Kinetin Solution Research Articles

Effects of kinetin on growth, grain yield and some mineral elements in wheat plants growing under excess salinity and oxygen deficiency

Wheat plants, 22d. old, were exposed to wide range of soil water osmotic potential (Ψs = 0 to −1.2 MPa) induced by NaCl and CaCl2 treatments in combination with roots maintained under aerobic (drained at field capacity) or nonaerobic (flooded) conditions in the soil, and sprayed with 10 mg L−1 kinetin solution. In drained plants, not receiving kinetin, increased soil salinity resulted in appreciable inhibition of shoot growth and reduction in chlorophyll (Ch1.), soluble sugars (SS) contents and grain yield. Shoot growth, Ch1. content, soluble sugars and grain yield were significantly lower for flooded plants than unflooded analogues over the entire Ψs range. Both salinity and waterlogging synergize to increase Na+, Ca+ and Cl− accumulation in shoot tissues and to decrease the stability of leaf membranes to either dehydration (40% polyethylene glycol 6000) or heat (51 °C) stress. The ratio of K+/Na+ transported to shoots under aerobic and anaerobic conditions decreased progressively on salinization. The association between the internal mineral element concentrations was largely affected by kinetin treatment. Kinetin application ameliorated the deleterious effects of salinity and oxygen deficiency. It reduced Na+, Ca2+ and Cl− accumulation and improved K+ uptake under salinity and waterlogging stresses. Increased K+/Na+ ratio helped the plants to avoid Na+ toxicity and enhanced shoot growth and grain yield. Kinetin also reduced membrane injury by dehydration and heat stresses and improved the water status of plants under both aerobic and anaerobic conditions. The effects of single factors (Soil salinity ‘Ψs’, soil waterlogging ‘WL’ and Kinetin ‘Kin’) and their interactions (Ψs × WL, Ψs × Kin, WL × Kin and Ψs × WL × Kin) were shown by analysis of variance to be statistically significant for most parameters tested. Calculation of the coefficient of determination (η+) led to three important findings. (1) Salinity (Ψs) was dominant in affecting leaf relative water content (RWC), shoot dry mass, grain yield, stability of leaf membranes to dehydration stress and the contents of Na+, Ca2+, Mg2+ and Cl−. (2) Kinetin (Kin) had a dominant effect on the stability of leaf membranes to heat stress as well as on chlorophyll and soluble sugars contents. (3) The share of waterlogging (WL) was dominant for K+ content. It can be concluded that kinetin application helped wheat plants to grow successfully in the areas subjected to combined effects of salinity and oxygen deficiency, such as in salt marshes.

Efficacy of Treatments for Delaying Senescence of Wheat Leaves: I. Senescence under Controlled Conditions

AbstractSenescence of wheat (Triticum aestivum L.) leaves is accelerated by high temperature during the critical grain filling period. Loss of leaf viability decreases grain yields and the response to production inputs. Studies were conducted under controlled conditions to identify treatments that might delay the rapid senescence induced by high temperature. Shoots of 30‐d‐old seedlings of ‘Nesma’ wheat were immersed in 0.1 mM solutions of kinetin, abscisic acid, or one of six mineral salts [0.1 mM Ca(NO3)2, NaH2PO4, K2SO4, KH2PO4, KNO3, or NH4H2PO4] and incubated at 20 and 30°C with continuous irradiance of 150 μmol m−2 s−1. Chlorophyll and free amino acid concentrations and crude protease enzyme activity were monitored over an 8‐d period as measures of shoot senescence. High temperature and abscisic acid generally increased all senescence processes, whereas kinetin and several mineral salts reduced the loss of chlorophyll and slowed the increases in amino acid concentration and protease activity compared with amounts in shoots incubated in distilled water. Mineral salts that contained N or P were usually most effective, particularly in countering rapid senescence at 30°C relative to 20°C. We conclude that senescence processes induced by high temperatures in detached shoots resemble those in whole plants and that the feasibility of delaying senescence by foliar application of selected compounds under field conditions merits investigation.

