Na₂SO₄ salinity, no significantinhibition of absorption was observed in roots exposed to waterpotentials higher than –5 atmosphere. The amount of ¹⁴Creleased as CO₂, expressed as the percent of absorbed ¹⁴C, increasedwith increasing salinity of both types. In roots grown underNaCl salinity, the incorporation of ¹⁴C into ethanol non-soluble,acid hydrolyzable substances was markedly inhibited. This inhibitionwas increased by increasing the external salinity. The effectof Na₂SO₄ salinity was similar but not so pronounced. The incorporation of ¹⁴C from externally supplied glucose intothe alkali-soluble fraction was practically uneffected by salinity.Non-extractable ¹⁴C was decreased in roots exposed to NaCl butwas not, apparently, effected by Na₂SO₄). Because of the smallnessof this fraction no clear cut conclusion can be made. Possiblemechanisms for the events are discussed. (Received October 26, 1972; )     

Regulation of Inflorescence Growth in Cuttings of the Grape Vine (Vitis vinifera L.)

In woody cuttings of the grape vine inflorescences of fertilebuds usually atrophy soon after bud burst. Inflorescences areretained if leaves are removed from the elongating shoot, butremoval of apices and roots does not affect inflorescence growthif leaves are present. With defoliated cuttings, inflorescencegrowth is stimulated by removal of apices but depressed by removalof roots. Applications of indole acetic acid to the petiolestumps of defoliated cuttings did not replace the effect ofleaves and induce atrophy of inflorescences. Inflorescence growthin defoliated cuttings was inhibited by 2,4-dichlorophenoxyaceticacid (2,4-D), but concentrations which depressed inflorescencegrowth produced toxicity symptoms. Applications of 2,3,5-tri-iodobenzoicacid to petioles and leaf laminae were without effect on inflorescencegrowth. Treatment of inflorescences with the cytokinin 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine(SD 8₃₃₉) promoted inflorescence growth in both the presenceand the absence of leaves. Inhibitory effects of 2,4-D on inflorescencegrowth were partially reversible by application of SD 8₃₃₉.Response of inflorescences to gibberellic acid required eitherremoval of leaves or addition of SD 8₃₃₉.     

Persistence of Modifications Induced by Osmo-saline Shocks on Chloride Transport and Some Related Metabolic Processes in Roots of Maize Plants

Excised roots obtained from maize plants, previously treatedfor 24 h with different solutes (K₂SO₄, Na₂SO₄, or mannitol)at decreasing osmotic potential values, showed clearly the persistenceof osmo-saline shock in their chloride transport and in somemetabolic processes. In particular, vacuolar accumulation ofchloride was much reduced when the osmotic potential in pretreatmenthad been low; this effect was greater with solutions of electrolytes.Protein synthesis and [¹⁴C]leucine uptake were also reduced;thus there appeared to be a correlation between chloride accumulationin the vacuole and protein synthesis. By contrast, accumulationof chloride in the cytoplasm was only slightly modified or evenstimulated. Chloride influx was affected less by osmotic pretreatmentthan accumulation, except in the case of very low osmotic potentialswhere influx was depressed. Chloride efflux was slightly enhancedby osmo-saline shocks and the fluxes at the tonoplast were lessaffected in comparison with those at the plasmalemma. Malateaccumulation was stimulated by shock, but this effect was notpersistent, so that a correlation with the effects on accumulationand fluxes was not possible. Oxygen uptake was affected onlyslightly except that at osmotic potential values of –750kPa, perhaps because of a lowered viability of the roots subjectedto very low osmotic potential for 24 h.     

Photosynthesis and Osmotic Adjustment of Two Sugarbeet Cultivars Grown under Saline Conditions1

The response of photosynthesis in two sugarbeet cultivars exposedto 180 mol m^–3 NaCl was investigated. An increase in photosynthesis was found in both cultivars duringthe initial 4 d after exposure to salinity. With longer timeperiods, CO₂ fixation in one cultivar, Monriac, was not affected,while under the same conditions, photosynthesis of the othercultivar, Kawemegapoly, was significantly reduced. Full osmoticadjustment was obtained in both cultivars, and the sensitivityof Kawemegapoly to salinity was not due to loss of turgor. Thepossible mechanisms responsible for this phenomenon are discussed.Rubisco activity responded to salinity as CO₂ fixation ratein both cultivars. Key words: Photosynthesis, osmotic adjustment, salinity     

