The absorptivity of the leaves at all the wavelengths decreased whereas the reflectivity and transmissivity increased when an alpine perennial herb, Selinum vaginatum was grown at lower (550 m) elevation. The lower elevation climate modified leaves to absorb comparatively less near-infrared radiation as compared to that under natural habitat. The lower altitude habitat had a positive effect on infinite reflectance and a negative effect on absorption and scattering coefficients of the leaves. Based on the scattering and absorption coefficients for upper and lower leaf surfaces, the 'sieve' and 'detour' effect factors were estimated. These factors indicate that while 'sieve-effect' increases the 'detour-effect' decreases when this plant is grown at lower elevation. This explains lower light absorption (PAR) in this plant when grown at lower elevation. For survival under the habitat with high thermal load the leaves of this alpine herb could maintain lower temperature by way of reduced absorption in near-infrared radiation region which probably is accomplished by lower water contents and thickness of leaves at lower elevation.

The cotyledons of yellow lupin seeds contain 15.4 mg of the albumins, water soluble proteins, per 100 mg of dry matter. These proteins were resolved by SDS gel electrophoresis into 13 polypeptides with relative molecular mass, Mr, between 16 000 and 84 000. Isoelectrofocusing analyses of the albumins showed that they were composed of six components with isoelectric points between 4.1 and 5.5. These results have indicated that the albumins are acid proteins and exhibited molecular and charge heterogeneity.

The glycollate metabolism of wheat (Triticum vulgare Vill. cv. Sonalika) and rice (Oryza sativa L. ev. Jaya) leaves was studied during senescence by estimating the endogenous levels of glycollate and hydrogen peroxide (H₂O₂) and the activities of glycollate oxidase and catalase. In comparison with light incubation the incubation of excised leaves in the dark caused a decline in the glycollate content and in the activities of glycollate oxidase and catalase, and an increase in the H₂O₂ content, more marked in the leaves of rice than in the leaves of wheat. Glycollate oxidase activity gradually decreased with incubation time, and glycollate metabolism decreased during senescence. The glycollate oxidase in particular and glycollate metabolism of rice were more sensitive to incubation time than those of wheat. Kinetin increased the glycollate oxidase activity and glycollate metabolism during senescence, while ethrel (2-chloroethylpho-sphonic acid) and ABA (abscisic acid) reduced these activities in both plant species.

Wolffia arrhiza (L.) Wimm. was grown axenically in the chemostat under white luminescent light (photon fluence rate 23 ujnol m^-2 s^-1) and phosphate or magnesium limitation (0.075 and 0.01 jxmol 1^-1, respectively). Aliquots (1 g fresh mass) were taken from the continuous cultures and were irradiated for 1 h with either white light (control) or monochromatic blue (453 nm) or red (654 nm) light. The amount of [5^-3H]-uridine incorporated into cytosolic and chloroplastic rRNAs during these exposures was estimated and following results were obtained: In phosphate limited plants rod light considerably reduced and blue light slightly increased label incorporation as compared with the control. Moreover, in red light, chloroplast incorporation is relatively more slowed down than that in the cytosolic compartment (34 % as compared to 59 % of the control). In blue light the enhancement is approximately equal in both compartments. In magnesium limited plants incorporation under both blue and red light is moderately slower as compared with the control. In both cases also the retardation is slightly greater in the chloroplast than in the cytoplasm. The results suggest that rRNA metabolism is controlled by light quality as well as by mineral nutrition.

Ten centimeter long stem cuttings of sweet potato (Ipomoea batatas L. cv. Georgia Jet) with intact apex and leaves were cultured in distilled water as well as in varying concentrations of abscisic acid (ABA) in open top chambers at 364, 438 and 666 cm³ m{-3}CO₂. Low concentration of ABA promoted rooting and elongation of roots at 364 cm₃ m{-3} CO₂ while rooting was suppressed at enriched levels of CO₂. However, biomass production in shoots and roots was higher in 666 than in 364 cm³ m^-3 CO₂.

In the roots of 4-day-old pea plants germinated in unsterile soil from Rhizobium-inoculated seeds, a higher level of native IAA was determined than in roots of pea plants germinated in sterile soil from superficially sterilized seeds. The IAA level in plants grown from inoculated seeds increased markedly up to the age of 6 days of the plant, while in plants growing under sterile conditions it did not significantly change during the same period. Between the 6th and 10th days of the age of the plant, a decline in the IAA level was observed in roots of plante growing from inoculated seeds. It was not until after 10 days of age of the plant that the level of IAA in nodulated roots again increased.

