The individual and interactive role of calcium and abscisic acid (ABA) in amelioration of water stress simulated by polyethylene glycol (PEG) 6000 was investigated in two contrasting wheat genotypes. PEG solution (osmotic potential -1.5 MPa) was applied to 10-d-old seedlings growing under controlled conditions and changes in photosynthetic rate, activities of ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase, water potential and stomatal conductance were observed in the presence of 0.1 mM ABA, 5 mM calcium chloride, 1 mM verapamil (Ca²⁺ channel blocker), and 1 mM fluridone (inhibitor of ABA biosynthesis). ABA and calcium chloride ameliorated the effects of water stress and the combination of the two was more effective. The two genotypes varied for their sensitivity to ABA and Ca²⁺ under stress. As was evident from application of their inhibitors, ABA caused more alleviation in C 306 (drought tolerant) while HD 2380 (drought susceptible) was more sensitive to Ca²⁺.

Kiwifruit plants (Actinidia deliciosa cv. Hayward) were grown in Hoagland nutrient solution with calcium nitrate, potassium nitrate, ammonium nitrate or ammonium chloride as the nitrogen source. Plants grown in the solution with nitrate nitrogen displayed a higher oxalate content, greater shoot length and leaf area, and higher content of ascorbic acid and NO₃^- ions in the leaves. Plants grown in the solution with ammonium nitrate, and particularly with ammonium chloride, showed low oxalate content, low content of ascorbic acid and NO₃^-, high content of Cl^- and Na⁺, low shoot length and leaf area. Oxalate formation appeared to be connected with the assimulation of nitrate, more precisely with nitrate reduction, while ammonium nitrogen assimilation did not induce the synthesis of oxalic acid.

Nostoc rivulare was grown in batch cultures under controlled CO₂ and NO₃^- concentrations to modulate the photosynthetic source:sink relationship. Increasing CO₂ supply accelerated the accumulation of chlorophyll (Chl) a, i.e., supplemental CO₂ combined with double concentrations of NO₃^- more than doubled the amounts of Chl a relative to those of the original medium. Photosynthetic oxygen evolution and respiratory oxygen uptake were both enhanced by elevated CO₂ and NO₃^-. Contents of soluble sugars and starch (total non-structural saccharides) as well as insoluble saccharides (structural fraction) were affected by altering CO₂-NO₃^- combinations. Uptake as well as reduction of either NO₃^- or NO₂^- was inhibited by CO₂ deprivation. Expanding the sink size via increasing NO₃^- supply enhanced photosynthesis and thus the sink (NO₃^-) acted as a feed forward stimulator of the source (photosynthesis). The regulatory role of nitrate on photosynthesis was most influential in CO₂-deprived cultures since it could enhance photosynthesis to higher levels than CO₂-supplemented, nitrate-free cultures.

We determined the characteristics of phytochelatin synthase from tobacco (Nicotiana tabacum cv. Bright Yellow-2) cells, especially the conditions for the enzyme stability. From the results, we proposed the optimum assay conditions of the enzyme activity.

Seasonal dynamic of total nonstructural saccharides (TNS) and individual saccharides (starch, sucrose, glucose, fructose, fructans) was followed in rhizomes and stem bases of Calamagrostis epigeios (L.) Roth at two types of meadows communities in the South Moravia (Czech Republic): cnidion and molinion alliances, which differ in their water regime. The TNS were formed mainly by fructans and starch, while glucose, sucrose and fructose were low. The amount of TNS in rhizomes and stem bases of plants from wet cnidion site was higher than in plants from drier molinion site. The seasonal trends of all saccharides were similar in the both sites. During growing season (June to October) the main storage sugar was fructan (18 - 21 % of dry biomass). At the beginning of September the content of fructan decreased to 10 - 12 % and simultaneously the content of sucrose increased from 1 to 3 %. This may increase frost resistance. The content of TNS in the stem bases was lower than in the rhizomes. During winter time the stem bases contained 2 to 2.5 % of sucrose. Plant height and aboveground biomass were also higher in molinion site.

Using preparative isoelectric focusing, fast performance liquid chromatography, and polyacrylamide gel electrophoresis accumulation of several Al-induced cytoplasmic proteins was described in barley roots. Two of them, 27 and 28 kDa polypeptides were isolated by continuous-elution electrophoresis system in sufficient quantities for their further characterisation.