Carbon Partitioning in Split Root Systems of Barley: The Effect of Osmotica

Vegetative barley plants, grown with their root systems splitbetween two containers, were supplied with ¹¹CO₂ to the secondleaf. Both halves of the split root were monitored separatelywith scintillation detectors and a pre-treatment value for partitioningbetween them established. Mannitol or sorbitol was added tothe medium around one root-half to lower the solute potentialto –0?4 MPa, and partitioning of C-11 between the tworoot halves was followed continuously for 3 h. Alternatively,¹⁴CO₂ was supplied at, or 3 h or 24 h after, treatment withosmotica, and roots were harvested and counted 3 h later. Osmoticarapidly increased the import of isotope into the treated root-half,but this effect and a respiratory increase induced by the osmoticawas transient. Within 3 h of applying the osmoticum, partitioningbetween the root halves was little affected. Slow addition ofosmotica (0?12 MPa h^–1) did not affect partitioning betweenroot halves. We conclude that the solute potential of the apoplastcan have a major if transient effect on carbon partitioningbut that this is unlikely to be important in vivo as osmoregulationby the root can negate its effects. Key words: Carbon partitioning, barley, osmotica, split-root system     

The Effect of Salinity on Light and Dark CO2-Fixation of Salt-Adapted and Unadapted Cell Cultures of Atriplex and Tomato

The effect of salinity on light and dark CO₂,-fixation was determinedin cells of A triplex portulacoides and tomato (Lycopersiconesculenturn Mill.) grown in culture. CO₂,-fixation of tomatocells was also determined in cultures adapted to mannitol andpolyethylene glycol (PEG). Salinity up to 400 mM NaCI in thecase of A triplex and up to 50 mM in the case of tomato enhancedthe rate of light-induced CO₂,-flxation in unadapted cells.Higher salt concentrations led to a marked decline in CO₂-flxationin both species. In salt-adapted A triplex cells no declinein the rate of light CO²,-flxation was seen even at 500 mM NaCl.Dark CO₂,-fixation was approximately 40% and 80% of the lightfixation in control cell cultures of A triplex and tomato, respectively.No enhancement in dark CO₂,-flxation was seen as salinity wasincreased, but a decline was found at similar salt concentrationsthat decreased fixation in the light. Mannitol-and PEG-adaptedtomato cells fixed CO₂, at somewhat lower rates than the controlcells in the light but not in the dark. Key words: Salinity, CO₂-fixation, cell cultures, Atriplex, tomato     

Changes in the Water Balance and Photosynthesis of Onion, Bean and Cotton Plants under Saline Conditions

The osmotic concentration (osmotic potential) of onion leaf sap did not adjust to chloride salinity, and consequently water potential, turgor, stomatal aperture and transpiration were reduced. Although osmotic concentration of bean and cotton leaf sap did adjust to a saline root medium and turgor was no less in the salinized plants than in the controls, stomata of the salinized plants remained only partly open and transpiration was reduced. Net photosynthesis of onion plants was reduced by salinity (this effect being much enhanced in a hot dry atmosphere) but it could be rapidly raised to the level of the controls by inducing elevated leaf turgor. Stomatal closure was initially responsible for most of the ～30 % reduction in photosynthesis of salinized beans. This was due to interference with CO₂ diffusion and could be overcome by raising the CO₂ concentration in the air. At a later stage of growth, salinity affected the light reaction of bean photosynthesis, and elevation of the air CO₂ had little effect. Closure of stomata of salinized cotton plants had only a relatively small effect on net photosynthesis. Light intensity and CO₂ concentration experiments showed that salinity was reducing the photosynthesis of cotton leaves mainly by affecting the light reaction of photosynthesis. It is concluded that chloride salinity does affect the water balance and rate of photosynthesis of plants and that the nature and degree of the effects will depend upon climatic conditions and may be very different between plant species and in the same species at different periods of growth.     