An enzyme extract from apple(Pyrus malus Borb.) seeds which causes the disappearance of free indol-3-ylacetic acid (IAA) requires the presence of oxygen, but is not inhibited by cyanide. Using 1-¹⁴C-IAA it has been demonstrated that the IAA transformation is not accompanied by its decarboxylation. Decarboxylating IAA oxidase is absent during the whole period of apple seed cold stratification. Free IAA has not been detected in dormant apple seeds and in seeds stratified at low temperature. It appears during stratification at 25 °C. Ethyl ester of IAA and indol-3-ylacetyl aspartate have been identified in dormant and after-ripened seeds. Exogenous 1-¹⁴C IAA taken up by apple embryos is converted into conjugates with aspartate and short peptides containing an aspartate moiety.

The free proline and chlorophyll contents, and the chlorophyllase, peroxidase and nitrate-reductase activities were determined in sunflower seedlings grown under controlled conditions and submitted to water stress induced by 14 % polyethyleneglycolj (M_r = 4000) or isotonic NaCl solution. Combined free proline content and peroxidase activity may be used for detection of the factor inducing water stress.

The structure of the cells was studied in two strains of grapevine calli (Vitis riparia ×V. labrusca). These callus cultures contained only highly vacuolised cells. The pattern of division in these slightly cytosolic cells was described. In both callus strains caryological instability has been found.

Seasonal changes in leaf water potential (Φ) and leaf conductance (g₁) were determined in almond trees under different irrigation regimes. The development of water stress in the rainfed treatment induced a specific seasonal dynamics of Φ values and an important reduction in g₁ values. A decrease in g₁ values occurred independently of the irrigation treatment through the growing season. No statistically significant differences were obtained in g₁ values within the drip irrigated treatments.

A histochemical method for the determination of IAA-oxidase has been used in sections of various aerial parts of winter wheat plants. High IAA-oxidase activity was localized in the cell walls of sclerenchyma near the periphery of the stem, in the vascular bundle sheath of sclerenchyma and in xylem, both in the stem and in the leaf. The cell wall-bound IAA-oxidase activity therefore appeared in lignifying tissues. The staining was very weak or absent in the cell walls of parenchyma tissues and phloem. The positive reaction of the cytosol at the bulbous ends of guard cells and in the leaf primordia is presumed to be due to cytosolic IAA-oxidase. These results are discussed in relation to peroxidase localization and to our previousin vitro studies.

Needle primordia were isolated from embryonic shoot expiants of 88 year oldPicea abies (Norway spruce) in order to develop a method for micropropagation using adult mother trees. The isolation of needle primordia in combination with frequent subculture, stimulated the formation of peripheral meristematic tissue in expiants cultured on a modified Murashige & Skoog medium supplemented with cytokinin. Transfer of isolated needle primordia with peripheral meristematic tissue to medium without growth regulators, and with a reduced ratio of NH+4/ NO-3, resulted in the formation of adventitious buds.

Daughter cells of the chlorococcal algaScenedesmus quadricauda were incubated under photosynthesizing conditions in a sulphur-free medium. The course of the cell cycle under these conditions was changed in daughter cells which differed in their stage of development. In absence of sulphur, advanced daughter cells with two nuclei and 2 or 4 genomes passed a cycle identical with that of control in sulphur containing medium. Each cell yielded eight binuclear daughter cells. With less advanced daughter cells (one nucleus and 1 or 2 genomes) restriction of RNA synthesis occurred near to the end of the cell cycle and protein synthesis ceased two hours later (practically at the time of the protoplast fission). The last round of DNA replication found in the control culture was not initiated in sulphur-starved culture and uninuclear daughter cells with one genome were released.
If the daughter cells coming from the starved populations were kept further in the sulphur-free medium, macromolecular syntheses were dramatically restricted. Only photosynthesis continued to produce starch at a similar rate as in normally grown cells. Thus, a very large amount of starch accumulated. Supported by these reserves, starved cells refed with sulphur passed an entire cell cycle in the dark and divided into eight daughter cells. In sulphur-supplied cells, both in the dark and in light, RNA, protein and DNA synthesis started without any delay in a similar way as in the control culture. Competition for sulphur reserves occurred between the growth and division processes; the former were preferred in the light and the latter in the dark.

