The acclimation potential to high irradiance of two cultivars of watermelon, Reina de Corazones and Toro, calculated as the ratio of sun vs. shade activities of O₂^- and H₂O₂ scavenging enzymes and non-radiative energy dissipation, was similar. However, Reina de Corazones exhibited a higher capacity in absolute terms for photoprotection (harmless dissipation of absorbed light energy at PS 2 and ascorbate and O₂^- and H₂O₂ scavenging enzymes) suggesting a larger resistance of this cultivar to high irradiance. This could be seen as smaller decreases in fruit productivity and in lower oxidative injury as probed by malondialdehyde content in sun plants of Reina de Corazones than in Toro plants. Additionally, the results show that shading might be beneficial to both cultivars, presumably because it reduces the susceptibility of high irradiance-induced stress.

Carrot cell suspension culture prior to immobilization by glutaraldehyde was permeabilised by Tween 80. The values of pH optimum for L-alanine aminopeptidase, L-proline iminopeptidase, and L-arginine aminopeptidase were 8.2, 7.4, and 7.9, respectively. The immobilized cells showed significantly lower aminopeptidase activity when compared to untreated cells. Alginate hydrogel was successfully used for immobilization of carrot cells retaining the activity of some aminopeptidases.

Genetic analysis with T-DNA mutants often brings difficulties resulting from instability of the transgenic phenotype. In this work three different Arabidopsis thaliana T-DNA embryonic lethals and one T-DNA morphological mutant were analyzed in F2 progeny after 15 different crosses with marker lines for individual chromosomes. F2 analysis of 44 segregation ratios revealed segregation distortion of similar character consisting in abnormal excess of nontransgenic plants to the detriment of transgenic ones. We quantified this phenotypic drift (d) on the basis of phenotypic ratios given the respective formulas. The d values indicate the rate of F1 gametes which loose the T-DNA mutation or ability of its expression. The obtained d value were relatively high, 0.4 to 0.9 for individual crosses. It makes the standard recombination analysis with insertional mutants very problematic or even impossible.

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was used for monitoring Al-induced changes in polypeptide composition of membrane proteins isolated from 3-d-old maize seedlings subjected to aluminium stress. Analysis of peripheral membrane proteins isolated from maize root showed an Al-induced increase in accumulation of 14 polypeptides with apparent molecular mass from 10 to 135 kDa. Qualitative differences were found between peripheral membrane proteins isolated from root tip (increased accumulation of 4 polypeptides with M_r 42 000 - 135 000) and from root base (increased accumulation of 10 polypeptides with M_r 10 000 - 59 000). On the other hand, no Al-induced changes were observed in peripheral membrane proteins isolated from maize coleoptile and integral membrane proteins isolated either from root or coleoptile. These results indicate that peripheral membrane proteins undergo considerable changes during 24-h Al treatment while integral membrane proteins pattern is stable.

The morphogenetic responses of cotyledonary nodal explants of Vigna mungo (L.) Hepper cv. VBN1 cultured on the same Murashige and Skoog's medium, B5 vitamins, and 13.31 µM N⁶-benzylaminopurine showed variations in the pattern of multiple shooting and morphology of leaves in dependence on initial explants (presence/absence of cotyledons). The regenerated shoots elongated in the initial medium and most of them rooted in the presence of 2.41 µM indole-3-butyric acid, and flowered in vitro. Rooted plants could be transferred to the field after hardening.

The patterns of esterase and peroxidase isoenzymes, subunits of zein-2 fraction and protomers of SDS-protein complex of Zea mays L. × Tripsacum dactyloides L. hybrids and their parents were compared. The study has been made to detect specific to Tripsacum isoesterases and isoperoxidases, zein subunits and SDS-protein protomers which could be used as markers for introgression of gene loci encoding these proteins from Tripsacum into hybrids of Tripsacum with Zea mays. Isoesterases and isoperoxidases as well protomers of SDS-protein complex specific to Tripsacum were detected in all hybrids analyzed. Zein subunits, specific to Tripsacum were detected in some of the analyzed hybrids which i that introgression frequency of the loci encoding proteins studied was different. Chromosome counts taken on the examined hybrids showed the addition of 9 - 13 Tripsacum chromosomes to maize chromosome complement.

