The effect of polyamines on leaf senescence in two diverse rose species

Polyamines (PAs) retarded the senescence of leaf discs of two diverse speciesof rose viz., Rosa bourboniana andRosa damascena, while polyamine biosynthetic inhibitorsdifluoromethylornithine (DFMO), difluoromethylarginine (DFMA), methylglyoxal-bis(guanylhydrazone) (MGBG) and abscisic acid (ABA) promoted senescence. Sperminewas significantly the most effective polyamine in retarding senescence inR. bourboniana while MGBG and DFMA were more prominent inaccelerating senescence in R. damascena and R.bourboniana respectively. Protein and RNA content were significantlyhigher in polyamine treated leaf discs compared to those treated with polyaminebiosynthetic inhibitors and ABA. Total and reducing sugars decreased under alltreatments while the starch content increased significantly only in polyaminetreated leaf discs. Peroxidase and cellulase activities were retarded bypolyamine treatments and accelerated by polyamine biosynthetic inhibitors andABA. The role of PAs is discussed in relation to senescence.     

Polyamines and carnation flower senescence: Endogenous levels and the effect of applied polyamines on senescence

The polyamines putrescine and spermine were effective in delaying the senescence of carnation buds, but were ineffective when applied to flowers of which the petals had already opened, and were 90° with respect to the stem. Higher levels of endogenous putrescine were detected in the open flowers than in the buds, and this may explain the negative effect obtained when polyamines were applied to open flowers that were picked for commercial distribution.Abbreviations AOA amino-oxyacetic acid - AVG amino-ethoxyvinyl-glycine - SAM S-adenosyl methionine - STS silver thiosulphate     

Pollination-induced senescence of Phalaenopsis petals

The longevity of cut Phalaenopsis (Phalaenopsis hybrid, cv. Herbet Hager) flowers is normally 2 to 3 weeks. After pollination however, there was a rapid acceleration of the wilting process, beginning after only 24 h. Enhancement of senescence in several Phalaenopsis cultivars as well as in Doritaenopsis, Dendrobium and Cymbidium, was induced by successful pollination and only slightly or not at all by emasculation. Wilting of the flowers was accompanied by a loss of water from cells of the upper layer of the petals, leading to their upward folding. Following pollination there was an increase in ethylene production and sensitivity to ethylene. The increase in ethylene production began about 10 h after pollination and reached its peak after 30 h. An obvious increase in sensitivity to ethylene could already be detected 4 h after pollination and reached its peak 10 h after pollination. The increase en ethylene sensitivity following pollination was not dependent on endogenous ethylene production as it occurred also in flowers treated with (aminooxy)acetic acid, an inhibitor of ethylene biosynthesis.Abbreviations AOA = (aminooxy)acetic acid - RH = relative humidity - SEM = scanning electron microscope     

Roles of pollination and short-chain saturated fatty acids in flower senescence

Pollination induced an immediate increase in ethylene production in Dianthus caryophyllus and Petunia hybrida. In Cymbidium, a lag of several hours was observed. In all three species, pollination induced premature flower senescence. Treatment of the stigmatic surface with aminoethoxyvinylglycine prior to pollination effectively blocked the increase in ethylene production and alleviated the detrimental effect of pollination on flower life.In all three tested species, octanoic and decanoic acids, when applied to the stigmatic surface, had no effect on ethylene production and flower life. In isolated Cymbidium lips placed with their cut base in solutions containing these fatty acids, no effects on red colouration, ethylene production, and ethylene forming enzyme activity were observed. In addition, ethylene sensitivity of isolated lips was not affected. The putative regulatory role of short-chain saturated fatty acids in (pollination-induced) flower senescence is discussed.     