Mechanical properties of spruce and beech wood grown in elevated CO2

Biomechanical responses of stems of 6- to 7-year-old spruce [Picea abies (L.) Karst.] and beech (Fagus sylvatica L) trees were studied after 4 years of growth in elevated atmospheric CO₂ in combination with a nitrogen treatment and on two different soil types. At the end of the treatment, stems were harvested and tested in fresh and air-dried status. Bending characteristics of juvenile wood (modulus of elasticity, termed rigidity) were determined by bending tests. Fracture characteristics (termed toughness) were determined by stroke-pendulum tests. From the base disk of each stem densitometric data were obtained. In spruce, wood produced under elevated CO₂ was tougher on both soil types; enhanced N deposition made wood less rigid only on acidic soils. In contrast, beech wood samples showed no significant reaction to CO₂ but were significantly tougher under high nitrogen depositions on acidic soil. Effects on wood density of both CO₂ and N treatments were not significant, but wood density was higher on acidic soil and so were rigidity and toughness (soil effect). Different genotypes of spruce and beech reacted significantly differently to the treatments. Some genotypes reacted strongly to CO₂ or N, whereas others did not react or showed interactions between CO₂ and N. This underlines the importance of genetic diversity in tree communities.     

The effect of CO2 on ethylene evolution and elongation rate in roots of sunflower (Helianthus annuus) seedlings

Both carbon dioxide and ethylene can affect the rate of root elongation. Carbon dioxide can also promote ethylene biosynthesis by enhancing the activity of 1-aminocylopropane-1-carboxylic acid (ACC) oxidase. Since the amount of CO₂ in the soil air, and in the atmosphere surrounding roots held in enclosed containers, is known to vary widely, we investigated the effects of varying CO₂ concentrations on ethylene production by excised and intact sunflower roots (Helianthus annuus L. cv. Dahlgren 131). Seedlings were germinated in an aeroponic system in which the roots hung freely in a chamber and were misted with nutrient solution. This allowed for treatment, manipulation and harvest of undamaged and minimally disturbed roots. While exposure of excised roots to 0.5% CO₂ could produce a small increase in ethylene production (compared to roots in ambient CO₂), CO₂ concentrations of 2% and above always inhibited ethylene evolution. This inhibition of ethylene production by CO₂ was attributed to a reduction in the availability of ACC: however, elevated CO₂ had no effect on ACC oxidase activity. ACC levels in excised roots were depressed by CO₂ at a concentration of 2% (as compared to ambient CO₂), but n-malonyl-ACC (MACC) levels were not affected. Treating intact roots with 2% CO₂ inhibited elongation by over 50%. Maximum inhibition of elongation occurred 1 h after the CO₂ treatment began, but elongation rates returned to untreated values by 6 h. Supplying these same intact roots with 2% CO₂ did not alter ethylene evolution. Thus, in excised sunflower roots 2% CO₂ treatment reduces ethylene evolution by lowering the availability of ACC. Intact seedlings respond differently in that 2% CO₂ does not affect ethylene production in roots. These intact roots also temporarily exhibit a significantly reduced rate of elongation in response to 2% CO₂.     

Regulation of Sulphate Transport in a Tropical Legume, Macroptilium atropurpureum, cv. Siratro

When young plants of Macroptilium atropurpureum, cv. Siratrowere deprived of external sulphate (-S plants) growth of shootsand roots continued at rates comparable to those in plants wellsupplied with sulphate (control) for 3 d and 5 d respectively.Dilution of internal sulphur therefore took place and redistributionof sulphur occurred between inorganic and organic forms andbetween roots and younger leaves. Even when S-deficiency limitedgrowth, plants contained 16% of their total sulphur as sulphate,but most of this was retained in old leaves and redistributedslowly to growing zones. The capacity for sulphate uptake increased in roots of –Splants very soon after they were deprived of external sulphate;within 24 h the absorption from 0.25 mol m^–3 SO₄^2–was more than five times that of control roots. Maximum increasedcapacity was reached after 2–3 d stress when the V_maxof system 1 was 1948 nmol h^–1g^–1root fr. wt. in–S plants and 337 nmol h^–1g^–1root fr. wt.in controls. The K^mfor system 1 did not change significantlywith S-stress being between 5–8 µM in both setsof plants. Absorption of L-cysteine was not stimulated by S-stress. There was a close, positive relationship between plant growthrate and the rate at which sulphate uptake capacity was enhancedby withholding sulphate from culture solutions. When –S plants were replaced in sulphate-containing solutiontheir capacity for SO₄^2– declined to the control levelwithin 24 h. Very marked repression of capacity was also foundwhen –S plants were treated with L-cysteine, but therewas no immediate effect with methionine. Roots of this species appear to have a very active system fordegrading L-cysteine to sulphate, 30% of the label in ³⁵S-cysteineabsorbed by roots was recovered in ³⁵SO₄^2– after 20 minor 2 h incubation. By contrast, roots had a very weak abilityto reduce sulphate. When part of the root system was in solution lacking sulphatethere was enhanced uptake of sulphate by other parts which themselveswere amply supplied with sulphate. This is seen as an exampleof compensatory absorption. The response to S-stress is specific and there were no positiveinteractions between S-stress and the absorption of phosphate,or P-stress and the uptake of sulphate. The results are discussed in relation to the close control ofsulphate uptake by internal sulphate concentration, redistributionof forms of sulphur during stress and mobility of sulphate inthe phloem. Key words: Kinetics, Amino-S, Sulpholipid, Repression;, Deficiency     