Genotypes of mustard (B. juncea) were evaluated for concurrent changes in leaf water potential (Ψ), leaf osmotic potential (π), leaf turgor potential (P) and leaf relative water content (RWC) during moisture stress at reproductive stage of growth. The slope 'b' in the regression between Ψ and π varied from 0.43 to 0.97 and was positively correlated with P and RWC. The genotypes with 'b' around 0.7 were able to maintain P of about 0.5 MPa at Ψ of - 2.5 MPa and thus such value of 'b' seems to provide enough degree of tolerance against drought.

Growth and ionic relations were studied in six triticale cultivars of different geographical origins grown in a greenhouse in nutrient solution with or without the addition of 100 mM NaCl. In 21 d old plants of all the six cultivars growth was little affected in the salt treatment, whereas in the subsequent three harvests during vegetative phase (after 31, 38 and 45 d), growth reduction effects of salinity were progressively pronounced. Generally, shoots of all the six cultivars accumulated relatively more K+ as compared to Na+ or Cl-. Differential accumulation of K+, Na+ and Cl- by various cultivars was coupled with variable rates of Na+ and Cl- transport from root to shoot which were - to some extent- related to cultivar differences in growth in saline root media. Chloride content of shoots of the six cultivars was negatively correlated with the relative growth reduction due to salinity at the four harvests.

All the concentrations (25-150 mgl-¹) of the phytohormones kinetin, IAA (indol-3-ylacetic acid) and GA₃ (gibberellic acid) increased the activity of DCPIP (2,6 dichlorophenolindophenol)-Hill reaction, chlorophyll and protein contents over the control data in leaves ofSechium edule Sw. on Darjeeling hill of the Eastern Himalayas; while ethrel (2-chloroethylphosphonic acid) treatments decreased these parameters in the hilly species. The most effective concentrations in increasing these parameters were 50 mg 1-¹ of kinetin, 50 mg 1-¹ of IAA and 100 mg 1-¹ of GA₃; whereas 50 mg 1-¹ of ethrel was most effective in decreasing these parameters during the induction of senescence in the hilly vegetable crop. The increase in these parameters was greatest with kinetin, followed by IAA and least with GA₃ in the hilly plant species studied.

Eight to nine months old seedlings of the Cactaceae Gereus validus HAWORTH grown in soil culture were chosen to study day-night cycles of net CO₂ exchange, indicating the stomatal rhythm of crassulacean acid metabolism, CAM, in relation to day-night changes of abscisic-acid levels. Drought stress was imposed by repotting the seedlings in dry sand and keeping them without watering for up to 37-39 days while control plants were watered regularly. Abscisicacid levels were higher in the stressed plants than in the controls and higher in the light period aa compared to the dark period. In the stressed plants abscisic-acid levels increased throughout the light period. Abscisic acid reached particularly high levels in the late afternoon in plants stressed for 37 days. It is conceivable that stomatal closure during the first part of the light period of CAM is elicited by high internal partial pressures of CO₂ built up by decarboxylation of nocturnally stored malic acid. However, the elimination of late-afternoon stomatal opening and the reduction of stomatal opening during the dark period of CAM observed under conditions of drought stress must have other reasons. The analyses of abscisic acid presented allow the conclusion that this stress hormone is involved in stomatal regulation of CAM under such conditions.

The size of the spring barley root system was studied on the basis of its electric capacity in plants grown in nutrient solutions either lacking or containing nitrogen in the form of nitrate or ammonium.
Root electric capacity changed in dependence on nutrition from Day 12 after emergence, when F values increased in the root systems of plants exposed to nitrate and ammonium salts. In plants grown in H₂O, the values of electric capacity statistically significantly decreased on Days 15 to 17, in plants grown in PK solution lacking nitrogen on Day 20.
Root electric capacity of plants grown in full nutrient solution gradually increased on Day 18 after emergence. Then a marked increase in root electric capacity values followed with no statistically significant differences between NH₄ ⁺ and NO₃ ^- nutrition. Nitrate nutrition of barley plants only resulted in an increased root to shoot mass ratio.

