Leaves of drought-resistant and drought-sensitive genotypes of maize (Zea mays L.) were sprayed with ethephon to determine its effect on water and osmotic potentials. With both sufficient and limited water supplies, ethephon decreased the water potential, but not the osmotic potential, of the drought-sensitive maize. It had no effect on the water and osmotic potentials of the drought-resistant maize under either water regime. The results showed that the response of a genotype of maize to ethephon depends upon its susceptibility to drought.

The contet of phenols, o-dihydroxyphenols and peroxidase activity in healthy andCurvularia andropogonis (Zimm.) Boedijn infected leaves ofJava citronella were determined. As a result of infection, the content of phenols and peroxidase increased two- and four-fold, respectively in necrotic lesions compared to healthy leaves. In surrounding tissue of lesions, their increase was one-and half fold only. The peroxidase activity decreased with the maturity of the necrotic lesions. Necrotic lesions produced in response to infection appear to be the consequence of higher accumulation of phenols and their oxidation by peroxidase.

Potassium (K⁺) and nitrogen (N) supply affect stomatal apertures within the daylength conditions. There is a negative proportion between potassium supply and stomatal pore area: the smallest pores were to be found in the plants with K⁺ surplus, whereas the plants in K⁺ shortage had the largest pores. This is interpreted as a reaction of the plant to get more ions by an increased transpiration stream. With different nitrogen concentrations in the supply solution a similar proportion could be found, with the exception of the condition "N shortage in shortday", and further testing is necessary. The ionic supply has a parallel effect in both daylengths.

Arabidopsis thaliana tumors were induced by octopine strain ofAgrobacterium tumefaciens B6S3 and its derivatives with modified T-DNA. Flowering shoots appeared sponta-neously onin vitro cultivated tumors and set seeds. R₁ and R₂ progeny of octopine synthesizing plants segregated in opine synthesis activities 3:1 and 15:1. Octopine synthase activity showed absolute linkage with agropine synthesis in most lines. In R₃ and R₄ progenies, the fraction of octopine synthase and agropine synthesis positive plants was lower than expected, but Mendelian segregation was restored if plants were cultivated on medium with 5-azacytidine. The most probable mechanism of disapearance of opine synthesis is cytosine methylation. The effect of 5-azacytidine lasted for at least next two generations.

Phosphoenolpyruvate carboxylase (PEPC) was isolated from maize seeds which were germinated for 20 h, using a procedure which included extraction of seed homogenate with Tris-HCl or sodium phosphate buffer, precipitation of the extract with ammonium sulphate, chromatography on DEAE cellulose, and gel filtration on Sephadex G-200. Phosphate buffer was found to be less suitable than Tris-HCl buffer both for maize seed extraction and for further PEPC purification steps. The enzyme preparation obtained was electrophretically homogenous. PEPC activity was inhibited by both phosphate and malate. It values obtained at pH 8.1 which is the pH optimum of the reaction equelled to 42 mmoll^-1 for phosphate and to 13 mmoll^-1 for malate. PEPC isolated from germinating maize seeds was activated by glucose-6-phosphate, glucose-1-phosphate, ribulose-l,5-bisphosphate, fructose-1,6-bisphosphate, and fructose-2,6-bisphosphate. The authors intend to elucidate the mechanism of PEPC activation by sugars by means of the application of a number of derivatives of the sugar phosphates, among which for example 2-deoxy-2-fluoro glucosephosphate also activated PEPC. Sugar phosphates activated PEPC isolated from germinating maize seeds in this order, with increasing effect: fructose-l,6-bisphosphate, glucose-1-phosphate, glucose-6-phosphate, 2-deoxy-2-fluoro glucosephosphate, ribulose-l,5-bisphos-phate, fructose-2-6-bisphosphate.