Araucaria bidwillii Hook. and Araucaria cunninghamii Don D. are two species of conifers whose seeds belong to different physiological categories: A. bidwillii seeds are recalcitrant, while A. cunninghamii seeds are orthodox. The extraction of enzymes and storage proteins was carried out from A. bidwillii and A. cunninghamii megagametophytes. The endopeptidase activities of both species were assayed with azocasein and with haemoglobin; the exopeptidase activities were detected by various N-carbobenzyloxy-dipeptides and L-leucine p-nitroanilide. The use of appropriate proteinase inhibitors, i.e. pepstatin A, ethylenediaminetetraacetic acid and trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane, showed the presence of aspartic and metallo proteinases and the absence of the cysteine ones both in A. bidwillii and in A. cunninghamii ungerminated seeds. Since the results do not show differences between the types of enzymes in the ungerminated araucarian seeds and those present in some ungerminated angiosperm seeds (barley, wheat, maize, rice, buckwheat), we conclude that their physiological role is similar. The electrophoretical analyses of soluble and insoluble storage proteins of A. cunninghamii showed patterns similar to those found in other gymnosperms, while the storage protein patterns of A. bidwillii seeds were rather atypical.

Spirodela punctata was cultivated on phosphate-deficient medium (-P_i) with racemic 1-amino-2-phenylethylphosphonic acid (PheP) as a source of P_i. The growth of duckweed was inversely correlated with PheP concentration. The growth of plants on medium -P_i with 0.1 M PheP was accelerated whereas with 0.001 mM PheP was slower than in -P_i control. PheP at low concentrations decreased loss of chlorophyll in comparison with -P_i plants. Content of anthocyanins decreased but activity of the extractable constitutive phosphatases of pH 6.0 and pH 7.5 increased along with increasing concentration of PheP in the medium. We suggest that S. punctata does not break P-C bonds but probably PheP interrupts processes involved in the regulation of P_i-starvation response.

Loss of chlorophyll (Chl) and carotenoids (Car) of leaves and changes in Chl fluorescence emission and polarisation, malondialdehyde (MDA) accumulation, and 2,6-dichlorophenol indophenol (DCPIP) photoreduction in chloroplasts of wheat seedlings grown under different irradiance and subsequently exposed to high irradiance stress (HIS; 250 W m^-2) were studied in mature and senescent primary wheat leaves. Faster rate of pigment loss was observed in leaves of moderate irradiance (MI; 15 W m^-2) grown plants, compared to high irradiance (HI-1 and HI-2; 30 and 45 W m^-2) ones when exposed to HIS. A relatively lower loss of Car in the plants grown in HI-1 and HI-2 exposed to HIS suggests HI adaptation of these seedlings. The slower rate of increase in the ratio of Chl fluorescence emission (F₆₈₅/F₇₃₅) also may suggest photoprotective strategy of HI grown seedlings. There was a positive correlation between MDA accumulation and Chl fluorescence polarisation. The DCPIP photoreduction activity in chloroplasts isolated from HI-1 and HI-2 grown plants exposed to HIS showed slower loss of electron transport activity compared to MI grown plants. These observations suggest that plants grown under higher irradiance have capacity to manage the excess quanta better than those grown under lower irradiance.

The present investigations were conducted to ascertain the influence of Pb₂₊ and Cd₂₊ both individually and in combination on selected enzymes of tricarboxylic acid (TCA) cycle. All the enzymes of TCA cycle examined (α-ketoglutarate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, malate dehydrogenase) were affected deleteriously by Pb₂₊ as well as Cd₂₊ and these metals in combination gave more or less an additive effect.

The present study was carried out to investigate the degree of leaf wetness and its capacity to retain water droplets in relation to leaf morphological characteristics of Valeriana jatamansi J. grown under open and shade habitats. Leaves developed in open habitats had less wettability but higher capacity to retain water droplets and more number of stomata than shade leaves. A significant positive correlation of contact angle (ϑ) were noticed with trichome length, droplet retention and wax content.

Transient expression of β-glucuronidase (GUS) in zygotic embryo axes of two cotton (Gossypium hirsutum L.) cultivars NHH-44 and DCH-32 was induced by Agrobacterium mediated transformation or by particle bombardment. For Agrobacterium transformation, disarmed A. tumefaciens strain GV 2260/p35SGUSINT was used. In cv. NHH-44, the maximum frequency of transient expression (14.28 %) was achieved on spotting Agrobacterium paste on the apical regions of the split embryo axes. The method resulted in a transformed callus line, which showed strong GUS activity. Integration of NPTII gene was confirmed by Southern analysis. Transgene expression by particle bombardment was achieved with p35SGUSINT and pIBGUS plasmids independently. The maximum frequency of GUS expression in 29.16 % explants was observed in cultivar NHH-44 with gold microcarriers (1.1 µm) when bombarded once with rupture disc of 7586 kPa at target cell distance of 6 cm. A transformed callus line was obtained when explants were bombarded with p35SGUSINT and cultured on Murashige and Skoog's medium supplemented with B₅ vitamins, 0.1 mg dm^-3 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea, 0.01 mg dm^-3 α-naphthaleneacetic acid, 3 % glucose + 50 mg dm^-3 kanamycin. High GUS activity was observed in callus tissue as well as in somatic embryo like structures achieved in liquid shake cultures.