Seedlings of green gram [Vigna radiata (L.) Wilezek] cultivar KM-2 were sprayed with different concentrations of triacontanol (TRIA) (0, 0.5, 1.0, and 2.0 mg dm^-3) at 15 and 25 days after sowing. Foliar spray of 0.5 mg dm^-3 TRIA significantly promoted the plant height, fresh mass, and contents of chlorophylls, saccharides, starch, soluble proteins, amino acid and phenols. Leaf nitrate content was reduced by 0.5 and 1.0 mg dm^-3 TRIA with a corresponding increase in nitrate reductase activity. TRIA of 0.5 mg dm^-3 stimulated the onset of flowering, pod production and retention, but less number of pods and seeds per plant were observed at 2.0 mg dm^-3 treatment.

The effect of low temperature on the protein metabolism of wheat primary leaves was examined. In seedlings transferred from 25 to 5 °C, total soluble protein accumulation, in vivo protein synthesis and breakdown, in vitro protein breakdown, and SDS-PAGE profiles of proteinases in gelatine-containing gels were analysed. Leaf protein content increased within a 7-d period (70 % over the initial value) in plants exposed to 5 °C. The fast protein accumulation observed on days 0 - 2 was mainly attributed to a decreased breakdown. In further days, parallelly to a slowdown in the rate of protein accumulation, the leaf proteolytic activity increased. The incubation temperature also had an influence on the proteolytic activity: Q ₁₀ values for the 15 - 5 °C range were 80 - 200 % higher than those observed for the 25 - 15 °C range. On the other hand, the in vivo protein synthesis capacity, at either 25 or 55 °C, was not significantly modified in cold-treated plants. In addition to the enhanced activities of two serine-proteinases (previously found in control plants by SDS-PAGE analysis), cold-treated plants displayed a new proteinase, which had not been detected so far.

Expression of esterase isozymes from cloves of bolting and non-bolting garlic clones belonging to winter and summer ecotypes were analyzed. The isozyme patterns were obtained by means of vertical block electrophoresis in polyacrylamide gels. Quantitative and qualitative differences between loci of winter and summer garlic ecotype were found. This fact substantiates application of the isoesterases for identification of garlic clones.

In order to control young plant form by modifying culture conditions, plants of Rhododendron catawbiense from in vitro culture were grown in a greenhouse under different photoperiodic treatments (long or short days) combined or not with a several-week nitrogen starvation. After 12 weeks of culture under long days (16 h) with nitrogen supply, plants showed a rhythmic acrotonous development. When long days were combined with a six-week nitrogen starvation, the apical growth pause was extended leading to an increase of the number of acrotonous lateral ramifications. Short-day (8 h) treatment affected distal burst potential and moreover when a concomitant nitrogen starvation was applied. This lack of distal development allowed basal buds swelling, leading to basitonous plants. When plants were returned back to long days after 2, 4 or 6 weeks under short days, distal buds resumption competed with basal shoots development. Durable basitonous plants were obtained by a 12-week short days treatment combined with a 6-week nitrogen starvation.

Maintenance respiration rate, R_M, irrespective of growth stages, increased with increase in nitrogen supply. The R_M increased almost in proportion with net photosynthetic rate, P_N, and biomass production during early growth stages, while it declined after anthesis. Significant positive correlation was observed between biomass production and P_N at all growth stages except tillering. Though R_M was positively correlated with biomass production during early growth stages, it was negatively correlated with the rate of increase in shoot biomass after flowering, which could indicate a possibility to identify certain cultivars endowed with low maintenance expenses despite building up biomass.

The effect of 0.5 mM salicylic acid (SA) pretreatment and of growing at hardening temperatures on chilling-induced changes in 1-aminocyclopropane-1-carboxylic acid (ACC) and malonyl 1-aminocyclopropane-1-carboxylic acid (MACC) was investigated in young maize (Zea mays L.) plants grown in hydroponic solution at 22/20 °C. Chilling at 5 °C caused an increase in ACC content;however, this increase was less pronounced in plants cold acclimated at 13/11 °C 4 d before the chilling treatment, and in those which were pretreated with SA for 1 d before the cold stress. Changes in MACC at low temperature showed no correlation with chilling tolerance in maize.