Amphistomatous C₃ (Nicotiana tabacum L., Datura stramonium L.) and C₄ (Sorghum saccharatum Pers. and Zea mays L.) species were examined to find how (if at all) their inherent differences in water-use economy are reflected in apparent cuticular transpiration or vice versa. Transpiration efficiency (TE) was calculated from steady state photosynthesis (A) and transpiration (E) rates estimated for the upper side of the leaf after light induction of stomata opening. Apparent cuticular transpiration ('E_c) was measured as the part of transpiration which was not eliminated by convective counteraction of the air stream passing across the amphistomatous leaf: total pressure difference (AP) across the leaf was increased and the minimal value of E_ΔPτ0 was taken as the apparent cuticular transpiration rate ('E_c). 'E_c was treated relative to E at AP equal to zero (E_GDP=0), E'_cr. Measurements were carried out under two leaf-air vapour pressure differences (VPD).
E_r (i.e. E_GDPτ0/E_GDP=0) versus GDP patterns differed qualitatively between the investigated C₃ and C₄ plants. TE increased and 'E_cr decreased from tobacco, stramony, maize to sorghum for both VPD of air. 'E_cr and TE were approximately linearly related, the slope being dependent on VPD. The increase in VPD resulted in larger E and slightly smaller epidermal conductance (g) at GDP equal to zero. Both E'_cr and E'_cr decreased markedly at the same time especially, for species with high TE. The results were considered as an indirect confirmation that E'_c values estimated by the technique used reflect species-specific differences in external peristomatal and cuticular vapour loss, at least in a relative sense.

The transaminations of L-tryptophan (L-trp) and of L-phenylalanine (L-phe) are catalysedin vitro by the same non-specific aminotransferase. The transaminations procceed at the same pH (pH 8.5) and temperature (45 °C) optima, have parallel increases in activity with addition of the coenzyme pyridoxal phosphate (PRP) and have identical elution characteristics in gel chromatography. The enzyme from pea seedlings has a relatively weak affinity for both amino acids (K_m L-trp = 4.16 × 10^-1 mmol 1^-1; K_m L-phe = 2.10 × 10^-1 mmol 1^-1). Differences in affinity for a series of keto acids in the pea enzyme were observed, with pyruvate having the strongest and glyoxylate the weakest affinity. Transamination of L-trp and L-phe was demonstrated by enzyme extracts from pea, maize and tomato, but was not detected in kohlrabi. The amino acids L-asparagine (L-asn), L-phe, L-lysine (L-lys), L-methionine (L-met) have distinct inhibitory effects on the transamination of L-trp. Indolylacetylaspartate and tryptophol were shown to be competitive inhibitors. The regulation at the molecular level of L-trp transaminase activity is discussed.

Lead chloride (10^-5 M) inhibited the growth of the main root, the duration of development, the number and growth of lateral roots, primary and trifoliate leaves, and also the mitotic index in root apical meristems. Lead strongly inhibited root growth rate, mainly by reducing the number of dividing cells. Other mechanisms of this inhibition are discussed.

A NADH-ferricyanide reductase activity found in radish microsomes isolated from germinated seeds has been shown to be stimulated by pCMB and pCMBS which are both strong nactivators of many plant proteolytic enzymes. In the same preparation a leucine aminopeptidase was found while endoprotease and carboxypeptidase activities were not detected using exogenous substrates. The aminopeptidase, highly active at the same optimal pH-condition of FeCN reductase, was stimulated by CoCl₂ and non-polar detergents (Triton X-100 and Brij 35). It was inhibited by sulphydryl reagents. By gel filtration of microsomal detergent extract two peaks of activity were separated: red I coeluted with LeuAPase and red II, free of aminopeptidase. Red I, a protein, was inhibited by sulphydral reagents and stimulated by duroquinone. Red II, stimulated by pCMB, is not a protein because of the small size and the noninfluence of heating treatment on catalytic activity.

