Effects of Kinetin on the Permeability of Allium cepa Cells

Permeability changes of Allium cepa cells were studied by a plasmometric method. Onion epidermis was floated in phosphate buffer solution with kinetin (2.5 milligrams/liter), or buffer without kinetin as a control, for 10 hours. The treated and control tissues were then transferred to one of the following four permeants: thiourea, urea, maloamide, dimethylurea.     

Reversal of (±) -Abscisin II Induced Inhibition of Lettuce Seed Germination and Seedling Growth by Kinetin

Observations have been made on the effect of synthetic, (±)-abscisin II (dormin), alone and in combination with gibberellin, kinetin and indoleacetic acid, on seed germination and seedling growth of two strains of lettuce, cv. Attraktion and cv. Hohlblättriger Butter. (±)-Abscisin II inhibited seed germination and seedling growth in both strains. The inhibitory effect of abscisin II on seed germination as well as seedling growth was completely overcome by kinetin in both dark and light. Gibberellic acid, on the other hand, proved ineffective in exerting its influence on seed germination in presence of abscisin II but affected subsequent seedling growth as usual. Indoleacetic acid was found to be least potent in reversing abscisin II caused inhibition of seed germination and seedling growtb. It is concluded, that like its effect on certain other naturally occurring inhibitors of seed germination, kinetin can effectively undo the inhibitory effects of abscisin II in these growth processes.     

Specific Effects of Kinetin on the Uptake of Monovalent Cations by Sunflower Cotyledons

Kinetin promoted the uptake of K⁺ and Rb⁺ into detached sunflower cotyledons. This action was concomitant with an acceleration of growth. A slighter promotion of Li⁺ uptake was also noted, but there was no consistent influence on that of Na⁺. A small inhibitory effect on NH₄⁺₄ uptake was apparent when the latter was computed per average weight of sample during the course of incubation. Light also promoted the growth of the cotyledons, but depressed their capacity to absorb potassium. The action of kinetin on cotyledons removed from 5–7 day old seedlings was weaker than on those removed from 2–4 day old seedlings with regard to growth but stronger with regards to K⁺ uptake. When K⁺ uptake by cotyledons taken from 7-day old seedlings was followed with time the kinetin effect was already detectable within a few hours, but it became more pronounced after 10 hours' incubation. Kinetin did not accelerate growth or K⁺ uptake in hypo-cotyl segments. IAA, which was previously shown to promote these processes in hypocotyl segments, inhibited them in cotyledons. A working hypothesis is suggested according to which endogenous auxins and cytokinins regulate the absorption of K⁺ in shoot cells of the intact plant in a manner similar to that in which they act in excised tissues and in this way affect the distribution and redistribution of K⁺ in the shoot; and that they are among the factors which determine the selectivity of ion uptake in the intact plant.     

Effects of applied NaCl on Opuntia humifusa

Plant morphology in the field in Virginia, USA, and growth responses to applied NaCl in a glasshouse were determined for two populations of Opuntia humifusa (Rafinesque) Rafinesque, one from an inland site and the other from the marine strand, which differed in potential exposure to salinity. Cladode dimensions, plant height and rooting depth varied significantly between the populations. Application of NaCl in 50 m M increments up to 400 m M every 3 days for 6 weeks caused the cladodes to decrease up to 30% in thickness, the decrease being about 20% more at 50 to 150 m M NaCl for plants from the inland site than from the marine strand. Inhibition by 150 m M NaCl of the maximum rate of net CO₂ uptake and of the total CO₂ uptake over a 24-h period was greater for the inland population. Growth, especially of roots, was inhibited by applied NaCl, with a decrease in biomass above 200 m M NaCl for plants from the inland site and not until 400 m M for those from the marine strand. Although the root Na⁺ level was the same for plants from the two populations, reaching a maximum of about 8 mg (g dry weight)⁻¹ at 200 m M NaCl, the cladode Na⁺ level was two-fold higher for plants from the marine strand than from the inland site. Thus, exclusion of Na⁺ from the cladodes is not the reason for the greater NaCl tolerance of O. humifusa from the marine strand, which is a habitat that can experience periodic episodes of high salinity.     

