The effect of the proteins extracted with 1 M LiCl from theCicer arietinum etiolated epicotyl cell walls on the degradation of polysaccharides extracted with alkali was studied. The hemicellulosic polysaccharides were fractionated into three fractions extracted with 4 % KOH, 4 % KOH containing 8 M urea, and 24 % KOH. The protein extract showed exo-glycanase activity against all three hemicellulosic fractions whilst endo-glycanase activity was shown mainly against the hemicellulosic polysaccharides extracted with 4% KOH.

The net photosynthetic rate (P_N), stomatal conductance (g_s) and transpiration (E) ofHardwickia binata Roxb. leaves were reduced due to decrease in the leaf water potential (ψ_w) from -2.0 to - 5.7 MPa. P_N partially recovered in the treated plants upon rewatering. Decrease in g_s due to water stress may be the main factor for reduction of P_N.

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.

Plant tissue cultures established from isolated embryos or cotyledons were used to investigate the lectin biosynthesis inCanavalia virosa. The lectin (CVL) was detected by double immunodiffusion and hemagglutination tests. CVL was present in all callus cultures. The stem and leaf of the plantlet generated from the embryo also contain CVL, but no CVL was detected in the roots. As compared to mature seeds, callus derived from cotyledon of immature seeds exhibited the largest CVL content.

The responses of barley and wheat seedlings to lead and cadmium ions in relation to the concentration and duration of treatment were studied. Both metals inhibited seed germination and growth of roots and shoots, but the toxic effect of cadmium was observed at lower concentrations. Inhibition of seedling growth was already recorded already within a day after the beginning of the treatment, and then increased further. The sensitivity of the processes studied to both the metals decreased in the order: root growth, shoot growth and seed germination. The resistance of barley and wheat to lead was similar, whereas the resistance to cadmium was higher in barley

Foliar sprays with N ⁶-(m-hydroxybenzytyadenosine, (mOH)-[9R]BAP, one of the synthetic cytokinins, were applied to field-grown sugar beet twice during the vegetation period: before full canopy closing (I), 6 weeks before harvest (II) or both. Application of (mOH)[9R]BAP retained high cytokinin content that usually declines prior to harvest. The total content of isoprenoid cytokinins at harvest was 2.6-fold higher in (mOH)[9R]BAP-treated plants as compared to the controls. Treatment I had no significant effect on contents of chlorophylls (Chl)a andb and carotenoids, nor on the rates of net photosynthesis (P_N) or photorespiration (R_l), or on CO₂ compensation concentration (Γ) measured during the whole vegetation period on detached leaves under optimum environmental conditions. Increased values in P_N, R_L and Chla andb contents were found in variantsII and I+II linked with a delay in leaf senescence before harvest. Transpiration rate and stomatal conductances of adaxial and abaxial epidermes were not significantly affected by any treatment.

In mustard(Brassica juncea L.) addition of 20 mM nitrogen (in the form of NaNO₃) inhibited after 50 d the activities of carbonic anhydrase and nitrate reductase and net photosynthetic rate. However, when nitrogen was applied in association with the foliar spray of gibberellic acid, the inhibition was reversed and the above parameters and also leaf area index and dry mass were enhanced.

Leaves of micropropagated highbush blueberry (Vaccinium corymbosum) cv. 'Bluetta' have been observed during the acclimatization phase. In vitro-developed leaf cells were circular and small, the spongy parenchyma was discontinuous and disorganized and formed by 1-2 layers of cells with large intercellular spaces and the palisade to spongy mesophyll thickness ratio was 1:1.5. After rooting ex vitro, the first leaves formed under natural conditions showed substantial changes in the anatomical characteristics. After 6 months, the plants produced leaves similar to those in field-grown plants. The palisade cells were rectangular, the spongy parenchyma was formed by 3-4 layers of cells and the intercellulars were around the stomata. Leaves from field-grown plants lost 24 % of water during 150 min after excision while leaves from in vitro shoots lost about 50 % of water in the same time. Leaves from in vitro shoots showed a higher number of smaller stomata (361 per mm²), with the guard cells forming a circular ring; the stomata frequency in field-grown leaves was 241 per mm² and the guard-cells were elliptical.

