Microcuttings of seven genotypes of almond (Prunus dulcis Mill) used as peach rootstocks, showed different rooting ability in vitro. No direct relationship was found between peroxidase activity and total phenol content, determined in the whole microcuttings prior to the root inducing treatment, and the rooting ability of these genotypes. However, a positive relationship was found between free indole-3-acetic acid (IAA) level and IAA-aspartate and the rooting response. After transferring into the rooting medium, peroxidase activity of the easiest-to-root genotype increase up to a peak and then declined and the total phenol content showed an opposite trend. These variations did not occur in the most difficult-to-root genotype.

Hydrolysis of acetylthiocholine and butyrylthiocholine has been observed in aqueous extracts from petunia pollen and pistils. The reproductive organs of self-compatible clone showed a higher rate of choline ester hydrolysis than those of self-incompatible clone. The highest rate of acetylthiocholine hydrolysis blocked by the cholinesterase inhibitors (physostigmine and neostigmine) was characteristic for the pollen of self-compatible clone. The incomplete (25 - 40 %) inhibition of hydrolysis in pistil extracts of self-compatible clone suggests the presence of unspecific esterases. The eight-fold lower hydrolysis was observed in the pistils of self-incompatible clone as compared to the pistils of compatible clone; neostigmine completely blocked this low hydrolytic activity. The treatment of flower buds with physostigmine and neostigmine (10-5 - 10-3 M) decreased the seed production by 10 - 20 % in compatible clone. When the surfaces of pistil stigmae were treated with physostigmine and neostigmine (10-5 - 10-3 M) before pollination, the seed formation was inhibited by 95 % after both self- and cross-pollination.

Studies on meiotic behaviour and pollen fertility have been carried out in Zephyranthes candida, Z. grandiflora and Z. flava. Maximum meiotic abnormalities in chromosome behaviour were observed in Z. candida and Z. grandiflora. There were variations in the number of bivalent formation, multivalents and anaphasic separation. All types of abnormalities were found to be associated with low percentage of pollen fertility. In Z. flava, chromosomal aberrations were low and pollen fertility was high.

Gametophytes cultured in solutions containing 0.0 to 0.7 % NaCl exhibited no change in ultra structural organization of chloroplasts. In 1.0% NaCl-grown gametophytes, there were thinner granal stacks, relatively larger spaces between granal thylakoidal membranes and larger plastoglobuli in the chloroplasts. These changes were accompanied by a decrease in photosynthesis. Cup shape, horseshoe shape, ring shape, and amoeboid mitochondria were observed in gametophytes grown in 0.0 to 0.7% NaCl. Only round mitochondria were observed in the gametophytes grown in 1.0 % NaCl. Mitochondria seemed to be more resistant to salt stress compared to chloroplasts. There was no direct relationship between changes in respiration rate and changes in mitochondrial shape among gametophytes grown in different NaCl concentrations.

Fully expanded leaves of tomato (Lycopersicon esculentum) growing with either complete or nitrogen-deficient nutrient solution were analysed for leaf water status, gas exchange and chlorophyll fluorescence during the vegetative and reproductive phases. N-deficiency did not affect leaf water relations but did decrease light saturated photosynthetic rate as well as stomatal conductance in the vegetative stage. A lower variable to maximum fluorescence ratio (Fv/Fm) was found in N-limited plants which also showed an increase in leaf starch content and in starch to sucrose ratio. The inhibition of photosynthesis and the alteration of photosynthates partitioning were responsible for the growth reduction in N-stressed plants. During the reproductive phase the limitation of photosynthesis may be due to a large accumulation of starch which determines both a decrease in the carbon demand from the sinks and a decrease in CO2 conductance in the mesophyll.

Mutagenesis provoked by exposure to increased concentration of antibiotics of five indigenous Rhizobium galegae strains resulted in the generation of several antibiotic-resistant mutants. The mutants differed from the wild type and one from another in respect to the nodulation capacity, the nitrogenase activity, the nodule ultrastructure, and the plant growth response. Galega plants inoculated with mutants resistant to streptomycin and rifampicin formed nodules with higher nitrogenase activity and accumulated more shoot dry biomass than plants inoculated with the parent strains. Resistance to kanamycin and nalidixic acid was associated with significant decrease of nitrogenase activity. A correlation between nitrogen-fixing efficiency and nodule infected cell ultrastructure was found. When the bacteroids occupied about 10 times higher area in infected cells of nodule than peribacteroid spaces and host cytosol had electron dense and homogenous structure, the nitrogenase activity was the highest.

A reliable protocol for the regeneration of onion through repetitive somatic embryogenesis was established. Embryogenic callus was derived from mature seeds on Murashige and Skoog (MS) medium supplemented with 2 mg dm-3 2,4-dichlorophenoxyacetic acid (2,4-D). Somatic embryos aroused on the surface of calli cultures and formed plantlets after the removal of 2,4-D or its substitution with 1 mg dm-3 kinetin (Kin). Reculturing the somatic embryos on 2,4-D containing medium led to secondary embryos formation. The embryogenic cultures which were preserved for five months on maintenance medium containing 2 mg dm-3 2,4-D + 0.5 mg dm-3 Kin have retained their ability for regeneration, while those kept on 2,4-D only, failed to form plantlets. Electrophoretic analysis of total soluble proteins revealed that the competence for successful conversion of somatic embryos into plantlets is associated with the expression of new set of proteins (112, 58 and 30 kD). The regenerated plants were successfully transferred to the soil.