Effects of Kinetin and Salinity on Germination of Tomato, Barley and Cotton Seeds

The effects of kinetin and the interaction between kinetin andsalinity on seed germination of three plant species namely Lycopersiconesculentum, Hordeum vulgare and Gossypium hirsutum were studiedKinetin was applied exogenously to the seeds in order to determinewhether this growth-promoting hormone would promote germinationand to see if osmotically-induced dormancy caused by NaCl couldbe alleviated The results indicate that kinetin is capable ofbreaking dormancy in these species and there is a significantinteraction with salinity in tomato and cotton Kinetin, germination, salinity, water stress, salt stress, Lycopersicon esculentum Mill, tomato, Hordeum vulgare L, barley, Gossypium hirsutum L, cotton     

Reversal Effect of Potassium Ion on Microbial Growth Inhibition by Combinations of NaCl,Ethanol and Perillaldehyde

The glutamate racemase (EC 5.1.1.3) gene of a lactic acid bacterium, Pediococcus pentosaceus, was cloned into Escherichia coli C600 with a vector plasmid, pBR322. The requirement of l-glutamate for the growth of E. coli in the minimum medium containing d-glutamate and the formation of a red pigment in a coupled enzyme reaction mixture were used to select clones expressing glutamate racemase activity. Glutamate racemase overproduced as 0.3— 2.0% of the total soluble proteins in a clone carrying the plasmid pICR221, 10.3 kb of DNA, was purified from cell extracts about 130-fold to homogeneity. The purified enzyme has a molecular weight of about 40,000 and is a single polypeptide chain. Glutamate is the sole substrate for the enzyme. Unlike many other amino acid racemases, glutamate racemase is devoid of cofactors: there is no evidence for pyridoxal 5’-phosphate or FAD in the ultraviolet spectrum of the purified enzyme, and the enzyme is not inactivated by carbonyl reagents such as hydroxylamine and sodium borohydride.     

Effects of Kinetin on Transpiration Rate and Abscisic Acid Content of Water Stressed Young Wheat Plants

Effects of kinetin on transpiration rate and abscisic acid content were determined. Leaves from 9-day-old wheat plants (Triticum aestivum L. cv. Weibull's Starke II) were used. —Transpiration rate decreased in excised leaves put in water, but it was maintained at a higher rate when kinetin was supplied. When excised leaves were water stressed by air-drying for 1 h, addition of kinetin resulted in a considerable stimulation of transpiration rate. The effect reached its maximum after 15 h and this level remained relatively unchanged for at least 10 h. Intact seedlings which were stressed before leaf excision, showed only a slight stimulation of kinetin on transpiration rate. — Abscisic acid content slowly increased up to three-fold in 2 days in excised leaves put in water. In excised and water-stressed leaves the abscisic acid content was reduced during the first 24 h and then increased. As the leaves were fully turgid, the increase could not have been caused by water stress. However, both in stressed and unstressed leaves kinetin addition reduced the increase in abscisic acid content. — It is suggested that the stimulation by kinetin on transpiration rate in excised and water stressed leaves was mainly due to the combined effect of (1) a reduction in the activity of endogenous cytokinins, (2) kinetin acting as a ‘substitute’ for the inactivated cytokinins but exerting a stronger effect on transpiration than the endogenous cytokinins, and (3) the ‘extra’ reduction in abscisic acid content caused by the kinetin treatment. Furthermore, the results indicate that changes in cytokinins might be partly responsible for the aftereffect on transpiration.     

Effects of Osmoprotectants upon NaCl Stress in Rice

Plants accumulate a number of osmoprotective substances in response to NaCl stress, one of them being proline (Pro). While characterizing some of the changes in solute accumulation in NaCl-stressed rice (Oryza sativa L.), we identified several other potential osmoprotectants. One such substance, trehalose, begins to accumulate in small amounts in roots after 3 d. We performed a series of experiments to compare the effects of Pro and trehalose on ion accumulation to determine whether the two chemicals protect the same physiological processes. We found that Pro either has no effect or, in some cases, exasperates the effect of NaCl on growth inhibition, chlorophyll loss, and induction of a highly sensitive marker for plant stress, the osmotically regulated salT gene. By contrast, low to moderate concentrations of trehalose reduce Na+ accumulation, salT expression, and growth inhibition. Somewhat higher concentrations (10 mM) prevent NaCl-induced loss of chlorophyll in blades, preserve root integrity, and enhance growth. The results of this study indicate that during osmotic stress trehalose or carbohydrates might be more important for rice than Pro.     

Chloroplasts, Kinetin and Protein Synthesis

The effect of kinetin on protein synthesis of isolated chloroplasts was investigated by following the incorporation of ¹⁴C-leucine into isolated chloroplasts from Nicotiana tabacum. The incorporation activity varied greatly during the year, being largest in the winter and smallest in the summer. Conversely, the relative effect of kinetin on the incorporation of ¹⁴C-leucine, whether applied as a pretreatment to the leaves or directly in the incubation medium, was largest in the summer and smallest or absent altogether in the winter. Kinetin did not prolong the net incorporation period, which lasted about 40 min, but only enhanced the initial rate of the reaction. Chloroplasts extracted from leaves that had been detached for 24 or 48 h displayed very little of their original, pre-aged incorporation activity and treating the leaves with kinetin did not, essentially, prevent this loss. It was concluded that the major effect of kinetin upon chloroplasts may be related primarily to an effect upon hydration and permeability of the chloroplast and its membranes, and not to an effect directly upon its machinery for protein synthesis.     