EFFECT OF FOLCYSTEINE AND KINETIN ON `KAPOHO' PAPAYA (CARICA PAPAYA)

Flowering plants of `Kapoho' papaya were sprayed with aqueous solutions of kinetin and folcysteine. Plants were treated four times at 3-week intervals with 0-, 50-, 90-, or 130-ppm solutions of either biostimulant or their combinations. Fruit number, size, and weight were recorded weekly during 15 weeks after treatment. Folcysteine treatment at 90 to 130 ppm significantly increased `Kapoho' papaya yield. Kinetin treatment alone did not significantly affect fruit yield at any rate tested. Moreover, none of the kinetin plus folcysteine combinations significantly differed from the control in terms of fruit yield. These findings suggest that folcysteine rates of 90 to 130 ppm can increase fruit yield in this cultivar, and that kinetin had an antagonistic effect on the activity of folcysteine on the yield of `Kapoho' papaya.

Chlorophyll Biosynthetic Reactions during Senescence of Excised Barley (Hordeum vulgare L. cv IB 65) Leaves.

The chlorophyll (Chl) biosynthetic reactions were monitored during senescence of dark-incubated excised barley (Hordeum vulgare L. cv IB 65) leaves floated in double-distilled water or kinetin solution. Kinetin abolished the degradation of Chl but failed to check the net degradation of protochlorophyllide (Pchlide), suggesting that different sets of enzymes, i.e. kinetin sensitive and insensitive, are responsible for the degradation of Chl and Pchlide, respectively. Upon exposure of the leaves to light, the dark-accumulated Pchlide was efficiently phototransformed to chorophyllide (Chlide), even on the 7th d of dark incubation, demonstrating that the activity of Pchlide reductase, one of the late enzymes of the Chl biosynthetic pathway, is not substantially affected during senescence. The senescing leaves continued to synthesize Pchlide and Chlide until the 7th d, although at a reduced rate (20% of the 1st d). The decline of the rate of synthesis of Pchlide and Chlide is due to the loss of activity of two early enzymes of the Chl biosynthetic pathway, i.e. 5-aminolevulinic acid dehydratase and porphobilinogen deaminase. Kinetin substantially checked the loss of activity of these two enzymes.

The combined effects of acidification stress and kinetin on chlorophyll content, dry matter accumulation and transpiration coefficient inSorghum bicolor plants

Increasing soil acidity (from pH 6.5 to pH 2.0) decreased chlorophyll (Chl)a andb contents, dry matter accumulation by plants and the transpiration coefficient. Chl stability to heat significantly increased with increased soil acidity. The Chla/b ratio was increased significantly at pH 5 and 4 and decreased at pH 3 and 2. SprayingSorghum shoots with kinetin solutions counteracted the above adverse effects on Chl content and dry matter accumulation. Kinetin-treated plants showed a lower transpiration coefficient than the untreated plants.

Lipid mobilization in Citrus cotyledons during germination

In the present work, lipid mobilization in C. limon (L.) Burm. f. cotyledons and the axial control of this process were studied. Two lipases were found in extracts from cotyledons: one with optimal activity at pH 5.0 (acid lipase) and another with a pH optimum between 7.5-8.0 (alkaline lipase). Both lipase activities showed a parallel pattern of evolution, increasing to a peak by the 16th day of germination. Most acid lipase activity was recovered in the fat layer obtained from crude extracts, and the alkaline lipase was located mainly in the glyoxysomes. The rate of lipid breakdown was lower in excised cotyledons when compared with intact ones. However, substantial hydrolysis of lipids occurs in the absence of the axis. In excised cotyledons, both acid and alkaline lipase activities were markedly reduced, indicating that the presence of the axis was necessary for maximum enzyme formation. Also, development of isocitrate lyase activity was partially inhibited by removal of the axis. The inhibition of isocitrate lyase activity observed when cotyledons were detached from the embryo cannot be explained by the source-sink model, as glucose and sucrose levels were lower in excised cotyledons than in intact ones. Incubation of excised cotyledons in gibberellic acid (10 -5 M) or kinetin (10 -4 M) solutions was effective in maintaining the development of lipase activities at similar levels than in intact cotyledons. Gibberellic acid (10 -5 M) produced a stimulation of isocitrate lyase activity in excised cotyledons, but not reaching the activity level developed by intact cotyledons. The data presented indicate that lipolysis in Citrus cotyledons seems to be only partially dependent on the axis. It is concluded that enzyme regulation in Citrus cotyledons cannot be entirely explained by hormonal control or source-sink relationships.