Several tomato cultivars were infected with a severe strain of PSTV and a pathophysiological reaction was characterized by means of enzyme-linked immunosorbent assay with serum containing IgGs to disease-associated host-specific leaf proteins. A strong expression of disease-associated symptoms (stunting, epinasty, leaf blade malformation and rugosity) and strong immunochemical reaction was found for cultivars Bizon, Linia, Revermun and Rutgers. The immunochemical assay revealed appearence of a major antigenic protein having a molecular mass of about 70 kD in these cultivars. The immunochemical reaction with disease-associated proteins reached a maximum four weeks after inoculation of PSTV. A weak immunochemical reaction was observed, if proteins from cvs. Sonato, Harzfeuer and Karlik were analyzed. Cvs. Sonato and Harzfeuer did not show characteristic symptoms such as stunting, leaf blade malformation and rugosity. Except for stunting, the same was true for cv. Karlik. On the other hand, no significant difference in PSTV accumulation was observed among the cultivars analyzed.
Reciprocal hybrids obtained by crossing cvs. Revermun and Karlik showed strong symptoms of the disease (Revermun-type) and increased activity of nuclease due to PSTV infection. On the contrary, an immunochemical analysis revealed a low level of the disease-associated antigens in these hybrid tomatoes, suggesting rather recessive genetic background determining their expression during PSTV-caused pathogenesis.

Twenty one winter wheat(Triticum aestivum L.) genotypes classified as (1) short, (2) medium or (3) tall were grown in field trials. The following parameters have been measured on the main stem: stem length, peduncle length, dry mass and conducting system parameters including number of vascular bundles and their total and phloem area on peduncle cross section, ear yield and its components. Regardless of differences in peduncle length among the genotypes groups differing in stem length, the peduncle relative length varied only between 36 and 38 % of the total stem length. Nearly identical was also the peduncle specific dry mass reaching 7.4 to 7.6 mg (dry mass) per cm (peduncle length).
The highest number of vascular bundles as well as the largest bundle and phloem area per peduncle cross section were found in the group of short cultivars. There was a positive correlation between the anatomical parameters and kernel number or dry mass per spike. The relationships need not be valid with each genotype because the final ear productivity is subjected to climatic variation well after anthesis when the formation of the stem anatomy has been by far accomplished.

Previous results with potato leaf tissues revealed that a treatment with ABA (10^-4 M) induced an increase of K⁺ uptake (Suleimanet al., 1990a).
In this study, we investigate the relationship between increased K⁺ uptake, Ca²⁺ fluxes and calmodulin by treating potato leaf discs with Ca²⁺ channel blockers (La³⁺, verapamil and nifedipine) and with calmodulin inhibitors (chlorpromazine, W₇: N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide, and compound 4880).
We found : a) all these inhibitors decreased K⁺ uptake in the same ratio in tissues treated or not with ABA; b) a synergistic effect between ABA and the Ca²⁺ ionophore A 23187 on K⁺ uptake.
The results suggest that the hormone may act on K⁺ uptake like a Ca²⁺ agonist, in accord with HUDDART's hypothesis.

Vegetation experiments were conducted under greenhouse conditions in which long-term effects of simulated acid rain on the shoots, and short-term effects of acidified root medium on the roots of two maple species (Acer pseudoplatanus L. andAcer negundo L.) were studied. Both alternatives of the acidification stress were studied with respect to exogenous applications of auxins and gibberellins. Changes in seedling growth caused by acid rain were not marked, but changes in the levels of endogenous growth regulators were detected, both the long-term exposure ofAcer pseudoplatanus L. seedling shoots to acid rain and the short-term acidification of root environment resulted in enhanced cytokinin activity and in decreased gibberellin activity. But when A.pseudoplatanus L. seedlings were pretreated with gibberellins, their activity was further increased by increased acidity.Acer negundo L. seedlings responded to the acidification of their root environment with enhanced cytokinin activity only when pretreated with exogenous auxins. The differences in the responses ofA. pseudoplatanus L. and A.negundo L. to the acidification can be explained in terms of their distinct physiological properties, including changes recorded in chlorophyll content. The results obtained show that a pretreatment of maple seedlings with exogenous growth regulators can modify the effects of increased acidity in the environment on their physiological status as characterized by the level of endogenous cytokinins and gibberellins.