Therapeutic Effect of Kinetin on Tobacco Alternariosis

LESIONS produced by Alternaris tenuis on tobacco leaves consist of fungal invaded, necrotic centres surrounded by well demarcated, non-invaded, chlorotic haloes^1,2, though necrosis does occur without chlorosis following infection of leaves in advanced senescence³. Alternariol monomethyl ether (AME)⁴ and tenuazonic acid⁵ have been implicated as chlorosis inducing metabolites (CIM) but other metabolites^6,7 may be involved. CIM are readily detoxified in young, living tissue⁶, though tenuazonic acid seems to be fairly stable⁵. Under uniform conditions, infection of progressively older leaf tissues results in lesions with chlorotic halos of increasing width^1,3 which suggests that the CIM are detoxified less readily or are synthesized more abundantly as the host tissue ages.     

Effects of Auxin and Kinetin on the Development and Differentiation of Potato Tissue Cultured in vitro

The present investigation deals with the influence of auxin and kinetin on cultures of potato tuber tissue, and the effect of the size of the explants on the organ formation. Exogenous application of auxin is indispensable for initiating callus formation of the tissue, but kinetin is not necessarily required. Kinetin serves to maintain the callus development, indicating that the stimulation of callus growth due to exogenous auxin would presumably be mediated by the addition of kinetin to the medium. A relatively low concentration of auxin in the medium is required for root formation on the culture. In this case, IAA is markedly superior to any other auxin in root forming activity. NAA is somewhat less effective than IAA, and 2,4-D shows no stimulation on root formation. The growth and organ formation of potato tissue are remarkably affected By the variation in sizes of the explants. Spontaneous formation of a sprout was observed on the large explant in the medium without auxin. Small explants form only callus or roots in the presence of auxin and kinetin irrespective of combination or concentration. It seems likely that a sufficient amount of stimulus for initiation of bud formation may be contained in the large sized explant itself.     

Effects of NaCl on vascular responsiveness in male rats

The effect of chronic salt treatment on systolic blood pressure and vascular adrenergic responsiveness was studied in rats. Vascular reactivity of aortic smooth muscle to potassium chloride and sodium nitrite was similar in both groups, indicating that salt treatment did not alter the regular contraction and relaxation process of the smooth muscle. Isoproterenol-induced relaxation was similar for both treated and control groups demonstrating that salt treatment had no effect on vascular beta-adrenergic responsiveness. However, when aortic smooth muscle was incubated with angiotensin II or norepinephrine, a significant increase in responsiveness was observed in the aortic smooth muscle of the salt-treated group compared to the control group. Collectively, these results suggest that salt, per se, does not affect systolic blood pressure or peripheral beta-adrenergic responsiveness, but does result in a significantly enhanced alpha-adrenergic responsiveness. The implication of these results for experimental hypertension are discussed.     

Nitrate, Ammonium and Kinetin Effects on Growth and Enzyme Activities of Paul's Scarlet Rose Callus

Factorial experiments using the three variables nitrate, ammonium, and kinetin at six different concentrations each (nitrate 4.64 to 215 mM; ammonium 2.15 to 100 mM; and kinetin 0.1 to 4.64 mg/l) were set up to measure the effects of each of these factors, and their interactions, on the fresh weight, protein, and enzyme activities of callus of Paul's Scarlet Rose. Optimum fresh weight values were obtained with nitrate at 46.4 mM. Ammonium inhibited growth at concentrations above 2.15 mM, and kinetin had no significant effect. Significant interaction between nitrate and ammonium effects on growth was found. Kinetin did not interact significantly with either nitrate or ammonium to influence the fresh weight. The specific activity of glutamate dehydrogenase (NAD) in the aminating reaction increased with increasing ammonium concentrations to 21.5; at higher concentrations the activity remained high. Glutamine synthetase specific activity was constant over a large range of nitrate and ammonium concentrations, increasing only when nitrate went from 46.4 to 100 mM. Glutamine synthetase was sensitive to the nitrate: ammonium interaction. Specific activity decreased at progressively higher ammonium levels when nitrate concentration increased. No glutamate synthase activity was detected at optimal nitrate concentrations.