Micropropagated shoots of Stackhousia tryonii were exposed (individually or in combination) to indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and 1-naphthalene acetic acid (NAA) at concentrations 1, 2 or 4 g dm^-3 with the view to induce rooting under ex vitro conditions. The treated microshoots were grown in a mist room for four weeks and assessed for survival, rooting percentage, number of roots and root length. The results showed that IBA at 2 g dm^-3 was most effective in inducing roots. Mixing of two or more auxins markedly reduced rooting percentage indicating antagonistic effects. The results demonstrated the potential of combining ex vitro rooting and hardening in one step, with view to reducing costs of multiplying plants via micropropagation.

For most plant species growing in polluted areas no mutagenicity assays are available. We have studied the possibility of using the alkaline protocol of the Comet assay as a method for detecting induced DNA damage in wildly growing weeds. The monofuctional alkylating agent ethyl methanesulphonate (EMS) was applied on leaves of 10 weed species (ordered according to the diameter of the nuclei): Arabidopsis thaliana, Convolvulus arvensis, Bellis perennis, Urtica dioica, Lamium album, Chenopodium rubrum, Plantago media, Poa annua, Taraxacum officinale, and Agropyron repens. With increasing concentrations of EMS (2 to 10 mM) the DNA damage, expressed by the averaged median tail moment values, significantly increased in nuclei of all weeds studied. Using the Head Extent parameter of the Komet version 3.1, we have measured the diameter size of the nuclei of the 10 weed species either immediately after the isolation of the nuclei or after 20 or 45 min of treatment with alkaline buffer (pH > 13). According to the increase of the diameter of the nuclei (including the formed "halo") resulting from the to alkaline buffer treatment, electrophoretic conditions (unwinding and electrophoresis time) for the Comet assay can be selected for the individual weed species.

The effect of brassinosteroids (BRs) on catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) activity in tomato leaf discs was analyzed at 25 and 40 °C. Tomato leaf discs were preincubated for 24 h in Petri dishes with 24-epibrassinolide (EBR) or a polyhydroxylated spirostanic analogue of brassinosteroids (MH5). Both concentrations (10.60 and 2.12 nM) of EBR and MH5 stimulated the activity of SOD at 25 and 40 °C, the MH5-stimulated increase of this enzyme activity was greater. Peroxidase activity was unaffected at 25 °C, while at 40 °C this activity was enhanced by both compounds. The changes in catalase activity markedly depended on the structure BRs, doses and temperature. The results suggest a possible role of EBR and MH5 in the reduction of cell damage produced by heat stress due to induction of enzymatic antioxidants.

Clones of Plumbago zeylanica were micropropagated using nodal culture. The application of random amplified polymorphic DNA (RAPD) in assessing the genetic integrity of the micropropagated plants was evaluated by polymerase chain reaction. Twenty arbitrary decamers were used to amplify genomic DNA from in vitro and in vivo plant material to assess the genetic fidelity. All RAPD profiles from micro-propagated plants were monomorphic and similar to those of field grown mother plants. No polymorphism was detected within the micropropagated plants.

Two-day-old protonemata of Funaria hygrometrica Hedw. growing in vitro were treated with 4 μM Pb (given as PbCl₂) for 48 h. After this time chloroplasts of apical cell were distributed in different way than in control. In the middle part of the cell they formed one line while in the top one, usually swollen, they were crowded and formed irregular group. The reasons of such chloroplast distribution were: 1) increase of plastid size, probably the effect of intensive accumulation of starch and appearance of characteristic protuberances, 2) decrease of cell inner space additionally intensified by thickenings of lateral walls, and 3) disturbances of microtubule number and array.

Toxic effects of aluminium are primarily root-related. This review deals with growth, morphological, and ultrastructural responses of root to aluminium, their diversity along the root axis, and in the root tissues. The cell elongation seems to be most sensitive and responsible for early inhibition of root elongation. Longer Al treatment is required to reduce cell division or to interfere with nucleic acids in the root apex. Alterations of root morphology include root thickening, disturbances of root peripheral tissues, and initiation of lateral roots closer to the root tip. Ultrastructure alterations depend strongly on position of the cells with respect to the Al source, and on their developmental stage. Cell elongation and cell ultrastructure including organisation of cytoskeleton are most sensitive within the distal part of the transition zone of the root apex. This correlates with the rate of uptake and accumulation of Al along the root apex. Recognising the diverse responses and the most sensitive sites within the root apex can help in elucidating the mechanism(s) of Al effects on plants.

