Regulation of Inflorescence Growth in Cuttings of the Grape Vine (Vitis vinifera L.)

In woody cuttings of the grape vine inflorescences of fertilebuds usually atrophy soon after bud burst. Inflorescences areretained if leaves are removed from the elongating shoot, butremoval of apices and roots does not affect inflorescence growthif leaves are present. With defoliated cuttings, inflorescencegrowth is stimulated by removal of apices but depressed by removalof roots. Applications of indole acetic acid to the petiolestumps of defoliated cuttings did not replace the effect ofleaves and induce atrophy of inflorescences. Inflorescence growthin defoliated cuttings was inhibited by 2,4-dichlorophenoxyaceticacid (2,4-D), but concentrations which depressed inflorescencegrowth produced toxicity symptoms. Applications of 2,3,5-tri-iodobenzoicacid to petioles and leaf laminae were without effect on inflorescencegrowth. Treatment of inflorescences with the cytokinin 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine(SD 8₃₃₉) promoted inflorescence growth in both the presenceand the absence of leaves. Inhibitory effects of 2,4-D on inflorescencegrowth were partially reversible by application of SD 8₃₃₉.Response of inflorescences to gibberellic acid required eitherremoval of leaves or addition of SD 8₃₃₉.     

Effects of Temperature and Growth Regulators on Formation of Anlagen, Tendrils and Inflorescences in Vitis vinifera L.

The effects of single, combined and sequential application ofgibberellic acid (GA), chlormequat and cytokinins on the formationof anlagen, tendrils and inflorescences were studied in grapevines(cv. Muscat of Alexandria) grown with natural illumination athigh temperature (30 °C day to 25 °C night) and at lowtemperature (21 °C day to 16°C night or 18 °C dayto 13 °C night). GA promoted the formation of anlagen andgrowth of tendrils regardless of temperature, but inhibitedinflorescence production. Chlormequat had the opposite effecton anlagen formation and tendril growth and promoted inflorescenceformation from pre-formed anlagen or from tendril initials.While low temperature is normally unfavourable for inflorescenceformation, this was induced by chlormequat even at low temperature,but only with summer light conditions. Cytokinin application to plants pre-treated with chiormequatcaused tendrils to grow into inflorescences regardless of temperatureregimes. Moreover, shoot primordia were also formed in place⁸oftendrils in cytokinin treated plants even without chlormequatpre-treatment. Vitis vinifera L., grapevine, gibberellic acid, chlormequat, cytokinins, benzyladenine, inflorescence, tendrils     

In Vitro Floral Development of Oilseed Rape (Brassica napus L.): The Effects of pH and Plant Growth Regulators

The effects of various plant growth regulators and that of pHon the in vitro growth and development of young inflorescencesof Brassica napus L. cv. Westar were examined. A cytokinin wasrequired for normal maturation of floral buds, including thecompletion of microsporogenesis, and it stimulated the initiationof additional buds on the inflorescence axis. Benzylaminopurine(BAP) was the most effective of the cytokinins tested. Gibberellicacid (GA₃) and naphthaleneacetic acid (NAA) alone were ineffective.In combination with BAP, both reduced the positive influenceof the cytokinin but GA₃ was more inhibitory than NAA. At alow initial pH (3.9–4.6), the percentage of cultures whichproduced normal buds was significantly higher, especially inthe presence of 10^-7 M or 5 ? 10^-7 M BAP, in comparison to cultureswith a pH of 5.3-6.0, the standard range for plant tissue culture.     

Involvement of Endogenous Gibberellins in the Chilling Requirements of Strawberry (Fragariaxananassa Duch.)

Plants of Fragaria ananassa Duch. cvs Tioga and Fresno werechilled in a cold store at—1°C for 2–8 months,after which they were transferred to short-day (SD) and long-day(LD)) growth chambers. Chilling promoted subsequent vegetative development, as expressedthrough leaf area, petiole length and stolon production, butinhibited the formation of inflorescences. Leaf area and petiolelength responses appeared to be almost saturated by 2 months'chilling. The increase in stolon production and the reductionin inflorescence formation came into full expression with longerperiods of chilling. Application of gibberellin A₃ (GA₃ to plants pre-chilied for2 months had little effect on leaf area or petiole length butpromoted stolon production and retarded the formation of inflorescences.AMO-1618 applied to plants pre-chilled for 4 months antagonizedthe chilling responses. The level of diffusible gibberellin-like substances from crownapices remained low during most of the chilling period but increasedmarkedly after 6–8 months of chilling, when plants approachedspontaneous sprouting in the cold store. Plants pre-chilledfor 2 months had low levels of gibberellin-like substances whichincreased several fold upon transfer to the growth chambers.This increase was somewhat delayed in plants treated with AMO-1618. The role of gibberellins in the responses of strawberry plantsto chilling is discussed.     

