Catalase is an enzyme unique to glyoxysomes in developing poppy seedlings. Catalase activity is very low in endosperm and in embryo of germinating poppy seeds. During postgerminative growth and development the enzyme activity increases rapidly with maximum in endosperm on day 2 and in developing seedling on day 3. A rapid decline of enzyme activity parallells the extension growth of poppy seedlings. Three electrophoretic forms of catalase have been detected in isolated glyoxysomes and partially purified catalase preparation. Electron microscopic observation indicates the presence of catalase in glyoxysomes of parenchyma cells of poppy seedling cotyledons. Numerous lipid bodies and electron-dense deposits in vacuoles are the most characteristic feature of these cells.

Single treatment of expanding radish leaves with N₁-(2-chloro-4-pyridyl)-N₂-phenylurea (4-PU-30) lead to the stimulation of root cambial tissue activity and root growth. Leaf thickness, the volume of chlorophyll (Chl) containing cells per unit leaf area, starch content in the chloroplasts, and the Chl content increased simultaneously. These alterations were associated with increased leaf net photosynthetic rate and stomatal conductance in treated plants.

Dry mater, water content, water, osmotic and pressure potentials, content of saccharides and potassium were measured duringin vitro cultivation ofVitis rootstocks. Three cases were compared: a) the micro-cuttings with normal growth; b) micro-cuttings which stop their growth after 15 d of culture, and c) micro-cuttings reactivated by 6 d of continuous darkness.
Major differences were observed in water content and osmotic potential. The stopping of growth was not a specific property of buds, but was probably due to restriction of translocation of saccharides and water in the shoot.

The effects of fusaric acid, a phytotoxin produced byFusarium pathogens, on the metabolism of isolated maize root mitochondria and on maize seed germination and seedling growth were investigated. The phytotoxin inhibited basal and coupled respiration when succinate and α-ketoglutarate were the substrates. Coupled respiration dependent on NADH was inhibited, but basal respiration was not. Consistently, succinate cytochromec oxidoreductase activity was decreased whereas NADH cytochromec oxidoreductase was not affected. The ATPase activities of carbonyl cyanide p-trifluoro-methoxyphenyl hydrazone stimulated mitochondria and of freeze-thawing disrupted mitochondria were inhibited. These results indicate that the phytotoxin impairs the respiratory activity of maize mitochondria by at least three mechanisms: (1) it inhibits the flow of electrons between succinate dehydrogenase and coenzyme Q, (2) it inhibits ATPase/ATP-synthase activity and (3) it possibly inhibits α-ketoglutarate dehydrogenase. Seed germination and seedling growth were also affected by fusaric acid with the most pronounced effect on root development. These effects can possibly contribute to the diseases ofFusarium- infected plants

Spring barley seedling were grown in the dark for 21 d and respiration rates of the whole plant (including the seed), of the shoots, and of the roots were determined. A function describing the growth and maintenance components of respiration was interpolated through the experimental points and its parameters in plants under different mineral nutrition were compared. The plants grown in a complete nutrient solution showed the highest growth rate in the initial phase of development and thus reached the maximum respiration rate earlier than plants in the other variants. The highest proportion of substrate was respired in the shoot. Plants grown under deficiency of phosphorus and magnesium had a slower respiration rate than plants grown in the complete nutrient solution (NP), whereas the amount of respired substrate in plant parts was similar to that recorded in the NP plants. Plants grown in distilled water showed the lowest growth efficiency and respirated the highest proportion of substrate in the root.

Plants of two wheat (Triticum aestivum L.) cultivars differing in salt tolerance were grown in sand with nutrient solutions. 35-d-old plants were subjected to 5 levels of salinity created by adding NaCl, CaCl₂ and Na₂SO₄. Growth reduction caused by salinity was accompanied by increased Na⁺ and Cl^- concentrations, Na⁺/K⁺ ratio, and decreased concentration of K⁺. The salt tolerant cv. Kharchia 65 showed better ionic regulation. Salinity up to 15.7 dS m^-1 induced increased uptake of Na⁺ and Cl^- but higher levels of salinity were not accompanied by further increase in uptake of these ions. Observed increases in Na⁺ and Cl^- concentrations at higher salinities seemed to be the consequence of reduction in growth. Uptake of K⁺ was decreased; more in salt sensitive cultivar. This was also accompanied by differences in its distribution.