Effects of applied auxin,gibberellin and cytokinin on the activity of peroxidases in the peduncles of rose flowers

The activity of peroxidases in the proximal part of the flower peduncle of rose cv. Nubia was promoted by exogenous application of auxin but not by gibberellin or cytokinin. In cv. Mercedes the activity was promoted also by gibberellin and cytokinin. In the distal parts of the peduncles of both cultivars, peroxidase activity was not affected by any of the applied growth regulators. In young flowers of cv. Nubia the protein content of the penduncles was affected only by cytokinin, and in aged flowers only by auxin, while in Mercedes peduncles the content of protein was not affected by any of the applied growth regulators. The specific activity of peroxidases was promoted by auxin in peduncles of Nubia and by both auxin and cytokinin in peduncles of Mercedes flowers.     

Changes in endogenous polyamines during flower development in two diverse species of rose

Changes in the concentrations of endogenous free, conjugated and bound polyamine were determined in petals of two different species of rose, viz. Rosa damascena and Rosa bourboniana, from small bud (stage 1) till full bloom (stage 8). High free putrescine and spermidine concentrations were associated with early stages of flower development and then decreased in R. damascena. At full bloom, the concentration of free putrescine was higher than rest of the polyamines measured. A steady increase in conjugated putrescine, spermidine and spermine was observed during entire period of flower development with predominance of conjugated putrescine at full bloom. In R. damascena the bound spermine was higher than rest of the polyamines during full bloom. In R. bourboniana, during the early stages of flower development, similar situation was observed, however, at full bloom, free spermidine concentration was higher than rest of the polyamines. In this species, the concentration of conjugated and bound spermine was higher than rest of the polyamines during full bloom. Polyamine concentrations were generally lower in the petals of R. bourboniana than R. damascena which may be due to genotypic differences. The possible roles of the observed polyamines are discussed in relation to flower development.IHBT Communication no, 0345.     

Effects of thidiazuron on micropropagation of rose

Summary Rose (Rose hybrida L.) plants were micropropagated by axillary shoot proliferation method. Maximum number of microshoots per shoot tip explant were obtained on MS medium supplemented with 5 to 10µM thidiazuron (TDZ). The microshoots formed rooted plants on MS hormone-free medium. No difference in the rooting of microshoots produced on medium containing TDZ or N⁶-benzyladenine was observed. The regenerated plants were successfully transplanted to the field and appeared similar to the parent plant in morphologic features.     

Changes in abscisic acid and phenols during flower development in two diverse species of rose

Changes in endogenous abscisic acid (ABA) and phenols were determined in petals of two diverse species of rose, viz., Rosa damascena Mill and Rosa bourboniana Desport during flower development. A progressive increase in free ABA was observed during flower development till full bloom in both the species with higher content of free ABA in Rosa damascena. While bound ABA level increased in Rosa damascena till stage 6, in Rosa bourboniana it continued to increase till full bloom. Acidic phenols increased slowly in both the species till stage 4, but sharply afterwards and no significant differences were noticed during full bloom period. Bound phenols content was higher in Rosa damascena during full bloom period. The significance of these changes in relation to flowering in the two diverse species of rose is discussed.     

Effects of temperature on phyllody expression and cytokinin content in floral organs of rose flowers

Formation of leaf-like organs known as phylloids in Rosahybrida cv. Motrea flowers was promoted by exposure of plants toelevated temperatures. At a day/night temperature regime of26°C/21°C respectively theproportion of malformed flowers exhibiting phyllody was four times higher thanthat in flowers of plants grown at21°C/15°C. The number ofpetals in phyllody-expressing flowers was higher than that in normal flowers.The total content of endogenous cytokinins in young flower buds of plantsexposed to the lower temperature was six times higher than that at the highertemperatures. The effects of the reduced temperature were pronounced on all thegroups of cytokinins examined. However, the proportion of the various cytokiningroups remained similar at both temperature regimes. In contrast to thecytokinins in the flower buds, the content of all cytokinin types in youngleaves increased following exposure to the higher temperature and was reducedbythe lower temperatures. After 11 weeks at the lower temperature, about18% of the flowers remained malformed, whereas at the higher temperatureabout 20% of the flowers still remained normal. All thephyllody-exhibiting flowers were formed on vigorously grown basal shootscharacteristic to Rosa hybrida plants, whereas the normalflowers at the elevated temperatures were formed on lateral shoots which weremost distal to the plant base. However, irrespective of the season, thepresenceof normal and malformed flowers was observed on plants kept growing at standardconditions of 30°C/17°C inthegreenhouse. This phenomenon led us to examine the cytokinins in floral organsofnormal and malformed cv. Motrea flowers grown in the greenhouse as well as inflowers of a complete rose mutant known as a 'Green Rose(Rosa chinensis viridiflora). The highest content ofcytokinins was found in the pistils and stamens of normal 'Motreaflowers. On the other hand, the content of cytokinins in leaf-like style-tubesin the malformed flowers as well as in partially malformed ovaries at the baseof phylloids was significantly lower. A low content of cytokinins was alsopresent in petals of both normal and phyllody-exhibiting flowers and the lowestcontent has been found in the phylloids of the 'Green Rose. Apossibility of mutant deviations in metabolism of cytokinins in rose plants isdiscussed.     