Changes in the content of soluble sugars and starch were determined during the first phase of de novo organogenesis in stem internode segments (SIS), taken either from control plants or from the plants grown on medium with 10^-8 M paclobutrazol (PBZ). Transient accumulation of soluble sugars was observed in both variants during the first two days. Control SIS accumulated higher amount [22.0 mg g^-1(f.m.)] of soluble sugars than the PBZ pretreated SIS [15.2 mg g^-1(f.m.)]. PBZ variant showed four times higher starch content at the start of experiment in comparison with the control. Both variants accumulated starch during cultivation until the beginning of regeneration.

Isoenzyme analysis and activities of peroxidase (PER), polyphenol oxidase (POD) and glutamate oxaloacetate (GOT) and randomly amplified polymorphic DNA (RAPD) fingerprints were used to analyze somaclonal variations in tissue culture-derived date palm plants. The frequency of somaclonal variations was found to be age dependent. Similar isoenzyme patterns for PER and GOT were detected in all analyzed plants. However, variations in activities of the three enzymes studied and in POD isoenzymes were detected. RAPD analysis showed genetic variations in approximately 4 % of the analyzed plants (70 regenerants). The genetic variations were only detected in 6- and 12-months-old cultures. It was observed also that all morphologically abnormal shoots showed genetic variations at the molecular level.

Salinity reduced mung bean (Vigna radiata Wilczek) radicle and root elongation, delayed and inhibited hypocotyl elongation and mobilization of reserves from the cotyledons to the embryo axis. Fresh and dry masses and water content of the embryo axes were reduced. Under salinity, a net leakage of K to the media increased with time and increasing NaCl concentrations. Sugars present in the cotyledons of seeds were of primary importance for growth of the embryo axis upto 18 h after sowing whereas breakdown of starch by amylase contributed later, the contribution being delayed and reduced with increasing NaCl concentration. Even when amylase activity in the cotyledons was progressively reduced with increasing NaCl concentration, the increasing contents of soluble sugars in the cotyledons indicated that sugars were not limiting for mung bean seedling growth under salinity.

Embryogenesis can be initiated directly from microspores or pollen grains. This is known as androgenesis and refers to the process of redirection of normal pollen development (gametophytic pathway) towards the embryo formation (sporophytic). This review mainly deals with the current knowledge of stress and developmental aspects of induction of androgenesis. The crucial role of stress inductive treatment together with changes in cell polarity are discussed in relation to other relevant biological systems. The intriguing speculations are made on the basis of these comparisons which may point out the direction of future investigations.

The effect of two N-forms (NH₄⁺ and NO₃^-) and NaCl on pattern of accumulation of some essential inorganic nutrients was examined in sunflower (Helianthus annuus L.) cv. Hisun 33. Eight-day-old plants of were subjected for 21 d to Hoagland's nutrient solution containing 8 mM N as NH₄⁺ or NO₃^., and salinized with and addition of NaCl to the growth medium had no significant effect on total leaf N. However, root N of NH₄-supplied plants decreased significantly with increase in NaCl concentration, whereas that of NO₃-supplied plants remained unaffected. There was no significant effect of NaCl on leaf or root P, but the NO₃-supplied plants had significa concentration of leaf P than that of NH₄-supplied plants at varying salt treatments. Salinity of the rooting med did not show any significant effect on Na⁺ concentrations of leaves or roots of plants subjected to two differen N. NH₄-treated plants generally had greater concentrations of Cl^- in leaves and roots and lower K⁺ content in leaves than NO₃-supplied plants. Ca²⁺ concentrations of leaves and roots and Mg²⁺ concentrations of leaves decreased in NH₄-supplied plants due to NaCl, but they remained unaffected in NO₃-treated plants.