Pre-submergence reserve saccharides was found adequate to substantiate the survival of tolerant cultivar under flooding. Survival percentage declined in both tolerant and susceptible cultivars with less saccharide content. However, it was more apparent in susceptible cultivar. Plant height, fresh and dry mass of shoots, leaf mass/area ratio and starch content per plant before flooding showed significant positive association with submergence tolerance. Hence, the improved seedling vigour could be used to increase submergence tolerance.

The effects of kinetin (Kn) on pigment content and electron transport activities (ETA) in wheat leavesin vivo and chloroplastsin vitro aging in light was investigated. Excised wheat leaves were infiltrated with Kn for 3 h under irradiation. The treatment increased zeaxanthin (Zx) content by 40% and also increased chlorophyll (Chia, Chib) and major carotenoid (Car) contents in the leaves (per fresh mass unit). Chloroplasts isolated from Kn treated leaves, when incubated in light for 4 h showed relatively lower pigment loss and slower loss of ETA compared to the chloroplasts of untreated leaves. These observations suggest photoprotective action of Kn. The photoprotection was more prominent when Kn was applied directly to the irradiated chloroplastsin vitro. Moreover, chloroplasts agingin vitro under irradiation without Kn treatment lost pigments and ETA. Within 3 h of irradiation, both whole chain (H₂O to methylviologen) electron transport as well as photosystem (PS) 2 activity were completely lost. However, in the chloroplasts treated with Kn, the loss of pigments was slow and even after 4 h of irradiation the chloroplasts retained 15 % of PS 2 and 9 % of whole chain ETA. In the untreated chloroplasts, the loss of Zx after 4 h of irradiation was 49 % whereas in Kn treated samples its level was 1.3 times higher than that of control. Since a higher level of Zx was maintained in Kn treated chloroplasts, photoprotective action of Kn is possibly mediated through Zx.

A method for micropropagation ofDalbergia sissoo has been developed. Single node segments obtained from coppice shoots of a mature tree (20 - 25 year old) produced 3-4 shoots per explant on Murashige and Skoog (MS) medium containing 4.4 x 10^-6 M benzylaminopurine (BAP) and 4.4 × 10^-7 M of Β-naphthoxy acetic acid (NOA) (shoot multiplication medium) within 4 weeks. Thein vitro regenerated shoots were 3 - 4 cm in length and provided 2 to 3 culturable nodal segments which on shoot multiplication medium again produced 3-4 shoots. Following this procedure 18-24 shoots were produced from single nodal segment within 60 d. 80 % of the shoots directly produced five roots when they were firstly treated with MS medium supplemented with 10^-5 M indole-3-butyric acid (IBA) and subsequently transferred to half strength liquid MS medium containing 1 % activated charcoal followed by half strength liquid MS free hormones, vitamins and activated charcoal. Thein vitro raised plants were hardened for survival after transplantation to soil by exposing them to various humidity conditions, gradually from higher to low, with nearly 100 % transplant success.

Sugar beet grown in pots was sprayed with N⁶-(m-hydroxybenzyl)adenosine, (mOH)- [9R]BAP, one of the synthetic cytokinins. Root tissue was then examined for respiration and for H⁺-adenosinetriphosphatase activity and both leaf and root tissue served as the object for 6-deoxy-D-glucose and 2-aminoisobutyric acid uptake estimations. Treatment with (mOH)[9R]BAP depressed the uptake of oxygen by the roots of both young and old plants by 17 - 30 % while addition of (mOH)[9R]BAP to the respiring slices decreased it by 10 - 23 %. Uptake of 6-deoxy-D-glucose was mostly diminished byin vivo spraying with the cytokinin (by up to 12 % in leaves and by up to 60 % in roots), as well as by adding it to the experimental vessel (insignificantly in the leaves but by up to 80 % in the roots). The H⁺-ATPase activity was stimulated bothin vivo andin vitro appreciably in young plants but not at all in plants at the end of their vegetation period.

Mungbean (Vigna radiata L. Wilczek cv. Sujata and cv. K851) seedlings were grown in paper towelins in dark under 0, 0.5, 1, 2 and 3 % (m/v) NaCl salinity. Germination percentage, shoot and root length, fresh mass of both cultivars decreased with salinity. Total soluble saccharides and proline accumulated in the root and shoot of salt stressed seedlings. The proline accumulation in the root was four to five times higher than that of the shoot of NaCl treated etiolated mungbean seedlings.

Indole-3-butyric acid (IBA), phenylacetic acid (PAA) and naphthaleneacetic acid (NAA) were applied at a concentration of 10^-4 mol dm^-3 to stem cutting bases ofPopulus x canadensis Moench. During adventitious root formation, the content of indole-3-acetic acid (IAA) in cutting bases was estimated using the fluorimetric method. In the control variant, a rapid increase in endogenous IAA appeared after 24-h cultivation followed by gradual decrease during the following days. In contrast, the variants treated with IBA, PAA, and especially NAA exhibited firstly a decrease in endogenous IAA content and only afterwards an increase, reaching a maximum 48 h after excision. As root regeneration proceeded gradually, a decrease in the level of endogenous IAA occurred in all treatments. The first adventitious roots appeared in all treatments after 216-h cultivation.

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.