The content of lead in greening etiolated barley leaves remained the same, regardless the time of incubation of excised leaves in the presence of lead ions (8-24 h). The lead deposits have not been detected within mesophyll cells, but were found in intercellular spaces of mesophyll, in guard cells and in cuticle covering stomata. This suggests that lead may be transported in the leavesvia transpiration stream. Lead reduced the content of chlorophyll, especially chlorophyllb content and the average number of grana, whereas in the presence of kinetin the content of chlorophyll increased. In the combined treatment (lead + kinetin) kinetin diminished the inhibitory effect of lead on the chlorophyll content. The number of chloroplasts in mesophyll cells remained unchanged after lead treatment, whereas kinetin alone or applied together with lead increased the average chloroplasts number. The thylakoids system in chloroplasts of kinetin and kinetin + lead treated plants was similar to that observed in control, although the grana number was smaller. Both lead and kinetin increased the content of condensed chromatin in nuclei.

In date palm (Phoenix dactylifera L.) leaves, the main compounds of the phenolic pool were quercetin and isorhamnetin heterosides, (+)-catechin and (-)-epicatechin. Although previously observed only in date palm fruits, 5-caffeoylshikimic acid (dactylifric acid) and its positional isomers (3-caffeoylshikimic acid and 4-caffeoylshikimic acid) were detected also in the leaves and roots. Quantitative, but not qualitative, differences between cultivars resistant and susceptible toFusarium oxysporum f. sp.albedinis during growth period were observed

Decrease in leaf irradiance to 50 % due to shading of plants in glasshouse only during clear summer days did not induce significant changes in growth parameters, characteristics of water relations and epidermal conductance of two cyclamen cultivars. Thus the possibility of acclimation of plants to non-stable changes in environmental conditions was not proved.

The effect of NaCI stress on the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH) and glutamate synthase (GOGAT) in callus lines ofVigna radiata which differ in salt resistance, was studied at weekly intervals upto 28 d of growth. After 28 d, the NaCI resistant callus (selected at 300 mM NaCI) at NaCI concentrations higher than 200 mM maintained higher NR activity than non-selected line. NaCI stress also affects aminating and deaminating activities of GDH. The NADH-GDH activity in the presence of NaCI was higher in the resistant than non-selected line. On the other hand, NAD-GDH activity in both the lines was completely inhibited after 7 d of growth. The increased activity of NADH-GDH in resistant calli may play a vital role in protecting the cells from toxic effect of increased endogenous level of ammonia which probably accumulates due to efficient NO₃ ^- reduction. NADH-GOGAT activity was found to decrease under salt stress in both the callus lines. Nitrogen assimilation in salt-resistant calli under salt stress was found to be characterized by high NR and NADH-GDH activities, concomitantly with low GOGAT activity.

For clonal propagation ofAsparagus cooperi, shoot tips and node explants of 7, 20 and 35 d old spear from the region within 10 cm and below 25 cm from the apex were cultured in modified Murashige and Skoog's (1962) medium containing 6-benzylaminopurine (BAP). The required concentration of BAP varied in explants of different ages and types. In shoot tip culture, the rate of shoot multiplication was higher after 40 d than 60 d of culture. The maximum mumber (62-65) of shoots were obtained from shoot tip explants of 20 d old spear in the medium containing 2.0 mg dm^-3 of BAP, 80 mg dm^-3 of adenine and 0.02 mg dm^-3 of α-naphthalene acetic acid after 60 d of culture. From node cultures, high number of shoots were obtained after 30 d. Pretreatment with BAP in liquid medium for 48 h was effective for semirejuvenescence. The individual shoots produced roots in presence of indole-3-butyric acid and also in potassium salt of indole-3-butyric acid, the later being more effective. All regeneratns were cytologically stable.

The responses of seedlings of three fast growing tree species,Eucalyptus hybrid(E. camaldulensis × E. teriticornis), Casuarina equisetifolia andMelia azedarach, to different levels of soil moisture in controlled glasshouse conditions were compared. The survival percentage, height of plants, number of leaves per plant, number of branches, fresh mass and dry mass of roots, stems, branches and leaves decreased in the three species with increasing water stress. Stomatal frequency and length of stomata inEucalyptus andMelia also decreased with increasing water stress. However, no significant difference was obtained in the width of stomata and the ratio of number of open stomata to total number of stomata per unit area. The leaf thickness decreased, but the thickness of palisade parenchyma increased with increasing water stress inEucalyptus hybrid andCasuarina. Leaf thickness ofMelia did not show any significant variation due to water stress.