Investigations were carried out to determine the sites of lead uptake within the frond and the root ofLemna minor. With the sodium rhodizonate four regions favoured in lead uptake were distinguished: the frond region between the base and the node, the basal part of the root, and the regions at the proximal and distal ends of the root cap. For analysis in electron microscope only the root regions were chosen. The highest rate of lead uptake was found in the basal part of the root. Lead was present in the apoplast of this region after 5 min of exposure and was observed in the stelar cells after 30 min of incubation. Lead deposits were detected mostly in the cell walls adjacent to the plasma membrane and in the lumen of several endomembrane compartments - the endoplasmic reticulum (ER), dictyosomal vesicles, nuclear envelope and the vacuoles. Lead induced changes of cell ultrastructure; an increase in the number of membraneous structures, swelling of ER cisternae and distortion of the dictyosomal cisternae were observed after 2 to 6 h of exposure.

Changes in growth characteristics and photochemical activities inVigna unguiculata L. Walp seedlings maintained at constant temperature of 10, 20, 30 and 40 ‡C under control and ultraviolet-B enhanced radiation (UV-B) were investigated. UV-B retarded the shoot elongation and also leaf expansion to a great extent at 30 ‡C but produced only marginal changes at 20 and 40 ‡C. Similar response was also observed with respect to changes in leaf fresh and dry masses and total chlorophyll (Chl) content under these temperatures. At 10 ‡C the total Chl content was 3-fold higher under the treatment than under control conditions. In seedlings growing at 20 and 30 ‡C the overall photosynthetic electron transport (H₂O -> methyl viologen) showed a significant enhancement during the 36-h UV-B treatment and thereafter a gradual reduction. Although a similar trend was found in photosystem 1 (PS1), the inhibition even after 60 h of UV-B treatment was not statistically significant. Photosystem 2 (PS2) activity was inhibited in seedlings treated for 60 h by UV-B at 20 and 30 ‡C. However, no inhibition was observed at 40 ‡C. No detectable photochemical activity was found in seedlings grown at 10 ‡C under either control or UV-B enhanced irradiation although the chloroplasts contained Chl.

Leaf bearing stems ofCuratella americana L. were very susceptible to induced cavitation: embolisms began at a pressure of 0.5 MPa (15 %) and at 2.0 MPa most of the conductivity was lost (85 %). Nevertheless, in nature similar leaf specific conductivities, of about 90 x 10^-5 kg m^-2 s^-1 MPa^-1 during both wet and dry seasons indicated absence of drought induced embolisms. Leaf water potentials were neither very negative or considerably different between seasons but stomatal conductance decreased from 236 mmol m^-2 s^-1 measured during wet period to 100 mmol m^-2 s^-1 during drought season. Therefore, it was concluded thatCuratella had an accurate homeostatic balance of leaf water status to keep up xylem integrity.

The content of abscisic acid (ABA) in abaxial leaf epidermis of the host (Capsella bursa pastoris) and the unattached hemiparasiteMelampyrum arvense showed diurnal changes. ABA content increased during the light period and declined rapidly upon the darkening of leaves. In an attached hemiparasite the content of ABA in the epidermis was maintained at an almost constant level irrespective of the diurnal cycle. As compared with the maximum level in the host, at the end of the light phase the content of ABA in abaxial epidermis constituted about 70 % and 164 % in the unattached and attached hemiparasite, respectively. No significant changes in ABA content were recorded in adaxial epidermis. In all the samples abaxial/adaxial epidermis ABA content ratio was about 3.6:1 in light phase. In darkness this ratio decreased to about 1.1:1 in the host and the unattached hemiparasite and did not show significant change after attachment. ABA content ratio in mesophyll was 1:0.7:1.5 for the host, the unattached, and attached hemiparasite, respectively. In comparison with the host the concentration of ABA in xylem sap of the hemiparasite constituted about 31 % and 152 % for the unattached and attachedM. arvense, respectively.

The distribution of the stress-related anionic peroxidase (srPRX) activity was investigated in various organs of cucumber (Cucumis sativus L. cv. Laura) during their development by activity staining and immunoblotting. In shoots, including cotyledon, leaf, stem and tendril, three stress-related peroxidase isoenzymes were present, particularly in old ones. The PRX1 was the only srPRX isoenzyme found in both young and old roots. As fruits became mature, srPRX activity increased dramatically and was particularly enriched in the external parts of the fruit. The PRX1 isoenzyme was highly accumulated in the course of seed germination, while the absence of other two srPRX isoenzymes (PRX2 and PRX3) was recorded. The possible function of the srPRX is discussed, with respect to this spatio-temporal distribution.