The Labelling of Glucose-6-phosphate in Pea Slices Supplied with 14C Glucose, and the Assessment of the Respiratory Pathways in Air, in 10% CO2 and in 2% O2 in N

A method is proposed for estimating the proportion of CO₂ ofrespiration derived from the PPP and the TCAC by measuring thespecific activity of the respired CO₂ and those of its precursorsin the tissue. In practice the specific activity of C-1 of G-6-Pand of the carboxyl carbon atoms of pyruvate and malate havebeen taken as the precursors. To apply this method there mustbe good evidence that these compounds are not in ‘pools’in the cell. In air in the sliced pea cotyledon 25–40% of the respiredCO₂ arose from the PPP. In both 10% CO₂ in air and in 2% O₂ in N there was a showingin the rate of respiration and a large increase in the proportionof the CO₂ deriving from the PPP. It is argued that in eachcase the cause of this was different. Key words: Carbon dioxide, Respiration, Pisum Sativum, Pentose-phosphate pathway     

Effect of substrate salinity on the ability for protein synthesis in pea roots

The effect of salinity on incorporation of amino acids into root tip protein is apparently of dual nature: in presence of salts the uptake is depressed and the normal metabolic pathways are disturbed. If the roots were grown at high salt concentration, uptake and incorporation are affected even if they are carried out in the absence of salt. NaCl and Na₂SO₄ affect uptake, incorporation, and metabolism of ¹⁴C leucine in different ways. There are also preliminary indications that in pea roots grown at different types of salinity, different proteins may be synthesized. Kinetin was found to inhibit incorporation of amino acids into non stressed and Na₂SO₄ stressed roots, but promotes uptake and incorporation of amino acids into protein in NaCl stressed tissue. It seems that there are some pronounced differences between the effects of NaCl and Na₂SO₄ salinities on the metabolism of pea root tissue.     

The Effects of CO2 Enrichment and Nutrient Supply on Growth Morphology and Anatomy of Phaseolus vulgaris L. Seedlings

Plants of Phaseolus vulgaris were grown from seed in open-topgrowth chambers at the present (P, 350 µmol mol^–1)atmospheric CO₂ concentration and at an elevated (E, 700 µmolmol^–1) CO₂ concentration, and at low (L, without additionalnutrient solution) and high (H, with additional nutrient solution)nutrient supply for 28 d The effects of CO₂ and nutrient availabilitywere examined on growth, morphological and biochemical characteristics Leaf area and dry mass were significantly increased by CO₂ enrichmentand by high nutrient supply Stomatal density, stomatal indexand epidermal cell density were not affected by elevated CO₂concentration or by nutrient supply Leaf thickness respondedpositively to CO₂ increasing particularly in mesophyll areaas a result of cell enlargement Intercellular air spaces inthe mesophyll decreased slightly in plants grown in elevatedCO₂ Leaf chlorophyll content per unit area or dry mass was significantlylower in elevated CO₂ grown plants and increased significantlywith increasing nutrient availability The content of reducingcarbohydrates of leaves, stem, and roots was not affected byCO₂ but was significantly increased by nutrient addition inall plant parts Starch content in leaves and stem was significantlyincreased by elevated CO₂ concentration and by high nutrientsupply Phaseolus vulgaris, elevated atmospheric CO₂, CO₂-nutrient interaction, stomatal density, leaf anatomy, chlorophyll, carbohydrates, starch     

Sulphate supply and its regulation of transport in roots of a tropical legume Macroptilium atropurpureum cv. Sirato

During a period of sulphate deprivation, roots of Macroptiliumatropurpureum responded by increasing their uptake capacityat the plasma membrane. This effect was apparent both in intactplants and in tissues excised prior to uptake. In experiments using excised root systems previousy labelledwith ³⁵SO₄^2- the rate of tracer transport to the xylem was muchgreater in roots subsequently deprived of external sulphatethan in those supplied with unlabelled sulphate. Removing theexternal sulphate to the external solution. Additionally, compartmentalanalysis of tracer exchange kinetics showed that the flux ofsulphate from the cytoplasm to the xylem(     