Various ecophysiological investigations are presented in Aldrovanda vesiculosa, a rootless aquatic carnivorous plant. A distinct polarity of N, P, and Ca tissue content per dry mass (DM) unit was found along Aldrovanda shoots. Due to effective re-utilization, relatively small proportions of N (10 - 13 %) and P (33 - 43 %) are probably lost with senescent leaf whorls, while there is complete loss of all Ca, K, and Mg. The total content of starch and free sugars was 26 - 47 % DM along adult shoots, with the maximum in the 7^th - 10^th whorls. About 30 % of the total maximum sugar content was probably lost with dead whorls. The plant was found to take up 5 - 7 times more NH₄⁺ to NO₃^- from a mineral medium. Under nearly-natural conditions in an outdoor cultivation container, catching of prey led to significantly more rapid growth than in unfed plants. DM of the fed controls was 48 % higher than in the unfed plants. The controls produced 0.69 branches per plant, while the unfed plants did not produced any. However, the N and P content per DM unit increased by 6 - 25 % in the apices and the first 6 whorls in the unfed variant, as compared to the fed controls. It may be suggested that carnivory is very important for Aldrovanda.

An experiment was conducted with three wheat (Triticum aestivum L.) genotypes C 306, HD 2285 and HD 2329 (differently susceptible to water and temperature stress) to study the extent of oxidative injury and activities of antioxidant enzymes in relation to heat stress induced by manipulating dates of sowing. Increase in temperature by late sowing significantly decreased leaf relative water content (RWC), ascorbic acid content, and increased H₂O₂ content and lipid peroxidation in all the genotypes at 8 and 23 d after anthesis. Temperature tolerant genotypes C 306, closely followed by HD 2285 were superior to HD 2329 in maintaining high RWC, ascorbic acid content, and lower H₂O₂ content and lipid peroxidation (malondialdehyde content) under high temperature (late sowing) at the two stages. Activities of superoxide dismutase and catalase were highest in HD 2285 followed by C 306 and minimum in HD 2329 while ascorbate peroxidase activity was highest in C 306.

The objective of this research was to investigate how ferulic and p-coumaric acids affect lipid and fatty acid composition during canola (Brassica napus L.) seed germination. Data showed that both compounds increased total lipid and fatty acid contents in the cotyledons during germination. The largest accumulation in lipids occurred at 1.0 mM p-coumaric acid with an increase in all unsaturated fatty acids. The results suggest that allelochemicals interfere in canola seed germination by reducing lipid mobilization.

Barley (Hordeum vulgare L. cv. Hassan) leaves were used to study the effects of developmental stage and photoperiod on the NAD(P)H-ferricyanide oxidoreductase (NAD(P)H-FeCNR) and on the photosystem (PS) 1 and 2 activities of isolated chloroplasts. From day 6 to day 12, both the PS 1 and NADH-FeCNR activities decreased while NADPH-FeCNR activity remained almost unchanged. Methyl jasmonate had no significant effect on the NAD(P)H-FeCNR activity changes. In 6- to 7- and 14- to 15-d-old plants, the NADH-FeCNR activity was higher during the photoperiod than during the dark period and, in the 14- to 15-d-old plants, the PS 1 activity increased during photoperiod in the same way, but to a lesser extent. The PS 1 activity of plants during a dark-accelerated senescence was low. The simultaneous changes in chloroplast PS 1 and NADH-FeCNR activities support the role proposed for the chloroplast NADH dehydrogenase complex in the cyclic electron transport.

Tobacco (Nicotiana tabacum L., cv. Samsun) leaf discs inoculated with tobacco mosaic virus (TMV) were treated with auxin-like herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 3-amino-1,2,4-triazol (Amitrol) and 6-chloro-2-ethylamino-4-isopropylamino-1,3,5-triazine (Atrazin). All herbicides in the concentration of 10^-7 M enhanced the virus content (MCPA to 227.4 %, Amitrol to 218.1 % and Atrazin to 257.3 % of values found in TMV-infected, herbicide untreated discs). The 2,4-D alone did not affect the activity of the glucose-6-phosphate dehydrogenase and ribonucleases, but the 2,4-D treatment together with TMV infection raised their activities twice as high as in the untreated control discs. Polyacrylamide gel electrophoresis of acidic extracellular proteins washed from leaf discs treated with 2,4-D did not prove the induction of PR-proteins.