Cadmium, copper and zinc ions at high concentrations partially released scarified freshly-harvested seeds ofStylosanthes humilis from physiological dormancy. This response to toxic metals increased along with seed postharvest ageing. Cobalt and silver ions, and abscisic acid impaired metal-promoted germination.

Paclobutrazol (PB), a triazole growth retardant and an inhibitor of gibberellin biosynthesis, reduced at 17 μM concentration the adventitious root formation of bean primary leaf cuttings. Treatments with 5 μM ABA or 4 μM Ethrel, an ethylenereleasing compound, restored the rooting of PB-treated cuttings. Ethylene production and the content of the precursor 1-aminocyclopropane-l-carboxylic acid (ACC) were enhanced in root-forming tissues of PB-treated petioles 48 h after ABA application. The effect of ABA could be abolished by 10 μM CoCl₂, an inhibitor of ACC oxidase. Thus, ABA might stimulate rooting through its effect on ethylene release. 2 mM silver thiosulphate, an inhibitor of ethylene action, decreased the rooting of PB-treated cuttings similarly to Co²⁺, but failed to negate the ABA effect. These data indicate that the effect of PB on rhizogenesis is not associated directly with the inhibition of the biosynthesis of gibberellins

Supply of 0.01 to 1.0 mM lead acetate to greening pea(Pisum sativum L.) leaf segments either in the absence or in the presence of inorganic nitrogen lowered total chlorophyll (Chl) content. During a time course study, there was not any appreciable effect of Pb²⁺ upto 4 h but thereafter Pb inhibited Chl synthesis. While supply of succinate, cysteine dithiothreitol, 5,5-dithio-bis-2-nitrobenzoic acid and NH₄C1 had no protective action against Pb²⁺ toxicity, and glycine, glutamate 2-oxoglutarate, MgCl₂, KH₂PO₄, CaCl₂, KC1 protected only partially, reduced glutathione (GSH) could completely overcome the inhibition of Chl biosynthesis by the metal. It is suggested that Pb²⁺ interferes with Chl biosynthesis through GSH availability

Growth, nodulation and N₂ fixation inGlycine max L. Merr., cv. Biison as affected by the relative humidity of air (RH) during the dark period (95 or 50 - 65 %) and day/night root temperature (T_r) (28/28, 25/25, 18/18, 22/28, 22/18 °C) were studied. The growth parameters (plant fresh and dry mass, yield), nodulation (nodule number and fresh mass) and N₂ fixation abilities (total nitrogen content, nitrogenase activity) increased significantly with the increasing T_r. In addition, at the same T_r during the day all studied parameters were increased at the higher T_r during the dark period. Growth, nodulation and N₂ fixation were significantly enhanced at low RH. The findings indicate that all studied parameters could be regulated by environmental factors during the dark period.

Binding protein for N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, was studied by analysis of the effects of reactions which modify particular amino acid side chains upon their binding activity. Na₂SO₃, N-ethylmaleimide (NEM) and dithiobisnitrobenzoic acid all inhibited the specific binding of NPA to its binding protein fromAcer pseudoplatanus L. cells. The presence of 10^-6 M Na₂SO₃ in the binding assay reduced the affinity of the binding protein to NPA from K_d of 1.5 £ 10^-8 M to K_d of 2.1 £ 10_-8 M, while concentration of the binding protein was not significantly changed. When the same analysis was applied to NPA binding to the NEM-treated membrane particles, it was found that NEM inactivated binding without changing the affinity for NPA. This study revealed the importance of sulphydryl group(s) in the maintenance of NPA binding protein activity.

The plants of mustard (Brassica juncea L.) were treated with 0, 25 and 50 ΜM gibberellic acid (GA₃) at three fully developed leaf stage (30 d after sowing). Effect of GA₃ on carbonic anhydrase activity, photosynthetic rate, leaf area index and dry mass was studied at 50, 70 and 90 d after sowing. At harvest 1000 seed mass, pod number and seed yield were recorded. GA₃ treatment (50 ΜM) enhanced all the characteristics studied.

The detrimental effect of NaCl was found at the oxidation site of photosystem 2 (PS2). An impairment of PS2 was caused by damage of the oxygen evolving polypeptides (33, 23 and 20 kDa) of thylakoid membranes as well as by changes in the unsaturated and saturated fatty acids. Application of triacontanol, TRIA (1 mg kg^-1) ameliorated the effect of NaCl and promoted the ratio of unsaturated to saturated fatty acids, the rate of¹4CO₂ fixation and the activity of ribulose 1,5-bis-phosphate carboxylase.

