Chloris barbata Sw. andCyperus rotundus L. from a mercury contaminated site near a chloralkali plant were tested for relative tolerance to Hg by root-elongation method. The above two species from the Hg-contaminated site exhibited high tolerance to Hg compared to the same species from a non-contaminated site. Tolerance to Hg was higher inChloris barbata than inCyperus rotundus.

Addition of either abscisic acid (ABA) or kinetin at 10^-6 M to salinized media (20-120mM NaCl) induced remarkable effects on growth ofPhaseolus vulgaris plants. Whereas ABA inhibited the plant growth and the rate of transpiration, kinetin induced stimulation of both parameters. Moreover, ABA increased proline and phosphorus concentrations in the salinized plants whilst kinetin decreased them.
ABA induced stimulation of the transport of K, Ca and Cl from root to shoot, accumulation of K, Na and Cl in root cells and inhibits the transport of Na and accumulation of Ca. Kinetin appeared to inhibit the transport and accumulation of Na and Cl, transport of K, and stimulates the accumulation of K and Ca as well as the transport of Ca. The highest influence of both ABA and kinetin was mostly observed when these hormones were used in combination with the highest concentration of NaCl (120 mM) in the medium.

The germination percentage of chick-pea (Cicer arietinum) Seeds was greatly reduced by temperatures of 30°C and 35°C. This thermoinhibition was overcome by ethylene (ethrel). Both ABA and PEG diminished ethylene production and germination percentage in a parallel way. FC, MGBG and CHA stimulated both ethylene production and germination. AVG reduced ethylene production to some extent but did not inhibit germination. CoCl₂ and PG completely prevented both ethylene production and germination; this effect was reversed by ethylene but not by its immediate precursor ACC. NBE prevented both germination and ethylene production. Our results suggest that high ethylene production rates are not essential for germination of chick-pea seeds but that certain quantities of ethylene may be required.

The effect of four bacterial and six fungal species on nodulation and growth ofVicia faba cv. Giza 3 inoculated withRhizobium leguminosarum biovarviceae strain RCR 1001 were assessed in a pot experiment.Bacillus cereus, Pseudomonas fluorescens, Aspergillus niger andA. quadriliniatus either alive cells or sterile filtrate significantly promoted nodulation, growth and nitrogen accumulation. Heat-killed cells had no effect.

Growth analysis indicated that carbon gain in the alpine succulentSedum album tended to take place early during the growing season. Leaf water potential remained unchanged for a considerable length of time after the imposition of water stress in the field. Induction of crassulacean acid metabolism (CAM) by protracted water stress occurred before any signs of stress could be observed in the leaves, and appeared to be influenced by a complex interaction of environmental conditions including temperature and duration of sunshine. Increased levels of proline and betaine towards the end of the growing season appeared to reflect seasonal changes.

Meristems from 25-90-year-old oak (Quercus robur L. andQ. petraea Matt.) trees and seed embryos were pretreated with polyvinyl pyrrolidone, ascorbic acid, cysteine and citric acid solutions. Tissues were cultured mostly on a WPM medium supplemented with different combinations and concentrations of growth regulators. All the different pretreatments showed a positive effect against the otherwise very rapid and harmful browning of the explants but ascorbic acid (100 mg dm^-3) proved to be the most effective. Shooting was induced from seed embryos and meristems originating from adult trees. Rooted plantlets were obtained from explants of seed embryos.

Stem internodes with axillary buds were excised from 5-year old trees ofFicus benjamina cv. Exotica. The effect of 6-benzylaminopurine (BAP), gibberellic acid (GA₃), indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on shoot growth and proliferationin vitro was investigated. Multiple shoots were developed after 3-4 weeks from stem internodes with axillary buds incubated in Murashige and Skoog (MS) medium supplemented with phloroglucinol (PG) and BAP. Optimum shoot proliferation took place in the presence of 1.0 mg l^-1 BAP. Shoots obtained could be elongated in a medium with 0.5 mg l^-1 GA₃ prior to their rooting. The root initiation was successfully induced on MS medium either with IAA at 0.5-0.1 mg l^-1 or in plant growth regulator-free medium. All rooted plantlets were subsequently transferred to a peat, humus and perlite mixture in a culture room with high humidity and covered with plastic bags. After one month the plantlets were established for growing in a greenhouse.