Wheat (Triticum aestivum L.) cultivars GK Tiszatáj, Yubileinaya, GK Öthalom and a landrace Kobomugi were grown for 18 d in hydroponic cultures containing 0 (control), 0.1, 1.0 or 10.0 µM Cu²⁺. On a dry mass basis, cvs. Tiszatáj and Kobomugi accumulated slightly more Cu²⁺ in the root tissues than did cvs. Yubileinaya and Öthalom, but their controls also contained higher amounts of Cu²⁺. As a result of perturbation in the plasma membrane functions the K⁺ content of roots was reduced at 10 µM Cu²⁺ in all cultivars, whereas the K⁺/Na⁺ ratio decreased significantly only in the roots of cv. Öthalom. In the sensitive cultivar, Öthalom, the dry mass of the roots decreased while the cysteine content, which is a limiting factor for glutathione synthesis, did not satisfactorily increase with increasing tissue Cu²⁺ content. This suggests that in cv. Öthalom the membrane damage of the root cells at 10 µM Cu²⁺ concentration may affect the sulphur availability or metabolism. Concentrations of glutathione and hydroxymethyl-glutathione, a tripeptide which may play a similar biochemical role to glutathione, were also lower in the sensitive cultivar. In the absence of glutathione the root tissues failed to cope with the oxidative stress caused by the excessive amount of Cu²⁺. A significant accumulation of iron in the roots of the sensitive cultivar at 10 µM Cu²⁺ supply enhanced the oxidative damage.

Abscisic acid (ABA) content and relative water content (RWC) in second fully expanded leaves of cold hardened plants and in dehydrated leaves of freezing tolerant barley (Hordeum vulgare L. cv. Lunet) were compared. ABA content and RWC in leaves did not change during the first day of cold hardening. On the contrary, dehydration of leaves led to a decrease of RWC and to an increase of ABA content.

Pyruvate kinase is an important enzyme of glycolytic pathway that also functions in providing carbon skeleton for fatty acid biosynthesis. It has been purified to near homogeneity from Ricinus communis, Selenastrum minutum, Cynodon dactylon, Brassica campestris and B. napus, and characterised. Partially purified preparations are reported from several other sources. A phosphoenolpyruvate (PEP) phosphatase accompanies pyruvate kinase. In plants, two isozymes of pyruvate kinase are reported, namely cytosolic and plastidic. Isoforms of cytosolic pyruvate kinase have also been reported from spinach. In most cases pyruvate kinase is a tetrameric protein and the molecular mass lies between 200 to 250 kDa. The pH optimum is in the range of 6.2 to 7.5. It requires both Mg²⁺ and K⁺ for maximum activity. ATP, citrate, and oxalate inhibit pyruvate kinase in most cases. A sequential compulsory ordered mechanism of binding of substrates to the enzyme has been proposed.

Heat shock (HS) reduced total lipid and phospholipid contents and their synthesis in germinating seeds of pigeonpea [Cajanus cajan (L.) Millspaugh]. Lipid peroxidation was also enhanced with increasing temperature and HS duration. HS influenced lipid metabolism to a higher extent at 45°C than at 40°C. This altered lipid metabolism and lipid peroxidation was associated with the loss of various solutes from the germinating seeds, and modification of growth and development. Pretreatment of germinating seeds at 40°C for 1 h or at 45°C for 10 min followed by incubation at 28°C for 3 h prior to 45°C for 2 h ameliorated solute leakage due to reduced lipid peroxidation and improvement in lipid content and membrane function.

Influence of increased K supply on growth and nutrient content in pearl millet (Pennisetum glaucum) under severe water stress was assessed in a pot experiment under glasshouse conditions. Nineteen-day-old plants of two lines, ICMV94133 and WCA-78 were subjected for 30 d to 235, 352.5, and 470 mg(K) kg^-1(soil) and two water regimes (100 and 30% field capacity). Increasing soil K supply did not alleviate the adverse effect of water deficit on the growth of two lines of pearl millet. Accumulation of N and K in the shoots of both lines was higher under water deficit than that under well-watered conditions, but such effect was not observed for P or Ca.

The effect of storage conditions on the serological activity of two isolates of potato virus Y^NTN strain (PVY^NTN) was studied by ELISA. Purified virus, intact and homogenized infected leaves stored freeze-dried and frozen at various temperatures were tested. Purified virus was the most stable at +4 °C and non-purified virus was best preserved as a freeze-dried leaf homogenate at -20 °C. Their serological activity did not change after three months of storage.