Glutamate dehydrogenase (GDH E.C. 1.4.1.2.4), glutamine synthetase (GS E.C. 6.3.1.2) and glutamate synthase (glutamine oxoglutarate amino transferase, GOGAT E.C. 2.6.1.53) activities, protein and organic nitrogen contents and growth of roots and shoots of maize seedlings raised in dark at 25±2°C in half strength Hoagland's solution containing different ammonium salts as source of nitrogen, were determined to assess the contribution of alternate pathways in ammonium assimilation. Ammonium nitrate or in some cases ammonium chloride appeared to be the best source for both root and shoot growth and for increase in protein, total nitrogen and the enzymes of ammonium assimilation. In roots, NH₄-nitrogen appeared to be assimilated by both GDH as well as GS-GOGAT pathways specially in the dark grown seedlings, while in shoots it was primarily by GS-GOGAT pathway.

This study examined whether 'Risnod2' and 'Risnod27' non-nodulating mutants of pea (Pisum sativum L.) provided with increasing concentrations of nitrate could achieve a growth and nitrogen accumulation comparable to their parental N₂-fixing cv. Finale. In the cv. Finale, nodule number, nodule dry mass accumulation, total C₂H₂-reducing activity of nodulated roots (TAR) and estimated N₂ fixation were considerably inhibited at 5.0 and 10.0 mM root medium NO₃ ^- concentrations. In contrast a 0.63 mM level stimulated both the nodule dry mass and TAR. The cv. Finale N₂-fixing plants grown on 0 to 2.5 mM NO₃ ^- levels had higher shoot N concentrations than the Nod^- mutants, but within the 5.0 to 10.0 mM levels the Nod^- mutants approached or even overtopped the N concentration of the cv. Finale plants. Compared with a high positive correlation found in the Nod^- mutants, shoot N concentration in the cv. Finale was negatively correlated with the root medium NO₃ ^- concentration. The pattern of nitrogen content in shoot dry mass was very similar to that seen in the shoot dry mass accumulation. The Nod^- mutants grown on the 5.0 and/or 10.0 mM NO₃ ^- level had plant dry mass, shoot nitrogen concentration, shoot nitrogen content, and root/shoot dry mass ratio comparable with those of the nodulating cv. Finale grown on the same nitrate levels.

The growth of primordia of marginal buds (marginals) which differentiate on leaf margins is correlatively inhibited on intactBryophyllum crenatum plants. Following leaf isolation, the marginals are released from this correlative inhibition, which process is accompanied within 2 to 10 h after leaf isolation with a decrease in the content of endogenous IAA in the leaf blade. This decrease can be enhanced by transversal cutting of the leaf blade into three parts which also results in enhanced subsequent growth of the marginals. The growth which follows after the release of the marginals from correlative inhibition is accompanied in cut leaf blades with an increased content of endogenous IAA in the period from 12 h to 7 d after leaf isolation when compared with uncut leaf blades. The highest content of endogenous IAA was recorded in the middle section, and the lowest IAA content in the basal section of the leaf blade.

Proline content, ion accumulation, cell wall and soluble peroxidase activities were determined in control and salt-treated calli (150 nM NaCl) and whole plants (30 mM NaCl) of two rice cultivars (salt sensitive cv. IKP and salt tolerant cv. Aiwu). Under salinity, the highest accumulation of Na⁺, Cl^- and proline occurred in calli, roots and younger leaves of cv. IKP, coupled with the highest decrease in K⁺ content; accumulations of Na⁺ and Cl^- were restricted to older leaves in cv. Aiwu. Relative growth rates of calli and roots or shoots from both cultivars were not linked to peroxidase activities. High concentrations (1 M) of exogenously applied glycerol did not inhibitin vitro activities of soluble peroxidase extracted from control and salt-treated calli or plants. Conversely, 35-55% (in cv. IKP) or 60-80% (in cv. Aiwu) of soluble peroxidase activities were found in presence of isosmotic proline concentration. There were no differences between proline and glycerol effects onin vitro cell wall peroxidase activities.

For maximum avoidance of somaclonal variation risks, the commonly used medium for somatic embryogenesis inPhoenix dactylifera has been lowered in growth regulators and activated charcoal. When initially cultured on MS basal medium containing only 150 mg dm^-3 charcoal, 5 mg dm^-3 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg dm^-3 benzylaminopurine (BAP), 10 to 20% of shoot-tip explants developed into embryogenic calli. The embryogenic potential has been maintained for over 24 months with no decline. In addition, this medium has been found to be more efficient than conventionaly one containing 3 g dm^-3 charcoal, 100 mg dm^-3 2,4-D and 3 mg dm^-3 2-isopentyladenosine (2IP). Plantlet regeneration was achieved when somatic embryos were subcultured to medium with 0.1 mg dm^-3 2,4-D and 0.5 mg dm^-3 BAP or without growth regulators.