The synthesis of major storage globulin polypeptides has been examined in developing seeds of sunflower(Helianthus annuus L.). Analyses of total proteins and purified globulins, also called helianthinin, by gel electrophoresis and immunoelectrophoresis have shown that a burst of protein synthesis and accumulation occurs around 10 d after flowering. There is no mature globulin before that time and only small amounts of precursor forms can be detected. Thus, 10-12 d after flowering appears to be a transition period during which genetic information for the globulin becomes actively expressed. Immunoelectrophoresis has confirmed that globulin is the main storage protein, at seed maturation, accounting up to 70 % of total proteins per kernel. Pulse chase experiments have shown that synthesis initially involves the formation of high molecular mass precursors and that storage proteins are post-translationally processed. Intermediary products, with molecular mass higher than early translational products, can be detected, together with mature globulin polypeptides.

Fruit epidermis ofMusa (AAB) cv. Poovan (S) remains single-layered throughout its development. There is no change in stomatal number but its frequency and index decrease due to slight increase in epidermal cell number and size. The external wall of the epidermal cells shows stratification of wall layers that is characteristic of normal epidermal cell with cuticle and epicuticular wax deposits. Surface wax deposits show qualitative and quantitative variations during fruit development and ripening.

The effects of chlorpromazine and calmidazolium on rapid IAA- and GA₃-induced changes in growth rate of etiolated pea stems were measured. During the initial period of up to 160 min after hormone application, the responses to both IAA and GA₃ were seen to be biphasic, showing two acceleration peaks. Chlorpromazine or calmidazolium applied simultaneously with the hormones blocked the first IAA-induced acceleration peak, but did not affect the second one. In contrast, the first GA₃-induced peak was not prevented by chlorpromazine or calmidazolium, while the second one was completely abolished. The results support the concept that the active calmodulin-calcium complex may be an essential component of hormone-controlled stem elongation. They also point to differential mechanisms of IAA and GA₃ actions.

Trans-resveratrol (4,3',5'-trishydroxystilbene) was identified in grapevine leaves with vein necrosis disease symptoms. The compound accumulates from 10 to 60 μg^-1 (fresh mass) in infected leaves.

Differentiation of Acerpseudoplatanus L. cells into tracheary elements (TE) and an increase in the number of TE inHaplopappus gracilis (Nutt.) A. Gray calli were observed after pulse-treatment of the cultures grown in glass tubes with indole-3-acetic acid (IAA) solutions. The effect was enhanced if the treatment was repeated in three subsequent days. The manner of IAA application which caused a wave-like pattern of IAA flow through the callus culture appeared to be more important than the IAA concentration. Induction of differentiation of A.pseudoplatanus cells and an increase in the number of TE inH. gracilis callus did not occur when the calli were grown on agar media supplemented with increased concentrations of IAA.

Ultrastructure of chloroplasts in leaf mesophyll cells of triazine resistant and triazine sensitiveAmaranthus retroflexus L. plants was evaluated stereologically. The most striking difference between both types of the chloroplasts was a small volume of starch inclusions in triazine resistant plants.

Agrobacterium tumefaciens binary vectors carrying kanamycin resistance gene and either C58 T-DNA gene 4 for cytokinin synthesis or genes 1 and 2 for auxin synthesis were constructed and used for transformation of a short-day tobacco Maryland Mammoth. Kanamycin resistant plants were regenerated from a small fraction of transformed tissue and the presence of T-DNA in their genome was verified by Southern blotting. The level of endogenous cytokinin in plants transgenic for gene 4 and the level of endogenous IAA in those transgenic for genes 1 and 2 increased by more than 100 %. A number of morphological characteristics distinguish them from untransformed controls.