Effect of GA3 on the Molecular Mass of Polyuronides in the Cell Walls of Alaska Pea Roots

The role of cell wall matrix polysaccharides in gibberellin-regulatedroot growth is unknown. We examined pectic polysaccharides frompea roots treated with or without gibberellin A₃ (GA₃) in thepresence of ancymidol, an inhibitor of gibberellin biosynthesis.Pectic polymers solubilized by CDTA (trans-l,2-cyclohexanediamine-N,N,N',N'-tetraaceticacid) at 23°C and subjected to gel permeation analysis exhibitedhigh polydispersity with a molecular mass in excess of 500 kDa.Subsequent extraction of cell walls with CDTA at 100°C solubilizedpolymers with an average mol mass of 10 to 40 kDa. Subjectingthe high molecular mass pectic polymers extracted at 23°Cto 70–100°C for 2h generated 10 to 40 kDa fragments,similar in size distribution to those solubilized directly fromcell walls by CDTA solutions at 100°C. Pectic polymers from(GA₃+Anc)-treated roots were of higher average mol mass thanthose from Anc-treated roots in both the elongation zone andin the basal maturation zone. Since (GA₃+Anc)-treated rootselongate more quickly than Anc-treated roots [Tanimoto (1994)Plant Cell Physiol. 35:1019], the slender, GA₃-treated rootsmay produce and deposit highly integrated pectins more rapidlythan the thicker, Anc-treated roots in the elongating or elongatedcell walls. ²Present address: Horticultural Sciences Department, POB 110690IFAS, University of Florida, Gainesville, FL 32611-0690 U.S.A.     

Enhancement of embryogenic culture initiation from tissues of mature sweetgum trees

 Male inflorescences, female inflorescences, and leaves collected from dormant buds of three sweetgum (Liquidambar styraciflua) trees were tested for induction of somatic embryogenesis following treatment with thidiazuron, naphthaleneacetic acid (NAA) or different combinations of the two. Explants were placed into culture either within a few days after collection or following 2 months of storage at –15  °C. Although embryogenic cultures were obtained from all three trees, embryogenesis induction was strongly affected by genotype (source tree), with 100% of the staminate inflorescence explants from one tree producing embryogenic cultures in one experiment. Embryogenesis induction was also influenced by explant type, with staminate inflorescences up to five times more likely to produce an embryogenic culture than female inflorescences. No embryogenic cultures were obtained from leaf explants. While treatment with plant growth regulators was not required for embryogenesis induction from inflorescence explants, culture on medium with NAA alone resulted in the highest production of repetitively embryogenic cultures and cultures producing proembryogenic masses. Dormant buds stored for 2 months at –15  °C were still able to produce embryogenic cultures, although frozen storage decreased this ability by over one-half for staminate inflorescences. Received: 20 January 1999 / Revision received: 18 April 1999 / Accepted: 29 April 1999     

Development of secondary inflorescences and in vitro plantlets from inflorescence cultures of Amaranthus paniculatus

Immature inflorescences of Amaranthus paniculatus were used as explants for in vitro culture studies. When placed on a medium supplemented with 3–6 mg/l kinetin, explants developed into secondary inflorescences. Leaves and shoots developed following culture of inflorescence tissue on media containing 8–15 mg/l kinetin or 5–10 mg/l BAP. These shoots when subcultured on MS medium supplemented with 12 mg/l kinetin + 15% coconut milk, formed roots. These rooted plantlets later flowered in vitro.Abbreviations MS Murashige and Skoog - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - BAP 6-benzylaminopurine - Kn 6-furfurylaminopurine - CM coconut milk     

Effects of Photoperiod, Nitrogen Nutrition and Temperature on Inflorescence Initiation and Development in Onion (Allium cepa L.)

The effects of photoperiod, nitrogen nutrition and temperatureon inflorescence initiation and development in onion cv. Rijnsburgerand cv. Senshyu Semi-globe Yellow were studied in controlledenvironments. Rates of inflorescence initiation were estimatedusing the data for leaf numbers formed prior to flower formationand the rates of leaf initiation. At 9 °C inflorescenceinitiation was accelerated by long photoperiods particularlyfor cv. Rijnsburger where the average time for initiation was86 days in 8 h and 38 days in 20 h photoperiods. Initiationwas as rapid at 12 °C as at 9 °C but was slower at 6°C. A reduction in the nitrate concentration in the nutrientsolution from 0.012 to 0.0018 M greatly accelerated inflorescenceinitiation particularly in photoperiods and temperatures notconducive to rapid initiation. Cv. Senshyu initiated more slowlythan cv. Rijnsburger and was less sensitive to photoperiod andnitrogen level. The development rate of inflorescences afterinitiation was accelerated by long photoperiods and increasesin temperature from 6 to 12 °C but was retarded by the lowernitrogen level. Allium cepa L., onion, flower initiation, inflorescence development, photoperiod, nitrogen nutrition, temperature, vernalization     