Growth rate of leaves of winter barley (Hordeum vulgare L. cv. Efra) plant in thermal time correlated with the final length of the corresponding leaf (r = 0.66). The sum of effective temperatures corresponding to the time of growth of a particular leaf linearly increased with leaf insertion (r = 0.82). Phyllochron value in plants grown in the field with either natural or controlled photoperiod was dependent on phyllochron order, especially up to the double ridge stage (r = 0.89 and r = 0.74, respectively). The mean value of phyllochrons in the field variants showed a very good agreement with the value calculated on the basis of the change in day length at the time of seedling emergence.

Lemon plants (Citrus limonum L. cv. Verna) were grown in the field under two different flood irrigation treatments. The dry treatment received four irrigations per year (March, July, September and November) and the wet treatment one monthly. The amounts of water applied per year for dry and wet treatments were 340.0 mm and 1020.0 mm, respectively. The effects of the two treatments on certain aspects of the plant water relations during the period between flowering and the end of rapid fruit growth (critical period) were studied. Soil matric potential (ψm) and leaf water potential (ψi) values in the dry treatment revealed development of water stress during the experimental period. The water supply in the wet treatment seems sufficient to achieve the crop water requirements. The g₁ values in July were higher in the wet than dry treatments. Pronounced oscillations in g₁ from sunrise to afternoon were found especially in the dry treatment.

Phaseolus aureus Roxb. was exposed to HgCl₂ and Cd(NO₃)₂ either at the germination stage in concentration 0.5, 5 and 25 μM for 48 and 96 h, or at the seedling stage (5^th day of germination) in concentration 0.5, 5 and 20 μM for 6, 24 and 48 h. The germination and the growth of roots (germination stage treatment) were less in Hg than in Cd treatment. The seedlings (seedling stage treatment) were, however, more susceptible to Cd than Hg. Both root and leaf tissues of the plant treated at the germination stage showed enhanced lipid peroxidation and activities of the antioxidative enzymes (catalase, guaiacol peroxidase and ascorbate peroxidase), except the catalase in leaf in 25 μM Cd treatment. At seedling stage the content of malondialdehyde increased significantly only in the leaf tissue, during 6 h exposure. The activities of all the enzymes exhibited an increasing trend in both the tissue of the seedlings, particularly the leaf, at least after 24 and 48 h, except the catalase whose activity declined in response to Cd. Active involvement of the guaiacol and ascorbate peroxidases, rather than catalase, in scavenging cellular H₂O₂ was indicated. It was concluded that the two metals had little primary damaging effect on membranes.

Cadmium (Cd) and kinetin (Kin) significantly affected the growth and contents of chlorophyll (Chl) and of soluble and reserve (hydrolysable) saccharides in sunflower plants. Cd-treated plants had lower contents of Chl and soluble saccharides and produced less dry matter than control (Cd-untreated) plants. Chla stability to heat (CSI) increased at all Cd concentrations. The same was true for Chlb stability (0-10 μM Cd). Spraying sunflower shoots with Kin solutions counteracted the deleterious effects of Cd. Kin application enhanced the Chla andb contents, Chla/b ratio, content of soluble saccharides and dry matter, and to less extent Chl stability. The relative role of Kin in affecting the parameters tested (as indicated by η² values) was predominant while that of Cd was subsidiary except for Chla stability. The role of Cd×Kin interaction was dominant for hydrolysable saccharides. Hence spraying shoots of plants grown under increasing Cd concentration with Kin can partially alleviate inhibitory effects of cadmium.

Germination and seedling growth of pea (Pisum sativum L. cv. Rachna) was studied in salts and PEG-6000 solution having osmotic potentials -0.1, -0.2, -0.3, -0.4 and -0.5 MPa. At equivalent level of stress, NaCl proved more harmful to germination, seedling growth, vigour index, as well as initial mobilizing efficiency of food material from seed to the growing seedling, while PEG-6000 was more harmful to imbibition rate and mobilization efficiency in further days.

A field experiment was carried out to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in 33 or 66 mM NaCl and indolyl-3-acetic acid (IAA at 50 g m^-3), gibberellic acid (GA₃ at 100 g m^-3) or kinetin (100 g m^-3) on some tolerance criteria in wheat flag leaf at different stages of development. At various stages of flag leaf development pretreatment with 33 or 66 mM NaCl decreased degree of succulence (particularly 66 mM), relative growth rate, net assimilation rate, relative water content, K⁺ content and K⁺/Na⁺ ratio and at the same time induced accumulation of abscisic acid and Na⁺. In the majority of cases grain pretreatment with GA₃ or kinetin and to a lesser extent with IAA alleviated either partially or completely the deleterious effect of salinity on the above mentioned parameters.

