With increasing altitude, the concentrations of chlorophyll (chl), carotenoids and phenolics decreased but the chla :b ratio increased in the fourArtemisia species grown at four altitudes. The increase in chla : b ratio was due to a reduction in chlb content. The changes in anthocyanin content were irregular. Thus phenolics and anthocyanin pools may be differently regulated along an altitudinal gradient.

The effect of phosphorus deficiency on the activity of acid phosphatase of the first, second and third leaves of maize plants was followed. The supernatant obtained by centrifuging the homogenate of plant tissue at 1500 ×g was further centrifuged at 18 000 ×g, the sediment marked as fraction II and the supernatant as fraction III. Acid phosphatase activity of fraction II of the first to third leaves was for the whole period of culture higher in plants grown in the nutrient solution without phosphate. In fraction III this relation was established in the first leaf, after 3 days of culture in the second leaf and after 5 days in the third leaf. In all leaves higher enzyme activity was unambiguously determined in fraction III when compared with fraction II. Higher acid phosphatase activity was established in those leaves which were younger in their development, particularly in the first days of culture. With the ageing of leaves the enzyme activity decreased.

2-chloroethylphosphonic acid, unlike chlorocholinechloride, does not suppress gibberellin biosynthesis inGibberella fujikuroi cultures, and nullifies the effect of applied gibberellin A₃ on wheat seedling growth.

The mechanisms by which exogenously applied plant growth regulators act to express those genes that are selectively involved in cell and tissue differentiation are not at all well comprehended. However, the ontogenetic sequences of events that enable receptor or target cells to be activated and to undergo dedifferentiation and redifferentiation, can often be followed experimentally and can lead to a better understanding of the causal relations and control mechanisms in coordinated cell growth and development.
Cytokinins, applied either in an agar medium or as high-concentration, short-duration pulses to expiants or as high-concentration, intermittent sprays to intact plants, induce switches in the normal developmental pattern of cells of certain explanted tissues. Examples of cells that are particularly receptive are the subsidiary cells of stomatal complexes and the differentiating cells of very young presumptive leaf primordia, that is before the latter have become irreversibly determined as leaves.

The mobilization of protein nitrogen reserves in apple shoot bark is subject to abscisic acid (ABA)-mediated regulation. At the biochemical level proteolytic activities in the shoot bark are suppressed in the autumn. As endogenous ABA levels decline during the autumn and winter tissue protease levels increase in parallel with the rate of inducible breakdown of reserve protein; metabolic demandper se plays no significant role. This process is used as a model system to explore the possibilities for chemical regulation ("bioregulation") of ABA-determined dormancy phenomena by: manipulation of tissue ABA concentrations, substitution of synthetic growth regulators and direct interference at the site of action.

Two photooxidation products of indol-3-ylacetic acid (IAA), 3-hydroxymethyl oxindole (HMO) and 3-methylene oxindole (Meox) were almost as effective as IAA in stimulation of growth of oat (Avena saliva cv. Kent) coleoptile sections. The IAA failed to give stimulation of growth after pretreatment of the coleoptiles with chemicals inhibiting oxidation of IAA, but the growth promoting effects of HMO or Meox remained unaffected by such pretreatment. After pretreatment with the chemicals which can form an adduct with Meox, the growth promoting activities of IAA, HMO or Meox were lost showing the involvement of the oxindole pathway of IAA metabolism in IAA action. Time-course experiments also showed that the stimulatory effects of HMO and Meox were the same as IAA.

Acid-soluble phosphate esters were determined in extracts of plant material after a 24 h exposure of the roots of intact alfalfa plants to nutrient media labelled with³²P_i. Similar phosphate ester patterns were found in 2-, 3-, 8-, and 9-week-old plants with the exception of Gra-P which could be detected only in shoot extracts. However, phosphate ester levels differed in the shoots and roots. Whereas Fru-P₂, Glc-6-P, Fru-6-P, and adenine nucleotides were more abundant in the shoots, Grn-P and P-choline levels were higher in the roots. Certain differences in the levels of P-esters were also recorded between plants susceptible and resistant to bacterial wilt.

Abscisic acid, a potent growth inhibitor inhibits hypocotyl growth ofRaphanus sativus seedlings. Phenolic compounds,viz., trans-cinnamic acid, chlorogenic acid, ferulic acid, salicylic acid, tannic acid and quercetin when applied with ABA, antagonize ABA action and restore normal seedling growth.
Gibberellic acid promotes hypocotyl growth and on combined application with ABA, the ratio of their concentrations determines the course of the resultant growth. This interaction can be modulated by phenolic compounds. Phenolic compounds in low concentrations when present together with GA and ABA, favour GA-induced growth by antagonizing the inhibitory influence of ABA.
The inhibitory action of abscisic acid on a wide range of growth processes is so far known to be reversed only by growth promoting hormones,viz., IAA, GA and cytokinins. Antagonistic action of phenolic compounds towards ABA, and increasing the action of GA when present together with GA and ABA, establishes a dual role to this class of compounds; balancing the effect of both growth promoting and growth inhibiting hormones.