Stimulation of Germination of Seeds of Cowpea Witchweed (Striga gesnerioides) by Sodium Hypochlorite and Some Growth Regulators

Tests with 18 growth regulators and chemicals revealed that the cytokinins [zeatin, kinetin, and 6-benzylaminopurine (BAP)], ethylene, and sodium hypochlorite stimulate germination of cowpea witchweed seeds at various concentrations. Witchweed seeds preconditioned in different concentrations of sodium hypochlorite for 3 wk had germination rates of 25 to 89% after incubation in distilled water, 10−5M solution of kinetin, 50 mg L−1of 2-chloroethylphosphonic acid, and exudates from cowpea roots. Witchweed seeds preconditioned in distilled water and subsequently incubated in distilled water did not germinate.

Cytological studies of the hypersensitive death of cowpea epidermal cells induced by basidiospore-derived infection by the cowpea rust fungus

The cytological responses to the monokaryotic primary hyphae of the cowpea rust fungus (Uromyces vignae Barcl.) were observed in vein epidermal cells of a resistant and a susceptible cowpea cultivar. Unlike the previously examined response to haustoria of a nonpathogenic powdery mildew fungus, plant cell walls did not become autofluorescent in response to fungal penetration, and the primary hypha only rarely became encased. Following fungal penetration, the response of invaded cells of the resistant, intact plant could be divided into the following stages: (I) cytoplasmic streaming normal; (II) cytoplasmic streaming slow or stopped, Brownian motion of particles visible in the vacuole, granulated cytoplasm aggregated along the cell walls, some host nuclei disappeared; and (III) protoplast collapsed. Epidermal tissue of the resistant cultivar did not exhibit stages II–III when detached and mounted in water 12 h after inoculation and examined 9 h later. The frequency of stage III increased when the tissue was mounted in CaCl2, Ca(NO3)2, and KNO3, but only in a kinetin solution did it approximate that in attached tissue. Although kinetin inhibited fungal growth in both the resistant and the susceptible cultivar, the hypersensitive response occurred only in the former, suggesting that kinetin affects the hypersensitive response directly rather than through its inhibitory effect on the fungus. Key words: cowpea, Vigna unguiculata, cowpea rust fungus, Uromyces vignae (Barcl.), hypersensitivity.

The effect of ethylene and other regulators on coleoptile growth of rice under anoxia

Caryopses of rice ( Oryza sativa L. cultivar ‘Mercury’) were imbibed for 2 days in water or 10 μM solutions of indoleacetic acid (IAA), kinetin, gibberellic acid or abscisic acid in the presence of a gas stream of air or nitrogen. Fully-imbibed caryopses were placed on agar in vertically-maintained Petri dishes in chambers in the dark at 29°C. Subsequent growth of roots and coleoptiles in air or nitrogen, with the later addition of 10 μ1.1 −1 ethylene, was determined. Rice seedlings grown in total anoxia in a nitrogen stream did not develop roots, but could do so if air or 0.5% oxygen was introduced after 3 or 4 days of anoxia. Coeloptile elongation in nitrogen proceeded at a rate comparable to that in air over the 5-day experimental period. Treatment of seedlings in air, during imbibition or during subsequent growth, with indoleacetic acid, gibberellic acid or ethylene promoted coleoptile elongation. The growth of coleoptiles in nitrogen was not enhanced in the presence of these growth promoters, and was inhibited by treatment with abscisic acid or kinetin. The role of endogenous regulators in cellular elongation under anoxia is discussed.

Effects of Water Deficiency and Kinetin on Growth and Nitrogen Metabolism of Cowpea Plants

AbstractCowpea plants (Vigna sinensis Savi.) were grown in pots for two successive years. These plants were daily maintained water holding capacities (15, 25, 45, 65 %).The foliage of plants grown at every level of soil moisture was sprayed till dripping with kinetin solutions (0, 10, 20, 40 mg/1) three times after, 3, 6 and 9 weeks from sowing. Samples were taken at the two physiological stages before flowering and during flowering for growth measurements and determination of nitrogen fractions.Water shortage led to retardation of stem length, number of internodes, number of leaves and dry weight of shoots. Kinetin reduced stem length of cowpea shoots. On the other hand, it exhibited stimulative effect when applied at concentrations 10 and 20 mg/1 on number of internodes, and dry weight of shoots.Water stress decreased total–N and protein–N contents of cowpea shoots. On the other hand total soluble–N content was increased under the same conditions. Kinetin increased total–N and protein–N contents of cowpea shoots. Meanwhile, the same growth regulator decreased total soluble–N when applied at 45 %, 25 % and 15 % W.H.C. levels.