Benzyladenine Promotes Flowering in <Emphasis Type="Italic">Doritaenopsis</Emphasis> and <Emphasis Type="Italic">Phalaenopsis</Emphasis> Orchids

Two experiments were performed to determine how application of the cytokinin benzyladenine (BA) influenced flowering in Doritaenopsis and Phalaenopsis orchid clones. In the first experiment, two vegetative orchid clones growing in 15-cm pots were transferred from a 28°C greenhouse that inhibited flowering to a 23°C greenhouse for flower induction (day 0). A foliar spray (0.2 L m⁻²) containing BA at 100, 200, or 400 mg L⁻¹ or 25, 50, or 100 mg L⁻¹ each of BA and gibberellins A₄ + A₇ (BA+GA) was applied on days 0, 7, and 14. Plants treated with BA alone at 200 or 400 mg L⁻¹ had a visible inflorescence 3–9 days earlier and had a mean of 0.7–3.5 more inflorescences and 3–8 more flowers per plant than nontreated plants. The application of BA+GA had no effect on inflorescence number and total flower number at the rates tested. In the second experiment, three orchid clones received a single foliar spray of BA at 200 mg L⁻¹ at six time points relative to time of transfer from 29°C to 23°C (−1, 0, +1, +2, +4, or +6 weeks). A separate group of plants received a BA application at week 0 but was maintained at 29°C. Inflorescence number was greatest in all three orchid clones when plants were treated with BA 1 week after the temperature transfer. Plants that were sprayed with BA and maintained at 29°C did not initiate inflorescences. The promotion of flowering by the application of BA suggests that cytokinins at least partially regulate inflorescence initiation of Doritaenopsis and Phalaenopsis, but its promotion is conditional and BA application cannot completely substitute for an inductive low temperature.     

Effect ofin vivo andin vitro application of the cytokinin N6 -(m-hydroxybenzyl)adenosine on respiration and membrane transport processes in sugar beet

Sugar beet grown in pots was sprayed with N⁶-(m-hydroxybenzyl)adenosine, (mOH)- [9R]BAP, one of the synthetic cytokinins. Root tissue was then examined for respiration and for H⁺-adenosinetriphosphatase activity and both leaf and root tissue served as the object for 6-deoxy-D-glucose and 2-aminoisobutyric acid uptake estimations. Treatment with (mOH)[9R]BAP depressed the uptake of oxygen by the roots of both young and old plants by 17 – 30 % while addition of (mOH)[9R]BAP to the respiring slices decreased it by 10 – 23 %. Uptake of 6-deoxy-D-glucose was mostly diminished byin vivo spraying with the cytokinin (by up to 12 % in leaves and by up to 60 % in roots), as well as by adding it to the experimental vessel (insignificantly in the leaves but by up to 80 % in the roots). The H⁺-ATPase activity was stimulated bothin vivo andin vitro appreciably in young plants but not at all in plants at the end of their vegetation period. Acknowledgement: The work described here was supported by grant No. 501/94/0413 of the Grant Agency of the Czech Republic     

Changes in the Distribution of 14C-Labelled Assimilates in Sugar-beet with Variation of Temperature

Plants were allowed to assimilate ¹⁴CO₂ for 30 min at 5, 15,25, and 35 °C. The changes in ¹⁴C content of a mature expandedleaf (Leaf 4), young apical leaves, and storage root, were sequentiallyfollowed over a subsequent period of 24 h in continuous light.In a second experiment plants were transferred after ¹⁴CO₂ assimilationto temperatures of 10, 18, 26, and 34 °C, and the partitionof ¹⁴C between the ethanol-soluble and ethanol-insoluble fractionsof the roots and leaves was followed over a period of 72 h. The specific activities of the apical leaves and of the storageroot increased to a maximum 2 h after labelling at 25 °C,4 h at 15 and 35 °C, and 6 h at 5 °C suggesting thatthe optimum temperature for translocation of photosynthate wasabout 25 °C. The ¹⁴C partition to ethanol-soluble and ethanol-insoluble fractionsof the roots and leaves was largely attained in. 9 h. Littlerepartition of ¹⁴C assimilate fractions occurred as a resultof temperature change or growth. Root ethanol-insoluble activity,however, did increase significantly over the 72-h period : possiblecauses of this slow incorporation and their relevance to themechanism of sugar storage are discussed.     