Hormonal regulation of flower senescence in roses (<Emphasis Type="Italic">Rosa hybrida</Emphasis> L.)

To elucidate the role of the plant hormones—abscisic acid (ABA) and ethylene during flower senescence in roses, experiments were conducted on two cultivars of cut-roses (Rosa hybrida L.), ‘Grandgala’ and ‘First Red,’ obtained from a commercial grower. An apparent similarity was observed during flower senescence and accumulation of endogenous ABA in petal tissue. Several fold increase in ABA concentration was observed during the later stages of senescence which was found to be associated with a drastic reduction of flower water potential and water uptake. During the later stages of senescence (S5–S6) higher ABA concentration coincides with the elevated concentration of ethylene production. ABA and ethylene both stimulate senescence and are suggested to interact during flower senescence under water limitations.     

Identification of the cytokinins in red pine seedlings

Zeatin-9-riboside was identified in shoots and roots of Pinus resinosa by GC-MS analysis of its permethyl derivative. Based on their chromatographic properties on Sephadex LH-20 and C₁₈ HPLC, and their susceptibility to enzymatic degradation, several other cytokinins have been tentatively identified. The basic fraction of both the roots and shoots contained zeatin, whereas the shoots contained dihydrozeatin-O-glucoside and the roots contained zeatin-O-glucoside. Zeatin-9-riboside monophosphate, isopentenyladenosine monophosphate ([9R-5P]iP) and glucosyl phosphate derivatives were detected in the acidic fractions from both roots and shoots. There were equivalent amounts of [9R-5P]iP in both roots and shoots. The presence of equivalent amounts of [9R-5P]iP in both the roots and shots suggests that cytokinin biosynthesis may be occurring in both locations.Abbreviations AMP adenosine-5-monophosphate - BAP benzylaminopurine - BSA bovine serum albumin - BuOH butan-1-ol - CK cytokinin - (diH)Z dihydrozeatin - (diH OG)Z dihydrozeatin-O-glucoside - (diH OG)[9R]Z dihydrozeatin-9-riboside-O-glucoside - DW dry weight - EtOH ethanol - FW fresh weight - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - [9R]iP isopentenyladenosine - [9R-5P]iP isopentenyladenosine monophosphate - MeOH methanol - PVP polyvinylpyrrolidone - RFE rotary film evaporation - TEAB triethyl ammonium bicarbonate - Z zeatin - [9R]Z zeatin-9-riboside - (OG)Z zeatin-O-glucoside - [7G]Z zeatin-7-glucoside - [9R-5P]Z zeatin-9-riboside monophosphate     

Influence of season on rose pollen quality

Summary In vitro tests of pollen germination were carried out at different periods during an annual cycle in order to study environmental influence on the quality of Rosa hybrida L. pollen during its maturation process. This quality was evaluated by taking into account the rate of germination as well as the average length of emitted pollen tubes. In addition, during an annual hybridization period, a few pollinations were carried out in vivo with pollen of the same origin in order to study the evolution of the fertilization results, as attested by number of achenes per resulting hips. During the period covered by the experiments, the evolution of the pollen quality detected in vitro can be related to that of seed setting success. Of the two criteria used in vitro to evaluate pollen quality, the factor most liable to influence in vivo fertilization success seems to be the average length of emitted pollen tubes.     

