Water-stress for 10d at different developmental stages, affected relative water content and leaf water potential of plants. Subsequent rewatering removed these effects. Water stress lowered the contents of chlorophyll, protein, RNA and the activity of catalase, while it increased free proline accumulation and activities of protease, RNase and peroxidase. An overall improvement in biochemical parameters was achieved as soon as the stress was withdrawn by watering and this was reflected in subsequent developmental stages. Water-stress at the reproductive stages induced similar changes as in the vegetative stage but the removal of stress could not improve these parameters to the same extent as at the vegetative stage. In consequence, stress applied at the vegetative stage augmented yield parameters but when applied at the reproductive stage it significantly reduced the yield.

Influence of high intensive flashes on the yield of free radicals in intact seeds and excised embryonic axis, endosperm, and seed coat, and its resulting effect on seedling growth, total biomass production and phosphorus metabolism in wheat (Triticum aeativum), vetch (Vicia sativa L.) and onion (Allium cepa L.) was studied. Free radicals (f.r.) were formed mainly in seed coat and not in the endosperm. Vetch seeds after irradiation had 20.76 X 10¹³ f.r. g^-1 dry intact seed and 17.30 X 10¹³ f.r. g^-1 dry seed coat. Excised seed coats exposed to irradiation also yielded 17.28 × 10¹³ f.r. g^-1 dry matter. High irradiance "white light" flashes induced more f.r. than a monochromatic one of the same photon content. Red (650 nm), farred (750 nm) and even infra-red (1100 nm) radiation did not initiated f.r. formation but resulted in their decay in samples irradiated earlier by "white", blue and green parts of the spectrum. Blue irradiation of seeds led to the decrease in the length of shoots and roots in comparison to "white", green and red irradiation but their biomass increased faster than in the seedlings obtained from non-irradiated or irradiated with "white" and green radiation. The quantity of total acid soluble phosphorus followed a sequence with respect to wavelength of radiation: 436 nm > 650 nm> > 540 nm > non-irradiated > 300-800 nm. Quantity of inorganic phosphorus remained unaffected by different spectral character of radiation. The quantity of organic acid soluble nucleic phosphorus and acid insoluble polyphosphates was higher in samples irradiated with red beams (650 ± 6 nm).

There was a slow and gradual rise in the deoxyribonucleolytic activity of both excised and attached first leaf of ragi (Eleusine coracana Gaertn. cv. PR 202) during senescence. The decline in DNA content is correlated with the rise in deoxyribonucleolytic activity; but both DNA and deoxyribonucleolytic enzyme were photo-insensitive and did not respond to the application of senescence retardants - benzimidazole and gibberellic acid. Increase in deoxyribonucleolytic activity in excised leaves was not affected by actinomycin D; it was, however, wholly or partially prevented by cycloheximide. The effect of the translation inhibitor depended on the time of application. The enzyme activity seems to have no specific relation with the process of senescence.

The contents of reducing sugars, proteins and ascorbic acid and the activities of protease, peroxidase, catalase, indole acetic acid oxidase, ascorbic acid oxidase, succinic dehydrogenase and the rate of respiration were investigated in regenerating and non-regenerating parts ofClerodendrum viscosum Vent. root cuttings. All the above variables have registered higher in the regenerating parts, particularly at the distal end where roots appear, than in the non-regenerating parts of root cuttings. The contents of metabolites and the activities of enzymes in the presence of endogenous cytokinins at the proximal end and auxins at the distal end, were compared and discussed in relation to the initiation of shoots and roots at two ends of root cuttings. In general it was concluded that interacting hormonal and nutritional factors must be appropriate to initiate shoots or roots in the root cuttings.

Contents of individual carotenoids in the fruits of Ramillete cultivar ofCapsicum annuum L. changed during ripening of recently harvested fruits or fruits stored 15 d in a dark and cool room. β-carotene and β-cryptoxanthin contents rose to a maximum and then declined, while the contents of other earotenoids rose to a rather steady level. Capsanthin was the main carotenoid which together with capsorubin were responsihle for the ripening colour.

A linear relationship was obtained between the logarithm of count rate and absorber's (Aluminum foil and leaf) effective thickness in the range of 4.25 to 18.00 mg cm^-2. Also relative water content (RWC) and absorber effective thickness was linearly related (Y = -89.80 + + 15.84 X, and r = 0.99). From these relationships it was possible to determine the RWC of a rice leaf simply by measuring the radiation intensity of fresh, fully turgid and completely dry leaf by beta ray gauge technique without the added necessity of determining the mass of the leaf.

The sensitivity of stomata to water stress increased during ontogeny of primary bean leaves growing under constant environmental conditions: the decrease in both adaxial and abaxial epidermal conductances was induced by slightly more negative values of leaf water potential in young than in mature and especially old leaves. However, these differences were less expressive than the differences mentioned in the literature for leaves of different insertion level, where adaptations to microclimatic conditions in different canopy layers in addition to ontogeny may occur.