The contents of NADP⁺, NADPH, changes in the activity of glucose-6-phosphate dehydrogenase and some questions relating to its regulation in leaf tissues of tobacco plants infected with PVY were studied. The content of NADP⁺ and the total sum of pyridine nucleotides decreased after inoculation to 15 % and 30 %, respectively, whereas the content of NADPH increased up to the threefold control value. The contents of NADP⁺, NADPH and Σ(NADPH + NADP⁺) linearly correlated with the reproduction curve of PVY. The value of the reduction charge RC and the value of the ratio NADPH/NADP⁺ sharply increased after inoculation up to tenfold and eighteenfold values, respectively, of the healthy control.
The activity of glucose-6-phosphate dehydrogenase was markedly increased in virus-infected tissues during the entire experimental period both in crude homogenate and after its partial purification when compared with the values found in healthy control plants. The time courses of the activity curves of both crude and partially purified enzymes were coincident and correlated with the reproduction curve of PVY. The results indicate the involvement of coarse regulation of the activity of the enzyme by its content without the involvement of fine regulation by the ratio NADPH/NADP⁺ and RC.

Gibberellins A₃ and A₁₃ cause floral induction inImpatiens balsamina, a qualitative short day plant, under non-inductive 24-h photoperiods (continuous illumination). However, the influence of the two inductive factors,i.e. gibberellins and short days (8-h photoperiods) on the peroxidase enzyme system is different. The total peroxidase activity decreases under both inductive and non-inductive photoperiods, with or without gibberellin treatment. The electrophoretic pattern of isoperoxidases changes only in response to gibberellin treatment. Under 24-h photoperiods, treatment with gibberellins A₃ and A₁₃ causes the appearance in the stem of three additional isoenzymes of peroxidase (Rm 0.50, 0.71 and 0.76). These bands do not appear in the leaves, which are non-essential for gibberellin-caused floral induction in this plant. Under 8-h photoperiods also, gibberellins induce the appearance of new isoenzyme bandsi.e. two in the stem (Rm 0.50 and 0.76) and one in the leaves (Rm 0.05). These may be correlated with the synergistic increase in the number of floral buds in these plants in response to simultaneous exposure to two inductive factors.

A binary vector system inA. tumefaciens for the introduction of foreign genes into the plant genome was developed. The first component is the Ri plasmid and the second component is a small vector plasmid, replicating inAgrobacterium, which carries the 25 bp terminal sequence of the Ti plasmid, theNos gene as the selectable marker and neighbouring sequences of the Ti plasmid. Functions necessary for integration are providedin trans by the virulence region of the Ri plasmid. Transformed cells are selected on the basis of hairy root tumor proliferation and agropine synthesis. They also showNos activity coded by the gene on the small part of Ti T-DNA.

On the basis of proportionality between flow and its conjugated force a mathematical model for volume, current and osmotic flows was designed and a method for the experimental measurement of flows, the transbarrier (trans-segmental) potential and the rate of flow was devised.
The results obtained experimentally as well as using the mathematical model indicate that the plant root is differentiated not only according to localization, but also according to the conductivity, permeability and selectivity of these tissues.

XAD-4 resin was used to isolate cytokinins present in Baltic sea water. Four compounds were tentatively identified as 6-(3-methylbut-2-enylamino) purine and zeatin, and their ribosides.

The protoplasts of the moss Anoectangium thomsonii, isolated from protonemal cells underwent divisions in 48-72 hours on modified MS medium enriched with growth regulators, 2,4-D and kinetin, 10 % sucrose and coconut water (5 %). Subculture of protoplast derived cells in a medium of relatively low osmotic potential (5 % sucrose) produced dark green calli which could be maintained completely undifferentiated.

Certain cultivars ofMalus growing at Geneva, New York, USA, begin growth and bloom 2 -3 weeks later than commercial cultivars of apple. Our research suggests that these late bloomers bloom late because they have a very high chilling requirement for bud burst. The chilling requirement interacts with the heat requirement for bud burst in such a way as to result in delayed bud burst and bloom. Abscisic acid (ABA) decreases in the terminal buds of both early and late bloomers during the chilling period, but it decreases more rapidly in the early bloomers. It has not been determined if ABA plays a role in controlling bloom date.

Glass microelectrodes filled with antimony were constructed, the electrical potential of which linearly depends on pH and is not influenced by light. Recording at the surface and in the cytosol (the latter corrected for the transient response of the membrane potential measured with a conventional electrode) showed both intra- and extracellular alkalization brought about by irradiating the algaPithophora pragensis. DIURON (DCMU, 3-(3,4-dichlorophenyl)-1,1-dimethylurea) in the concentration 10^-4M almost entirely abolished the photoeffect.

Virus particles of isometric shape with a diameter of 26 nm were found in the sieve tubes and accompanying phloem cells in ultrathin sections prepared from the nerves of white mustard (Sinapis alba L.) leaves and roots infected with the beet mild yellowing virus (BMYV). BMYV particles were much more frequent in the roots ofSinapis alba plants. Isometric particles were not found in the leaves and roots of healthy mustard plants.

The content of ATP, ADP, AMP, P_i, the activity of the enzymes involved in the glycolytic pathway, some problems of their regulation by adenine nucleotides and some basic problems connected with tissue energy balance were studied in tobacco plants infected with the potato virus Y (PVY). The contents of ATP and ΣAdN were increased in virus-infected tissues when compared with healthy tissues and correlated with the PVY reproduction curve. ADP and AMP contents decreased just after the inoculation and increased at the end of the experimental period, P_i content was not influenced by the infection.
The activities of the key enzymes of the glycolytic pathway (6-phosphofructokinase, hexosediphosphatase, and pyruvate kinase), determined both in crude homogenates and after partial purification, did not differ during the entire experimental period from the values found in healthy control tissues, similarly as the activities of glucosephosphate isomerase, glyceraldehydephosphate dehydrogenase, phosphoglyceromutase and enolase observed in crude homogenates. The unchanging AEC value in virus-infected tissues simultaneously indicated that no change in the rate of the glycolytic pathway occurred even under "invivo" conditions at the period of the acute stage of infection.