Combined Effect of Soil Water Availability and Growth Substances on Some Aspects of Chemical Composition of Cowpea Plants

AbstractCowpea plant (Vigna sinensis Savi) were grown in pots for two successive years. These plants were daily maintained at water holding capacities (15, 25, 45 and 65 %). The foliage of plants grown at every level of soil moisture was sprayed till dripping with either IAA solutions 0, 10, 50 and 100 mg/1 or kinetin solutions 0, 10, 20 and 40 mg/1 three times after 3, 6 and 9 weeks from sowing. Samples were taken at two physiological stages before flowering and during flowering for determination of photosynthetic pigments and carbohydrate fractions.Water stress decreased all photosynthetic pigments (chlorophyll “a”, chlorophyll “b” and carotenoids). Meanwhile, it increased the ratios of “a/b” and (a + b)/carotenoids. IAA and kinetin at all concentrations increased photosynthetic pigments. In addition, the same treatments led to decrease in the ratios of “a/b” and a + b/carotenoids.Total carbohydrate content was decreased by decreasing soil moisture content. Meanwhile, reducing sugars as well as sucrose contents were increased. IAA and kinetin increased total carbohydrate, reducing sugars and sucrose of cowpea shoots comparing with respective controls.

EFFECT OF KINETIN ON GROWTH, FLOWERING, YIELD AND CHEMICAL COMPOSITION OF FRUIT OF TOMATO (Lycopersicon esculentum Mill.)

Plants of tomato (Lycopersicon esculentum Mill.) cv. Pusa Ruby were sprayed with an aqueous solution of kinetin at 0, 10, 50, 100 and 200 ppm. This biore- gulant increased the linear growth at all the used concentrations and stimulated the growth of lateral branches up to a concentration of 100 ppm and had no significant influence at 200 ppm. Kinetin increased the, number of leaves per plant and their area at 10-200 ppm. Quantitative promotion in flowering was observed in plants treated with kinetin. Application of kinetin enhanced the yield of fruits. Kinetin also increased juice, total soluble solids, sugars, protein and ascorbic acid contents of fruits but did not affect the acidity in tomato.

Effect of Kinetin on the Transcription Activity of Chromatin from Cucumber Cotyledons

Summary Three-day-old etiolated seedlings of Cucumis sativus L. cv. Monastyrski were sprayed with water or 0.1 mM kinetin solution, which led to an enhancement of expansion growth of the cotyledons. After 24 h in darkness, the cotyledons were harvested, chromatin was isolated and its transcription activity tested. Chromatin from kinetin-treated cotyledons exhibited higher activity, both endogenous and supported with exogenous Escherischia coli RNA polymerase, which pointed to a higher DNA template activity as compared with the untreated control. Addition of kinetin to the reaction mixture for RNA synthesis in vitro, as well as the presence of kinetin during homogenization of the cotyledons had no effect on the transcription activity of the chromatin. Kinetin inhibited elongation growth of the hypocotyls. Chromatin isolated from kinetin-treated hypocotyls displayed lower activity with respect to the untreated control. Also the presence of kinetin during hypocotyl homogenization led to a reduction of the transcriptional activity of the chromatin.

The relation between nitrogen deficiency and leaf senescence

Because the “mobilization” of nitrogen resulting from nutritional nitrogen deficiency is also prominent during leaf senescence, the characteristics of these two syndromes were compared. Oat plants (Avena sativa L. cv. Victory) were raised on a nutrient solution, complete except for nitrogen supply (i.e., with only the seed protein as nitrogen source), and the senescence of their leaves was compared with that of controls grown on a full nutrient solution. The N‐deficient plants flowered after forming only 4 leaves and each set a single seed. The nitrogen lack affected the content of chlorophyll somewhat more than the content of the amino acids or protein nitrogen. However, spraying the plants with kinetin solution was able to retain 20–30% of the chlorophyll and protein. During senescence, the chlorophyll appears to be less stable in the N‐deficient leaves than in the controls, while the protein is somewhat more stable than in the controls. Also, when the detached leaves from N‐deficient plants senesced in white light or in darkness, kinetin delayed their senescence almost as effectively as that of control leaves. Most strikingly, the stomata of N‐deficient leaves after detachment and floating on water were largely closed in light, just as in senescence, but could be partially induced to open by kinetin treatment. Since stomatal closure has earlier been shown to cause senescence, the characteristic syndrome of foliar nitrogen deficiency is concluded to be partly that of senescence.