Enhancement of petunia and dendrobium flower senescence by jasmonic acid methyl ester is via the promotion of ethylene production

Methyl jasmonate (JA-Me), applied to dendrobium and petunia flowers either as an aqueous solution through the cut stem or stigma, or as a gas, accelerated senescence. The rate of appearance of wilting symptoms was directly related to the amount of JA-Me applied to the flowers. JA-Me increased ethylene production by the flowers, irrespective of application method, and this effect was also proportional to the dose of the compound. In both dendrobium and petunia flowers, the JA-Me induced increases in ethylene production and 1-aminocyclopropane-1-carboxylic acid content followed similar patterns. Aminooxyacetic acid, an inhibitor of ACC-synthase, and silver-thiosulfate, an inhibitor of ethylene action, completely inhibited the effects of JA-Me. It is concluded that JA-Me enhances petunia and dendrobium flower senescence via the promotion of ACC and ethylene production.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AOA aminooxyacetic acid - Fl flower - JA jasmonic acid - JA-Me jasmonic acid methyl ester - LOX lipoxygenase - PLase A A-type phospholipase - STS silver-thiosulfate     

Endogenous cytokinins in the vegetative and reproductive phases of development in the dioecious plant Rumex acetosella L.

The content of endogenous cytokinins has been analysed in leaf and inflorescence extracts of male and female R. acetosella plants, using gas chromatography. Plant parts were extracted at four stages of development: leaves of juvenile plants, leaves of adult plants at the time of flower initiation and in full bloom, and upper internodes of the inflorescence stalks. Cytokinins with characteristics similar to isopentenyl adenine and adenosin, zeatin, zeatin riboside, and a bound form of zeatin, were all found in the extracts. The total amount of cytokinins was higher in female than in male plants during all these stages.Reprint requests     

Optimization of primer screening for evaluation of genetic relationship in rose cultivars

Optimization of primer screening for evaluation of genetic relationship in 34 cultivars of rose through random amplified polymorphic DNA (RAPD) markers was investigated. Four series of decamer primers were used for screening and optimization of RAPD analysis between which A and N series performed good amplification of fragments as compared with other series. The primers OPN-07 and OPN-15 produced maximum number of DNA fragments in Rosa hybrida cv. Anuraag. Some primer either did not produce amplification or produced very poor amplification. Further, ten selected primers were used for genetic analysis of 34 rose cultivars. The primer OPN-15 amplified 21 fragments in all cultivars tested. A total of 162 distinct DNA fragments (bands) ranging from 100 to 3400 base pairs were amplified by using 10 selected random primers. The cluster analysis indicated that these rose cultivars formed nine clusters.     

Control of direct and indirect somatic embryogenesis by exogenous growth regulators in immature zygotic embryo cultures of rose

Immature zygotic embryos of rose (Rosa hybrida L.; cv. Sumpath) did not form somatic embryos or embryogenic calluses when cultured on half-strength Murashige and Skoog's medium supplemented with various con-centrations of 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole growth regulator. However, the zygotic embryos produced somatic embryos without an intervening callus phase at a frequency of 27.3% on medium with 4.44 M 6-benzyladenine (BA) alone. Immature zygotic embryos formed embryogenic calluses at a frequency of 25% on medium with a combination of 1.36 M 2,4-D and 4.44 M BA. Upon transfer to medium without growth regulators, embryogenic calluses produced numerous somatic embryos that subsequently developed into plantlets. Somatic embryos were induced directly from immature zygotic embryos, or indirectly via an intervening callus phase, by manipulating the exogenous growth regulators. Plantlets were successfully transplanted to potting soil and grown to maturity in a greenhouse.     