A fully habituated (H) nonorganogenic sugar beet callus, subcultured in the light, did not contain detectable chlorophyll (Chl) nor carotenoid (Car). It accumulated some Car in the dark. Fluorescence spectra indicated that this H callus also accumulated some protochlorophyllide which, however, was not well integrated into the protochlorophyllide-NADPH-photoreductase complex, and therefore not transformed into chlorophyllide in the light. The H callus showed no variable fluorescence which indicated absence of photosynthesis, and therefore it suggested a full heterotrophic behaviour of this peculiar callus line. A green hormone-dependent callus of the same sugar beet had normal fluorescence spectra and kinetics comparable to those of a green leaf.

Water and osmotic potentials were measured in young and mature styles of selfcompatible (SC) and selfincompatible (SI) species ofSolanaceae. For mature flowers, the stylar water and osmotic potentials were considerably lower in SI speciesNicotiana alata andPetunia hybrida than in SC speciesN. sylvestris andN. tabacum. Stylar water content (in % fresh mass) was also significantly lower in SI species (N. alata, P. hybrida, diploid clones of potato) than in SC species (N. acuminata, N. glauca, N. paniculata, N. sylvestris, N. tabacum). For flower buds younger than 2 d before anthesis, no differences in stylar water potential betweenN. alata (SI) andN. tabacum (SC) were observed. During further flower bud development the stylar water potential inN. alata decreased more expressively than inN. tabacum. Pollen culture in media with various concentrations of sucrose or polyethylene glycol revealed that optimal water potential for pollen tube growth was lower inN. alata than inN. tabacum. The differences were similar as for differences in stylar water potential. The results are considered in relation to possible involvement of stylar water potential in unilateral interspecific incompatibility inSolanaceae.

A series of binary vector plasmids derived from the T-DNA of theAgrobacterium tumefaciens strain C58, carrying the five plant morphoregulatory genes 1, 2, 4, 5 and 6b in different combinations, was used in the transformation ofNicotiana tabacum leaf discs. Protein patterns of the transgenic tobacco analysed through SDS-PAGE have shown changes in the polypeptides with M_r: ∼120, 60, 55, 43 and 27 kDa (for tobacco with transgene 4); ∼60, 55, 43, 26-25, 21, 18 kDa (for tobacco with transgenes 1, 2 and 5); ∼70, 60, 26, 25, 18 kDa (for tobacco with transgene 5); ∼60, 55, 48, 26, 18 kDa (for tobacco with transgenes 4, 5, 6b); ∼60, 55, 22 and 18 kDa (for tobacco with transgene 6b); ∼60, 55, 43, 26 and 18 kDa (for transgenes 5, 6b); ∼60, 55, 22, 18 and 16 kDa (for transgenes 4 and 6b). All types of transgenic plants showed quantitative changes in protein content. Mendelian segregation ratio to kanamycin resistance in the progeny of transgenic tobacco clones in the R1 generation was 3∶1 except in transgenic tobacco carrying transgenes 1, 2 and 5.

InAlysicarpus vaginalis (L.) DC. nitrogen, ascorbic acid, proline and epicuticular wax (ECW) contents were higher in the plants growing in the coastal region whereas the protein, soluble sugars and starch contents were lower. The higher contents of proline, nitrogen and ascorbic acid recorded in the plants of the saline habitat are a physiological adaptation to overcome the salt stress. The higher ECW content in the plants of the saline habitat specially in the summer months seems to be an adaptation in these plants to survive in the saline habitat.

The water use efficiency (WUE) of the C₃-C₄ intermediate speciesFlaveria anomala andF. pubescens was similar to that found inF. cronquistii (C₃). Compared to this values, the value inF. brownii (C₄-like) was significantly increased and was doubled inF. trinervia (C₄).Moricandia arvensis, a species with an enhanced CO₂ reassimilation potential has a very similar water use efficiency asM. moricandioides (C₃ but a lower transpiration rate.