Regulation of leaf senescence, grain‐filling and yield of rice by kinetin and abscisic acid

Senescence of rice (Oryza sativa L. cv. Jaya) leaves was regulated with kinetin and abscisic acid (ABA) sprays at the reproductive stage. The effect of such sprays on grain‐filling and yield was analyzed. Spraying 100‐day‐old plants with kinetin solution (100 μg ml‐1) significantly delayed senescence as indicated by higher total chlorophyll and protein levels in the three uppermost leaves compared with the controls. In contrast, spraying with ABA (15 μg ml‐1) significantly promoted foliar senescence. The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them. The possibility of increased grain‐filling and thus, yield due to delayed foliar senescence by kinetin treatment and decreased grain‐filling due to hastening of senescence by ABA is discussed.

Kinetin-Mediated Stimulation of Accumulation of Buckwheat Flavonoids in the Dark

A short treatment of excised buckwheat cotyledons with a solution of kinetin lead to an up to 9-fold stimulation of anthocyanin biosynthesis, to an about 50 percent increase in the accumula­tion of rutin, and to an about 30 percent increase, on the average, in the accumulation of C-glycosylflavones in the treated material during its posttreatment incubation in the dark. When the treated cotyledons were incubated in a solution of ʟ--phenylalanine anthocyanin accumulation in the dark practically attained the same high level as it was observed in the illuminated cotyledons fed with exogenous ʟ--phenylalanine. In experiments with l4C-labelled L-phenylalanine kinetin induced a sharp rise in the labelling (resp. in the utilization of exogenous substrate for biosynthesis) of anthocyanins and rutin in the dark and a slight increase in the radioactivity of C-glycosylflavones. Similar labelling changes occurred in the illuminated cotyledons. However, both kinetin and light still more effectively promoted biosynthetic use of the endogenous sub­strate. As a result the relative portion of flavonoids formed from exogenous L-phenylalanine under these conditions showed a decrease as compared with the ratio of precursor use in the un­treated cotyledons. The results show that low accumulation rates of anthocyanins and other flavo­noids in the dark are conditioned by the limited access of substrate (ʟ--phenylalanine) molecules to the flavonoid enzymes lending further support to the idea that flavonoid biosynthesis is normally controlled at the substrate rather than at the enzymic level.

Effect of Kinetin, Abscisic Acid, and Cations on Host‐Parasite Relations of Barley Inoculated with Erysiphe graminis f. sp. hordei

Kinetin, abscisic acid (AbA), and several cations were tested to determine what effect they have on resistance and susceptibility in detached primary leaf segments of barley (Hordeum vulgare L.) floating on water and inoculated with conidia of Erysiphe graminis f. sp. hordei Marchal, race CR3. Two nearly isogenic lines of Manchuria barley (Ml‐a, resistant and ml‐a, susceptible) were used for comparison. In both lines kinetin (0.1 mM) solution increased resistance. In Ml‐a AbA (0.1 mM) increased susceptibility. The increased susceptibility was the result of greater formation of apparently functional primary haustoria. The action of kinetin was antagonized by AbA and vice versa. Of the cations tested, Ca++, Mn++, and La+++ increased susceptibility in the Ml‐a line. These cations stimulated a greater production of secondary haustoria. None of the cations tested increased resistance. Combinations of AbA and cations were tested. AbA plus Mn++ or La+++ made the Ml‐a host as susceptible to the fungus as the ml‐a host. Senescence as measured by chlorophyll content was not correlated with susceptibility or resistance in either isogenic line.