Chemical Characteristics of Grains of Rice (Oryza sativa L.) Cultivated in Saline Media of Varying Ionic Composition

Two varieties of rice (Oryza sativa L.), Pokkali (salt-tolerant)and IR5929-12-3 (salt-sensitive), were grown in media of varyingionic composition namely chloride-sulphate (with sulphate dominant),sulphate-chloride (with chloride dominant) and chloride. Eachsalinity type had four different levels (expressed as electricalconductance) 2, 4, 6 and 8 dS m^–1. Amylose content ofthe endosperm, gelatinization temperature of the endosperm starch,brown rice protein content and the Na content of the hull andmilled rice showed that different salinity types affect thesecharacteristics differently. The greater Na accumulation inthe hull than in the milled rice in both varieties is presumedto be an adaptive response to salinity. Key words: Salinity, ionic compositions, rice grain.     

Chloroplast ultrastructure of sugar beet (Beta vulgaris L.) cultivated in normal and elevated CO2 concentrations with two contrasted nitrogen supplies

Sugar beet (Beta vulgaris L., cultivar Celt) plants were grownunder simulated field conditions in pots and supplied with adequateor deficient nitrogen (HN and LN, respectively) combined withtwo CO₂ concentrations, ambient (c. 350µmol mol^–1C0₂—AC), or elevated CO₂ (c. 600 µmol mol^–1CO₂—HC). Chloroplast structure in mesophyll palisade cellsof mature leaves (leaf number 19 in HN and 9 in LN), sampledat midday on 16 August 1993 was studied by transmission electronmicroscopy and quantified stereologically. The ultrastructureof palisade parenchyma chloroplasts was affected by the elevatedCO₂ concentration and strikingly affected by nitrogen supply.Chloroplast diameter (cross-sectional length) was slightly,but not significantly, greater in HC than AC treatments withinan N treatment, but was smaller in LN than HN; chloroplast cross-sectionalarea also increased with HC in both N treatments, but only significantlyso in LN. Elevated CO₂ reduced the proportion of total thylakoids(significant at 5% and 0.1% in HN and LN, respectively) dueto decreased granal thylakoids, but the proportion of inter-granal(stromal) thylakoid membranes was not affected compared to chloroplastsfrom plants grown with ambient CO₂. Chloroplast stroma increasedas a proportion of chloroplast volume with elevated comparedto ambient CO₂ with HN but not LN. Starch inclusions were notsignificantly different with elevated compared to ambient CO₂at HN, but the proportion of starch increased considerably atelevated compared to ambient C0₂ at LN, indicating an over-productionof assimilates. Plastoglobuli in chloroplasts increased withdeficient N, but decreased with elevated CO₂. Larger chloroplastswith a greater proportion of stroma, but a smaller proportionof granal thylakoids, suggest increased CO² assimilating capacityand decreased light harvesting/PSII capacity with elevated CO₂. Key words: Chloroplast, ultrastructure, elevated CO₂ concentration, nitrogen deficiency, sugar beet, Beta vulgaris     

Interactive effects of mycorrhization and elevated atmospheric CO2 on sulphur nutrition of young pedunculate oak (Quercus robur L.) trees

Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO₂ concentration and 650 μmol mol^?1 CO₂ in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 22 weeks under nonlimiting nutrient conditions. Sulphate uptake, xylem loading and exudation were analysed in excised roots. Despite a relatively high affinity for sulphate (K_M= 1.6 mmol m^?3), the rates of sulphate uptake by excised lateral roots of mycorrhizal oak trees were low as compared to herbaceous plants. Rates of sulphate uptake were similar in mycorrhizal and non-mycorrhizal roots and were not affected by growth of the trees at elevated CO₂. However, the total uptake of sulphate per plant was enhanced by elevated CO₂ and further enhanced by elevated CO₂ and mycorrhization. Sulphate uptake seemed to be closely correlated with biomass accumulation under the conditions applied. The percentage of the sulphate taken up by mycorrhizal oak roots that was loaded into the xylem was an order of magnitude lower than previously observed for herbaceous plants. The rate of xylem loading was enhanced by mycorrhization and, in roots of mycorrhizal trees only, by growth at elevated CO₂. On a whole-plant basis this increase in xylem loading could only partially be explained by the increased growth of the trees. Elevated CO₂ and mycorrhization appeared to increase greatly the sulphate supply of the shoot at the level of xylem loading. For all treatments, calculated rates of sulphate exudation were significantly lower than the corresponding rates of xylem loading of sulphate. Radiolabelled sulphate loaded into the xylem therefore seems to be readily diluted by unlabelled sulphate during xylem transport. Allocation of reduced sulphur from oak leaves was studied by flap-feeding radiolabelled GSH to mature oak leaves. The rate of export of radioactivity from the fed leaves was 4–5 times higher in mycorrhizal oak trees grown at elevated CO₂ than in those grown at ambient CO₂. Export of radiolabel proceeded almost exclusively in a basipetal direction to the roots. From these experiments it can be concluded that, in mycorrhizal oak trees grown at elevated CO₂, the transport of sulphate to the shoot is increased at the level of xylem loading to enable increased sulphate reduction in the leaves. Increased sulphate reduction seems to be required for the enhanced allocation of reduced sulphur to the roots which is observed in trees grown at elevated CO₂. These changes in sulphate and reduced sulphur allocation may be a prerequisite for the positive effect of elevated CO₂ on growth of oak trees previously observed.     

Dormancy in Cereal Seeds: II. THE NATURE OF THE GASEOUS EXCHANGE IN IMBIBED BARLEY AND RICE SEEDS

When barley seeds imbibe water, the O₂ uptake of non-dormantseeds is considerably less than that of dormant seeds for atleast the first 6 h, irrespective of the rate at which the seedshad previously lost dormancy. During the initial 6 h of imbibition, the CO₂ output of dormantbarley seeds is usually only slightly greater than and sometimesno different from that of nondormant seeds. The CO₂ output ofdormant seeds is reduced by about 66 percent by millimolar KCN,whereas that of non-dormant seeds is decreased by about 12–13per cent only. The CO₂ output of dormant barley in nitrogenis considerably less than the CO₂ output of non-dormant seedsunder the same conditions. Dormant rice seeds also show a higher initial O₂ uptake thannon-dormant seeds, though this is not generally as marked asin barley. Similarly, the initial CO₂ output of dormant seedsis distinctly greater than that of non-dormant seeds, but inmillimolar KCN it is depressed to a greater extent than in non-dormantseeds. In nitrogen, the CO₂ outputs of dormant and non-dormantseeds were found to be the same. Consequently, unlike barley,dormant rice seeds appear to be as capable of carrying out alcoholicfermentation under anaerobic conditions as nondormant seeds. In barley, increasing the O₂ tension from 21 per cent to 100per cent increased the oxygen uptake of dormant seeds more thanthat of non-dormant seeds (an increase of 53 per cent as against20–23 Per cent). In dormant seeds there was a concomitantincrease in CO₂ output (about 50 per cent), but the CO₂ outputof non-dormant seeds was hardly affected. High concentrations of CO₂ are inhibitory to the germinationof both dormant and non-dormant barley seeds. At a concentrationof 10 per cent, however, CO₂ is inhibitory only to dormant seeds,although at 2.5–5 per cent it is sometimes stimulatoryto the germination of dormant seeds. A 24–h treatmentwith appropriate concentrations of ethanol, lactic acid, oracetaldehyde is also stimulatory to the germination of dormantbarley seeds. Histochemical investigations in barley indicated the presenceof peroxidase, cytochrome oxidase, and -glycero-phosphate dehydrogenasein the embryo, aleurone layer, and in a layer associated withthe testa. A number of other redox enzymes were detected inthe embryo and aleurone layer only. No differences in distributionor intensity of activity were detected between dormant and nondormantseeds.     

Stomatal Responses of Phaseolus vulgaris L. Seedlings to Potassium Chloride in the Nutrient Solution

Alteration in KNO₃ and KCl levels of culture solutions resultedin the production of a series of Phaseolus vulgaris seedlingscontaining a range of chloride levels in the primary leaves;such treatments did not affect leaf potassium content. Irrespectiveof the leaf chloride content the stomata responded to increasedlight intensity by a decrease in stomatal resistance. The stomataof seedlings grown in culture solutions containing KCI offeredhigher diffusive resistances than those of seedlings not receivingthis treatment. This increase in stomatal resistance was foundover the whole range of elevated leaf chloride contents produced.Presence of chloride in the leaf tissue did not, however, affectstomatal responses to fluctuations in atmospheric CO₂ concentration.