The development of cleavage polyembryos of wheat, maize and radishin vivo andin vitro was compared. Some frequent features (such as common suspensors or suspensor-like structures, "concrescences", enlarged radicular meristems) suggest a similar origin of cleavage polyembryos inducedin vivo and those inducedin vitro from the proembryo. Cleavage of the original zygotic or somatic proembryo may occur either at a few-celled stage or later in the phase of radicular meristem establishment.

The embryonic axes of chickpea (Cicer arietinum) seeds were used to quantify 1-(malonyl)aminocyclopropane-1-carboxylic acid (MACC), 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene and some related enzymes during the initial 18 h imbibition period (anaerobic growth phase). Longer cold storage (stratification) of seeds produced higher levels of MACC and ACC. Maximum accumulation of MACC and malonyl-transferase activity occurred after 5 h of growth but MACC levels later became insignificant. ACC-synthase activity and endogenous ACC seem to reach a maximum 2 h after MACC accumulation. MACC-hydrolase activity was measured"in-vitro" and reached a maximum after 5.5 h of growth. These results suggest that endogenous MACC did not seem to be an end product; it may be involved in ACC production and the regulation of ethylene production before the emergence of the radicle. Ethylene-forming enzyme (EFE) activity reached a maximum after 12 h and ethylene production after 18 h of growth. The physiological implications of this temporal separation of MACC, ACC, ethylene and related enzymes is discussed.

Mesophyll derived protoplasts ofCatharanthus roseus cv. Little pinkie were fused with protoplasts derived from an habituated cell line ofC. roseus. Polyethylene glycol was used as agglutinating agent while fusions were induced by square pulses. Best results were obtained by fusing protoplasts from primary leaves with those from three-day-old cell cultures. Adding calcium ions considerably enhanced heterofusion rate. Good cell viabilities indicated that this fusion process was not cytotoxic. The heterofusion frequency was up to 10% or more. Most of the heterokaryons were able to regenerate their cell walls and underwent division.

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.

The effect of different NaCl regimes was examined on the growth and ion accumulation in whole plants and callus cultures ofVigna radiata. Whole plants grown in sand culture were watered with Hoagland's solution supplemented with 0-350 mol m^-3 of NaCl. Callus cultures were initiated from leaves of 7-d old seedlings of the same seed stock and grown in modified PC-L2 medium containing the same levels of NaCl as in Hoagland's solution. Callus showed the same tolerance to salt as did the whole plant suggesting thatV. radiata appears to have a mechanism(s) for salt tolerance which operates at the cellular level. Ion analysis of whole plant showed that root sodium concentrations of the tolerant cultivar G-65 was much higher while shoot sodium was much less than those of salt sensitive cultivar ML-1. Callus cultures of cv. G-65 also accumulated higher Na⁺ levels. Thus, the greater salt tolerance of cv. G-65 was associated with the control of sodium accumulation at the shoot or cellular level.

Chlorella fusca was subjected to evaporative dehydration under air humidity of 72%. Ca²⁺ pretreated cultures lost water as rapidly as untreated cultures. Nevertheless, an ameliorative effect of Ca²⁺ pretreatment in droughted cells was found as membrane stability index was improved and K⁺ leakage was reduced. In addition, higher chlorophyll content and stability was observed. These parameters enabled droughted cells to recommence growth upon rewatering. Thus Ca²⁺ might increase survival ofC. fusca cells subjected to drought through membrane stabilization.

Leaves ofQuercus serrata seedlings were sprayed with solutions of different concentrations of Mg, Zn and Mo-salts and activity of nitrate reductase (NRA) and soluble protein contents were determined in fresh leaves of different ages. The optimum dose for magnesium sulphate and zinc sulphate was 2.5 mM while for ammonium molybdate it was 0.01 mM. Under optimum doses of these nutrients high levels of NRA and protein contents were maintained upto 28 d of spray. Observations on NRA were further confirmed by leaf direct treatment and excised shoot-dipping experiments which showed maximum NRA at comparatively much lower concentrations of ions than those used for spray.