Physiological regions of yam tubers were morphologically defined in different specie into 'Head', 'Middle' and 'Tail', while the limits of these regions were studied using phosphorylase activity. Variation in enzyme activity, pH and protein concentration was found in different regions of the tubers. Old yam tubers had significantly higher activities of saccharide degrading enzymes, hexokinase, phosphorylase, glucose-6-phosphate dehydrogenase, phosphofructokinase and pyruvate kinase, than the new tubers. However, activity of phosphofructokinase in newD. rotundata was higher than that of old tuber. The high activity of phosphorylase in different regions of all the yam tubers examined indicates a very important role of this enzyme in starch degradation inDioscorea species. The measured pH and protein concentration were also higher in old yam tubers. Except for phosphorylase, these enzymes had alkaline pH optima.

The variations in length and fresh and dry mass of etiolated hypocotyls of lupin during the growth have been studied. The growth exhibited by the different zones delimited along the hypocotyl was dependent on the localization of the zone as well as on the age of seedlings, but in both cases the pattern of growth was similar. During the period of growth studied (seedlings 7 to 21 d old), the growth of hypocotyl was basically due to cell elongation, since the relative elongation of cells was positively correlated with the relative elongation of the hypocotyl.

Both axillary buds belonging to the cotyledons (cotyledonary buds) start to grow on decapitated pea seedlings, but one of them (the dominant shoot) prevails in growth over the other (the inhibited shoot). If the dominant' cotyledonary shoot is removed, the inhibited shoot is released from inhibition and starts to grow. This release from inhibition of the inhibited cotyledonary shoot is accompanied within two hours from the removal of the dominant cotyledonary shoot by a marked increase in the level of endogenous cytokinin-like substances and by a decrease in the level of endogenous IAA. By contrast, a significant increase in IAA level and a decreasing trend in the level of cytokinin-like substances occur in the originally inhibited cotyledonary shoot between hour 4 and hour 48 after the release from inhibition of the inhibited cotyledonary shoot. The level of gibberellin-like substances in the cotyledonary shoot released from inhibition steadily increases from the beginning of the release.

Five independent tobacco regenerant clones obtained after transformation withAgrobdcterium rhizogenes strain TR101 (four clones of the T phenotype, clone 5 a mixture of plants of the T and T' phenotypes) and untransformed plants cultivatedin vitro were gradually acclimated to the atmosphere and transferred to the soil substrate in pots. During 28 d after transplanting the increase of the leaf area was in T phenotype plants greater than in untransformed plants, but 14 d later no significant differences were observed between T phenotype and untransformed plants in leaf area and dry matter. T'phenotype plants, however, had significantly lower values in all growth parameters than T phenotype and control plants. Abaxial net photosynthetic CO₂ uptake (PN) was in both T (clones 1-4) and T' plants significantly lower than that in control and clone 5T plants. Nevertheless, due to the relatively higher adaxial PN in T plants, the total PN through both leaf surfaces was significantly lower only in clone 4 and clone 5' plants. The tendency to higher transpiration rates (E) in clones 1 - 4 in comparison with the control resulted in significant differences in water use efficiency (W.U.E.). Relatively higher E in T plants of clones 1 - 4 was connected most probably with their more developed root system (greater root dry-matter) than in untransformed plants, because no influence of the differences in stornata density on E was found.

High irradiance during treatment of mung bean cuttings favours root formation in response to supplied auxin, whether the latter is IAA or IBA. On the other hand it is inhibitory towards root formation in the absence of supplied auxin. Light promotes the uptake of¹⁴C-IAA into cuttings and its upward movement into the leaves. When¹⁴C-IAA is applied to leaves of cuttings high irradiance favours movement of radioactivity into the epicotyl and hypocotyl. This movement is also enhanced by concomitant supply of IBA to the base of the cuttings. The irradiance under which stock plants are raised also affects the extent of root formation on cuttings. When cuttings are held in darkness without a supply of exogenous auxin they root best if prepared from seedlings raised under high irradiance. However, transport of¹⁴C-IAA out of leaves of cuttings is favoured when cuttings are prepared from seedlings grown under low irradiance. These observations are discussed in relation to auxin transport, photodestruction and, possibly, metabolism.