The effect of 80 mM NaCl on the structure and ultrastructure of root cells ofPhaseolus vulgaris plants has been investigated. Roots of plants treated with NaCl were shorter and had less secondary roots than control plants. In control plants, epidermal cells were isodiametric and uniformly placed forming a thin layer, whereas in stressed plants, the shape and disposition of epidermal cells was less regular. The cortical cells of control plant were round-shaped and distributed allowing large and well defined intercellular spaces, whereas stressed plants presented irregular cells, which were interdigitated, thus decreasing the volume of the intercellular spaces. Presence of 80 mM NaCl did not result in significant differences in the number, shape or distribution of the cell organelles. Membrane vesiculation was often observed in cells of NaCl treated plants. Addition of 80 mM NaCl to the growth medium considerably increased the leakage of solutes from intact plant roots back to the solution especially K⁺ and Ca²⁺.

Effects of iso-osmotic levels of salts (NaCl, CaCl₂, Na₂So₂) and PEG-6000 on saccharides, free proline and nitrogen contents were studied in cotyledons of pea. Saccharide (total, reducing andnon-reducing) and nitrogen contents decreased with increasing the salt and water stress as compared to control at all the stages of seedling growth. PEG-induced stress had more deleterious effect on total saccharide content and non-reducing saccharide (NRS) content, while salt stress was more harmful to reducing saccharide (RS) and nitrogen content. Free proline content of cotyledons increased with increasing the salt and especially PEG-induced stress at all the stages of seedling growth.

The effect of five 3-(2-alkoxyphenylcarbamoyloxy)chinuclidium chlorides (alkoxy = butoxy-octyloxy) on survival of a wild-type strain and repair-deficient strains ofChlamydomonas reinhardtii was studied. There was a direct relationship with increased toxic effects in the algal strains as a function of the elongation of the alkyl chain of the alkoxy substituents of the phenylcarbamate acid derivatives. Repairdeficient strains were more sensitive than the wild-type strain. The recombination-deficient strain uvs10 expressed the highest sensitivity to the test agents. This suggests that a gene responsible for recombination repair is involved in an important role in DNA repair of damages induced inC. reinhardtii by the phenylcarbamic esters.

Influence of inoculation with efficient rhizobia or nitrate fertilization in alleviating salinity (NaCl, CaCl₂ and Na₂SO₄) stress was investigated in sand culture experiments. Shoot dry mass declined beyond salinity level corresponding to electrical conductivity (EC) 5.6 dS m^-1 in control or in inoculated plants and after EC 7.4 dS m^-1 in nitrate fed ones. Root growth was more sensitive and decreased at EC 3.3 dS m^-1. Nitrate reductase activity in leaves reduced at EC 3.3 dS m^-1 but in inoculated and nitrate fed plants it reduced at EC 5.6 dS m^-1. Na⁺ accumulation increased at EC 5.6 and 7.4 dS m^-1 in roots and, shoots, respectively. In inoculated and nitrate fed plants Na⁺ content in roots increased at EC 7.4 dS m^-1. Content of Ca²⁺ increased slightly only in shoots and content of K⁺ was unaffected. Besides inoculation, application of small doses of nitrogen should prove beneficial for legume cultivation in saline soils.

Phenolic content and IAA-oxidase (IAA-o) activity have been assayed in cells and medium of tobacco crown gall suspension culture in several stages of culture cycle. The highest content of total phenolics in the cells were found prior to cell division and in the middle stage of intensive growth. The beginning of intensive growth is accompanied by temporary reduction in phenolic level in the cells as well as their intensive secretion to the medium. In the second part of the culture cycle, when the phenolic production was weaker, the majority of these compounds were maintained in the cells.
The highest activity of IAA-o in the cells was detected in the middle stage of intensive growth, simultaneously with high phenolic content; following it a considerable decrease of IAA-o activity is correlated with maximum of chlorogenic acid (ChA) content (at reduced amount of total phenolics). IAA-o activity increased again at the end of the stage of intensive growth when the level of phenolics was low including ChA. These data suggest that IAA-o in relation to phenolic level determines cell growth in the culture.
In the culture medium - fairly distinct negative correlation between IAA-o activity and phenolic content suggests that the latter participates in enzyme activity regulation. During intensive growth IAA-o activity is strongly inhibited.
The results prove that phenolic level. IAA-o activity and auxin level are closely correlated and may constitute essential elements of a mechanism of regulation crown gall cell growth in culture.