Effects of cotton rootstock on endogenous cytokinins and abscisic acid in xylem sap and leaves in relation to leaf senescence

Leaf senescence varies greatly among cotton cultivars, possiblydue to their root characteristics, particularly the root-sourcedcytokinins and abscisic acid (ABA). Early-senescence (K1) andlate-senescence (K2) lines, were reciprocally or self-graftedto examine the effects of rootstock on leaf senescence and endogenoushormones in both leaves and xylem sap. The results indicatethat the graft of K1 scion onto K2 rootstock (K1/K2) alleviatedleaf senescence with enhanced photosynthetic (Pn) rate, increasedlevels of chlorophyll (Chl) and total soluble protein (TSP),concurrently with reduced malondialdehyde (MDA) contents inthe fourth leaf on the main-stem. The graft of K2 scion ontoK1 rootstock enhanced leaf senescence with reduced Pn, Chl,and TSP, and increased MDA, compared with their respective self-graftedcontrol plants (K1/K1 and K2/K2). Reciprocally grafted plantsdiffered significantly from their self-grafted control plantsin levels of zeatin and its riboside (Z+ZR), isopentenyl andits adenine (iP+iPA), and ABA, but not in those of dihydrozeatinand its riboside (DHZ+DHZR) in leaves in late season, whichwas consistent with variations in leaf senescence between reciprocallyand self-grafted plants. The results suggest that leaf senescenceis closely associated with reduced accumulation of Z+ZR, andiP+iPA rather than DHZ+DHZR, or enhanced ABA in leaves of cotton.Genotypic variation in leaf senescence may result from the differencein root characteristics, particularly in Z+ZR, iP+iPA, and ABAwhich are regulated by the root system directly or indirectly. Key words: Abscisic acid, cotton, cytokinins, grafting, leaf senescence Received 23 October 2007; Revised 17 January 2008 Accepted 23 January 2008     

Water relations and growth of rose plants cultured in vitro under various relative humidities

Stomatal malfunctioning is one of the main reasons why plants desiccate when transferred from in vitro to greenhouse conditions. In order to overcome this problem in Rosa hybrida cv. Madame G. Delbard (R) Deladel, two techniques, bottom cooling and water vapour permeable lid, were used. Both methods aimed to increase the vapour pressure gradient between leaf and atmosphere and consequently to improve plant transpiration.The results showed that these techniques increased leaf resistance to dehydration and improved stomatal regulation. Water relations of treated plantlets were similar to those generally observed in hardened plants: lower leaf water and osmotic potentials, and lower leaf water content than in the control ones. Osmotic adjustment occurred in treated plantlets maintaining turgor pressure. Each technique also induced some effects on growth during the rooting phase: with bottom cooling, roots were shorter, with permeable lids, apices were necrosed.These results are discussed in terms of physiological causes and in terms of effect during the following acclimatization.Abbreviations AWC absolute water content - DW dry weight - FW fresh weight     

Leaf water and carbohydrate status of VA mycorrhizal rose exposed to drought stress

Summary Shoot water relations and carbohydrate levels were compared for droughted nonmycorrhizal and vesicular-arbuscular (VA) mycorrhizalRosa hybrida L. cv ‘Samantha’ plants grown with high and low phosphorus fertilization. Leaf diffusive conductance (g _i ) of plants colonized byGlomus intraradices Schenk and Smith andGlomus deserticola Trappe, Bloss and Menge were 2 × and 1.5× greater, respectively, than in nonmycorrhizal plants. Regardless of P fertilization, leaf osmotic and bulk water potentials were 0.5 to 1.1 MPa higher in mycorrhizal than in nonmycorrhizal plants. Leaf starch, chlorophyll and water contents while fructose, glucose and total soluble carbohydrates were lower. Level of P fertilization had no effect on water relations or soluble carbohydrate content of nonmycorrhizal roses. The water status of droughted rose was impoved more byG. intraradices than byG. deserticola. Washington State University College of Agriculture and Home Economics Research Center Scientific Paper No. 7375.