During high altitude acclimatization the highest number of amino acids were found in temperateArtemisia species (A. vestita) and the lowest one in tropical species (A. scoparia). The amount of free amino acids in temperateArtemisia species was higher when this was grown at 3600 m altitude. InA. scoparia, A. vulnaris andA. parviflora, the higher amount of individual amino acids was ascertained in plants grown at lower altitudes.
InA. vestita, the nitrogen contents per unit dry matter was lower in plants grown at high altitude. In the other three species, the contents were significantly higher in the leaves of plants grown at a higher altitude. The nitrogen contents per unit leaf dry matter determined during active growth of plants were minimum inA. parviflora and maximum inA. vestita. With progressing plant senescence the concentration of nitrogen decreased in all species studied.

Sugar-beet invertase preparation was found to be highly temperature-dependent in its activity (T_opt = 40 °C), to be decreased by bivalent metal salts (especially CaCl₂ and MgCl₂ and relatively unaffected by heavy metal cations from the end of the periodic table. Inhibitors of SH groups, such as iodoacetamide andp-chloromercuribenzoate, were highly inhibitory while ouabain was a medium-strength inhibitor, with 2,4-dinitrophenol having no effect. The intracellular pH of 7.3, corresponding to the optimum for invertase (at 7.2) could be substantially decreased (to 5.8) by exposure of cells of whole sugar-beet roots to carbon dioxide in aqueous solution.

Long-term effects of glycinebetaine on water use efficiency (WUE), dry matter production and net photosynthetic rate have been studied. Applied glycinebetaine enhanced the WUE and the grain yield of wheat.

The rates of maintenance and growth components of leaf dark respiration of a C₃ plant (Phaseolus vulgaris L.) and C₄ plant (Zea mays L.) as affected by temperature were studied using the McCree concept. Respiration rates were measured by means of infrared gas analysis in a closed gas exchange system. In both C₃ and C₄ species R_D and R_m increased with temperature in the temperature range (15-62 °C) studied. R_G depended on temperature with an optimum near the temperature optimum of gross photosynthetic rate, P_g. Significant correlation between R_D and R_M and between R_G and P_G was found.

Water relations of plant cenopopulations of understorey species (7 herbaceous perennials, 1 shrub, and 1 tree seedling) growing in an oak-hornbeam forest in SW. Slovakia is markedly influenced by natural sunflecks moving on the forest floor, where stomatal conductance and transpiration rate are significantly higher than in shade areas. In the course of a day, the leaf stomatal conductance fluctuates, following irradiance of the leaf, from minimum in full shade to maximum in sunflecks, including intermediate values in transient conditions. Therefore, there is also a large variability in water saturation deficit and transpiration rate within the cenopopulations of the understorey species. These variations should be considered in modelling the physiology of woodland understorey species.

Regeneration of complete plants is possible from free-cell derived colonies ofIndigofera enneaphylla. In addition to factors such as plating density and composition of the nutrient medium, carbon dioxide is essential for the growth of free-cells whereas changing the light intensity had no effect. Cell colonies were obtained at a plating density of 2.5 × 10³ cells/ml on medium containing benzylaminopurine, 2,4-dichlorophenoxyacetic acid and casein hydrolysate and plantlets were obtained on medium containing only BAP.

In rice (Oryza saliva L. ev. Java), the first (younger) leaf senesced later than the second (older) leaf as shown by the decline in chlorophyll and protein contents. Kinetin treatment significantly retarded senescence of leaves, while abscisic acid (ABA) treatment promoted it. The second leaf exported more³²P to the newly emerged growing leaf at the early stages than the first leaf, which always showed higher retention of³²P than the second one. Kinetin treatment lengthened the duration of³²P export and also increased the retention capacity of both leaves, while ABA had the opposite effect. The second leaf showed a higher depletion of nitrogen and phosphorus but à lower depletion of potassium than the first leaf. Kinetin treatment retarded the decline in nutrient content (N and P) while ABA treatment hastened it. Neither growth substance had any effect on potassium content. The content(s) of endogenous eytokinin-like substance(s) decreased while ABA-like substance(s) increased in the two leaves with senescence: these changes in the second leaf took place earlier than in the first leaf.

The mode of transport and regulative properties of phenylacetic acid (PAA) were studied in 11-cm long segments of pea epicotyls capable of growth. The transport of PAA m both the basipetal and aeropetal direction was limited to tissues situated immediately below and/or above the site of its application. PAA was able to promote the flow of¹⁴C-ABA in the acropetal direction. PAA-initiated thickening growth was probably the cause of this promotion.

Data point fields of values of the dependence of nitrogen and potassium concentration in shoot dry matter on dry matter weight in the course of the vegetation cycle at four stages of development of spring barley (Hordeum vulgare L. cv. Ametyst) plants were derived from a four-year-cycle of stationary field nutrition experiments at two localities. Three selection procedures of the boundary data are described. Graphical outputs and their subsequent mathematical expression enable an objective construction of regressive upper and lower boundary curves of the data point fields. The shape of the curves is characteristic of each investigated element. The position of the upper boundary curve can characterize the maximum uptake ability, that of the lower curve the maximum efficiency of utilization of absorbed nutrients, and their amplitude the requirement extent of the species or cultivar investigated. The boundary curves can be objectively constructed for individual nutrients from a sufficiently vast set of data from a very broad spectrum of ecological conditions (for example from stationary field nutrition experiments at various localities).