Echinochloa colona regeneration via organogenesis in callus cultures derived from leaf base and mesocotyl expiants andin vitro flowering were achived. Shoot bud regeneration was achieved on Murashige and Skoog's (MS) basal medium supplemented with 6.66 μM 6-benzylaminopurine (BAP), 2.68 μM 1-naphthalene acetic acid (NAA) and 3 % (m/v) saccharose. Regenerated shoots were rooted on half strength basal MS medium with 2 % (m/v) saccharose devoid of growth regulators. About 90 -95 % of rooted plantlets survived in the greenhouse.In vitro flowering was induced in the regenerated shoots derived from callus on half strength MS medium supplemented with 4.4 μM BAP, 74.07 μM adeninesulphate, 0.72 μM gibberellic acid, and 3 % (m/v) saccharose. The frequency ofin vitro flowering was 80 - 90 % in three repeated experiments. Fertile seeds were recovered fromin vitro grown plantlets which were subsequently germinated into plants.

Pathogenesis-related (PR) proteins from pepper (Capsicum annuum L.) cv. Americano (tolerant) and cv. Smith-5 (sensitive), both elicited by infection with cucumber mosaic virus (CMV), were assayed for chitinase and glucanase activities. Two basic PR-proteins, M_r 49.0 and 28.0 kD, were elicicited from the intracellular fraction (INTRA-F) of both cvs. by CMV infection, while four acidic M_r 15, 19, 36 and 40 kD and two basic M_r 21.2 and 24 kD PR-proteins were elicited from the intercellular fluid (IF) of cv. Americano leaves. Five acidic M_r 21.5, 23.2, 24.4, 25.2 and 36 kD and five basic M_r 23.3, 26, 28.8, 30 and 32.3 kD PR proteins were elicited from the IF of cv. Smith-5. Isoelectric focusing (IEF) of the IF and the INTRA-F proteins revealed the occurrence, in both pepper cultivars, of one acidic M_r 36 kD and one basic M_r 25 kD PR-protein with glucanase activity. After native-PAGE for acidic proteins, the acidic PR-protein of Rf 0.7 and M_r 36 kD present in the IF of both pepper cvs. showed glucanase activity. Native-PAGE for basic proteins of the INTRA-F showed the presence of one band (Rf 0.61, M_r 25 kD) common to both cvs. and two additional bands (Rf 0.49, M_r 26 kD and Rf 0.79, M_r 33 kD) in the cv. Americano with glucanase activity. The specificity shown by the basic PR-proteins suggests glucanase activity is involved in the mechanisms of resistance to CMV in the cv. Americano. There was no difference in chitinase isoform patterns between the two pepper cultivars analyzed. After IEF of the IF proteins, one acidic chitinase isoform was detected. Native-PAGE separation of the IF showed one band (M_r 30 kD) with chitinase activity. Chitinase activity was not detected in the INTRA-F of either cultivar.

Leaf gas exchange, plant growth and leaf ion content were measured in wheat (Triticum durum L. cv. HD 4502) exposed to steady- state salinities (1.6, 12.0 and 16.0 dS nr^-1) for 8 weeks. Salinity reduced leaf area and number of tillers, and increased Na⁺ and Cl^- concentrations in leaves. Leaf- to- leaf gradients of these ions were observed. The oldest leaf contained 6 to 8 times more Na⁺ and Cl^- than the flag leaf. Net photosynthetic rate (P_N), transpiration rate (E) and stomatal conductance (g_S) were the highest in flag leaf, declined in the middle and fully expanded leaves, and were minimum in the oldest leaves. These processes were reduced by salinity with similar leaf- to- leaf gradients. Intercellular CO₂ concentrations in the older leaves were higher than in the flag leaf in non-saline plants, and increased similarly with salinity. Leaf age was the major factor in reducing P_N, and senescence processes were promoted by salinity.

The changes in ubiquitin mRNA level in intact plants of both susceptible (cv. Spunta) and partially resistant (cv. Pampeana-INTA) potato cultivars after inoculation with low doses (l0³ sporangia cm^-3) ofPhytophthora infestons were studied after 72 h of treatment. Inoculation leads to 5-fold accumulation of potato ubiquitin transcripts in both cultivars. This result supports the connection between ubiquitin expression and defense reaction in plants.