Studies of the Effect of Root-cutting Treatment on Growth and Yield in Direct Sowing Culture of Paddy Rice : II. Changes in the physiological characteristics induced by root-cutting treatment and its relationship to growth behavior

In order to make clear thc mode of the occurrence of favorable effect of root-cutting treatment on the growth behavior of direct sown rice plants, several pot experiments were carried out from the view point of stress physiology. Result of the experiments and conclusion on causes of the occurrence of beneficial effect of root-cutting treatment as obtained from the first and second reports are summarized as follows: 1. Root-cutting treatment on the plants grown by direct sowing culture in well-drained paddy field brought about decreases in stomatal aperture, transpiration, and consequently, water stress on the plant due to lack of water balance, which is seen in the decrease of water content in the leaf and wilting of leaves. The investigation revealed that ethylene production increased in the plant body due to the water stress. 2. Root-cutting inhibited the production of cytokinin in the roots and checked its translocation to the plants grown above the ground surface, resulting in the decrease of chlorophyll content and increase of ethylene production in the leaf. Further investigation revealed that increase of ethylene production by the root-cutting treatment can be prevented by treating the leaves with kinetin solution. 3. The increase in ethylene production by root-cutting is due to water stress and inhibition of cytokinin translocation. It also lowers chlorophyll content in the leaf. However, as new roots emerged seven to ten days after the root-cutting treatment, absorption of nitrogen by roots increased along with reactivated cytokinin translocation. In consequence, chlorophyll content regained its level and after that it became higher than that in the control, and number of fresh leaves increased until later growing stages. 4. After the root-cutting treatment, physiological activity of thc roots, namely, oxidizing ability of α-Naphtylamine, was greatly enhanced due to the emergence of thick new roots and branched roots from the old remaining roots, which had also been accelerated by the treatment. This root activity lasted until the later growth stages. 5. The present experiment also suggested that thc increase of breaking strength which enhanced lodging resistance, observed in the previous report was presumably caused by the increase in ethylene produced in the plant until the later growth stages. 6. It was found that in the treated plants, physiological activity of the upper leaves to adapt themselves to drought condition was enhanced at the maturing stage; this was observed in the decrease of water content in upper leaves and of transpiration rate per unit leaf area, increase of diffusion pressure deficit (D P D) in the leaf blade, and of osmotic pressure in the cell, and decline of water potential in the leaf blade and panicle. The above-mentioned morphological, physiological and ecological changes in the rice plant induced by root-cutting treatment are reflections of water stress and of the changes of plant hormonal behaviour due to the treatment, which resulted in better ripening and increased yield of the rice plants.

Electron microscope studies on the morphogenesis of plastids. XI. Ultrastructural changes of the chloroplasts in tomato leaves treated with ethylene and kinetin.

Ultrastructural changes of the chloroplasts in the mesophyll cells of tomato plants which were exposed continuously to 2.0ppm ethylene up to 120hr were observed through the time course. At the same time, the effects of kinetin on the fine structure of chloroplasts were also examined. In the chloroplasts exposed to ethylene over 48hr, most of the normal membrane systems were decomposed and transformed into the macrograna. The chloroplasts exposed to ethylene for 48hr and then followed by 8 days water treatment had also macrograna in the stroma. However, the chloroplasts in the leaves undergoing natural senescence collapsed without the formation of macrograna. On the other hand, in the chloroplasts exposed to ethylene for 48hr and then followed by the incubation in kinetin solution (10mg/l) for 8 days, there were no formmtion of macrograna, and the thylakoid systems were kept with a little senescent symptom. To sum up, the ethylene exposure to tomato plants induces the formation of macrograna, plastoglobules and phytoferritin aggregates in the chloroplasts which are the significant characteristics of the chloroplast senescence. The kinetin treatment delays temporarily the chloro-plast senescence caused by ethylene exposure.

Kinetin Effect on Some Enzyme Activities during Senescence of Excised Rice Leaves as Subjected to Water Stress

Summary Excised rice (Oryza saliva L. cv. Ratna) leaves were subjected to water stress or kept turgid by floating them on water at a temperature of 27 ± 2°C. Catalase and alkaline pyrophosphatase activities decreased while peroxidase and acid pyrophosphatase activity increased faster in the water-stressed leaves during senescence. Infiltration of kinetin solution (10-6 M) into the leaves arrested the further rise in the peroxidase and acid PPase activities during senescence of turgid and water stressed leaves. On the other hand, catalase and alkaline PPase activities were retained at a higher level in kinetin-infiltrated leaves (both in turgid and water stressed conditions) in comparison to non-treated waterstressed leaves. It is concluded that kinetin-dependent control of enhancement of peroxidase and acid PPase activities and retardation of catalase and alkaline PPase activities is perhaps important n regulating the senescence of leaves induced by water stress.