Mustard (Brassica juncea) Coss., chickpea (Cicer arietinum L. and barley (Hordeum vulgare) L. were grown under different moisture levels. Diurnal changes in leaf water potential showed lower values and higher fluctuation in mustard, chickpea and barley grown with no irrigation as compared to one supplemental irrigation. Diurnal maximum of adaxial stomatal conductance in mustard and barley was higher under one irrigation treatment. In mustard stomatal conductance of abaxial surface of leaf remained higher than adaxial surface of leaf throughout the day, whereas the reverse was true in barley. Also the leaf and soil temperature and reflectance were slightly higher in all the three crops under no irrigation.

Neutral proteinase was found in the leaves ofRicinus communie as assayed with α-casein and H-D-Val-Leu-Lys-pNA as substrates. The enzyme is maximally active at pH around 7.4. A selective adsorbent for serine proteinase was prepared by attaching aprotinin to aminoalkyl-porous glass.
When partially purified leaf proteinase was passed through a column containing this adsorbent, the proteinase activity present was bound to the porous glass. The proteinase eluted at IM NaCl was inhibited by aprotinin, leupeptin, DFP, phenylmethylsulfonyl fluoride (PMSF) and serine proteinase inhibitor fromR, communis leaves, whereas pepstatin, EDTA, EGTA, and DTT had no effect on the enzyme. This inhibition profile suggests the leaf proteinase is a neutral proteinase, such as a serine proteinase.

Young seedlings ofGmelina arborea Roxb. were subjected to 2 weeks of drought. Despite the gradual reduction in stomatal conductance, leaf and root growth was not affected until the later part of the stress period. This was attributed to solute adjustment in the roots of the plants. As the severity of water stress increased, root growth was prolific in all the soil segments. As a result, water in the lowest soil segment was used to maintain plant turgor, which in turn sustains the leaf and root growth during the water-stress treatment. The influence of soil water content and soil water potential upon soil water uptake rate was also evaluated on soil profile basis. Rates of extraction began to decline in all soil segments as soon as soil water potential fell below -0.06 MPa, presumably as a result of vapour gaps between the root and soil (root: soil interface resistance). It is suggested that the growth of roots ofGmelina plants away from drying soil will minimize the resistance to water uptake.

Some of the effects of oxygen concentration in the external medium bathing castor bean cotyledons were investigated.
At 700 μM O₂, the sucrose-dependent proton influx was dependent on external pH while sucrose influx was independent of pH between 4,5 and 6; proton influx and sucrose influx were both dependent on external sucrose concentration; both were saturated above 50 mM sucrose. The stoichiometry H+/S decreased with increasing pH and sucrose concentration. These data were consistent with the results obtained in stirred or aerated external medium.
Oxygen consumption, acidification of the medium, sucrose-dependent proton influx and sucrose uptake increased with increasing oxygen concentration up to 700 μM where saturation was reached. Bubbling with air (O₂, 160 μM) resulted in the same increase despite lower oxygen concentration. It is suggested that not only O₂ concentration but also CO₂ concentration act on O₂ consumption, and proton and sucrose fluxes.

The effect of derivatives of benzoic and cinnamic acids, quereetin,p-benzoquinone, and 2,5-dimethylbenzoquinone on oxygen consumption mitoehondrial suspensions and on the activity of some respiratory chain enzymes was studied. Benzoquinone and 2,5-dimethylbenzoquinone highly significantly inhibited the respiration and phosphorylation rates and malate- and succinate dehydrogenase activities. Chlorogenic acid, similarly as the quinones, very significantly inhibited the activities of the studied dehydrogenases but did not affect cytochrome oxidase. Oxygen consumption by intact mitochondria was not inhibited, only the oxidativo phosphorylation was significantly uncoupled. Quereetin significantly enhanced dehydrogenase activities and completely inhibited cytochrome oxidase activity. The respiration and phosphorylation activities of the mitochondria were significantly inhibited by quereetin. The effect of the other phenolic compounds studied on respiration and phosphorylation activities was not significant. Succinate dehydrogenase activity was the most affected enzyme among the respiratory chain enzymes. It was significantly inhibited by all the above phenolic compounds at 1^-4M or 5 10^-5M concentrations with the exception of gallic acid.

Protease activity inSpinacia oleracea leaves, but not roots, increased when sodium sulfite, hydrogen peroxide and sodium azide, but not sulfuric acid, were injected through the petiole under light conditions. On the other hand, protease inhibitory activity in both the leaves and roots decreased by the injection.
Protease activity inRicinus communis leaves increased when hydrogen peroxide and sodium sulfite were injected through the petiole and kept for 4 h under light conditions. No visible injuries were caused to the leaf. On the other hand, protease inhibitory activity in leaves decreased by the injection of hydrogen peroxide.
Changes in the activity of protease caused the senescence of leaves such as chlorosis and necrosis which were observed with leaves injected with hydrogen peroxide after one week. These results suggested that in the healthy leaf, the protease inhibitor protects the cellular components from the protease.