Effects of exogenous cytokinins on root formation in pea cuttings

Benzylaminopurine (BAP) or zeatin continuously supplied through the rooting solution to cuttings of pea ( Pisum sativum L. cv. Weibull's Marma), inhibited root formation down to a concentration of 3.10⁻⁹ M . The inhibitory effect of BAP in the concentration range 10⁻⁸–10⁻⁷ M was readily reversible if the cuttings were transferred to solutions without cytokinin after treatment for 1–4 days. A slight increase in the number of roots formed was obtained after treatment with low cytokinin concentrations for 1–2 days. Evidence from microscopic studies of primordia formation indicates that BAP inhibits differentiation of primordia at an early stage in their development. Growth of already formed primordia, or root elongation, was considerably less sensitive to the inhibitory effect of BAP. The results indirectly support the hypothesis that endogenous cytokinins prevent root formation in stems of intact plants and may be of importance for the regulation of rooting in cuttings.     

Inflorescence of grapevine (Vitis vinifera L.): a high ability to distribute its own assimilates

The distribution of carbon (C) into whole grapevine fruiting cuttings was investigated during flower development to determine the relative contribution of inflorescence and leaf photoassimilates in the total C balance and to investigate their partitioning towards other plant organs. A (13)C labelling procedure was used to label C photoassimilates by leaves and inflorescences in grapevine. Investigations were carried out at various stages of flower/berry development, from separated cluster to fruit set, using grapevine fruiting cuttings with four leaves (Vitis vinifera L. cv. Chardonnay). This is the first study reporting that, during its development, (i) the carbon needs of the inflorescence were met by both leaf and inflorescence photosynthesis, and (ii) the inflorescence amazingly participated significantly to the total C balance of grapevine cuttings by redistributing an important part of its own assimilates to other plant organs. With regard to flowering, 29% of C assimilated by the inflorescence remained in the inflorescence, while partitioning towards the stem reached 42% and, as a lower proportion, 15% in leaves, and 14% in roots.     

Reproductive Anatomy of the Grape-vine (Vitis vinifera L.): Origin and Development of the Anlage and its Derivatives

The origin and development of anlagen (undifferentiated primordia),inflorescences, tendrils and flowers in the grape cv. Shirazhas been investigated by scanning electron microscopy. Anlagenarise terminally by bisection of the apex of the so-called latentbud. The axis of the latent bud is continued by the originalapex and anlagen are displaced laterally. Micrographs presentedhere favour the interpretation of the grape-vine shoot as amonopodium. Anlagen formed distal to the 10th node of container grown vinesformed inflorescence primordia when plants were grown at hightemperatures (33°C day-28°C night). At lower temperatures(21°C day, 16°C night or 18°Cday, 13°C night)anlagen formed distal to the 10th node grew into tendril primordia.At basal nodes anlagen gave rise to shoot primordia. Each branchof the highly-divided inflorescence primordium of Shiraz formsfive flower primordia. Flower development is discussed.     

Propagation of Citrus reticulata via in vitro Seed Germination and Shoot Cuttings

Seeds of Citrus reticulata were germinated efficiently when they were sown directly after their extraction from fruits harvested in January, and incubated at constant temperature (25 °C). Seed drying decreased both the percentage of seed germination and the number of seedling per seed. Germination of seeds was better on Murashige and Skoog (MS) medium supplemented with 0.5 mg dm⁻³ benzylaminopurine (BAP) than in a soil. Shoot cuttings obtained from germinated seeds were subcultured on B5 medium supplemented with 1 mg dm⁻³ BAP, 0.5 mg dm⁻³ kinetin (KIN) and 0.5 mg dm⁻³ naphthalene acetic acid (NAA), where shoots grew and multiplied. They were rooted on half strength MS medium supplemented with 0.25 mg dm⁻³ BAP, 0.5 mg dm⁻³ NAA and 1 mg dm⁻³ isobutyric acid (IBA). Rooting under light was better than under dark. Seedlings and shoot cuttings with roots were transferred successfully to the soil after three weeks of acclimatization. This revised version was published online in July 2006 with corrections to the Cover Date.     

Root Zone Temperature Effects on Growth and Nitrate Absorption in Rape (Brassica napus cv. Emerald)

Effects of root temperatures, ranging from 10–35 °C, on growth and nitrate inflow of fodder rape seedlings (cv.Emerald) were examined. These were cultured in solution, withtheir shoots held at 25 ° C. Nitrate inflow (uptake rateper unit root length) was little affected over the temperaturerange 10–30 ° C, although enhanced values were foundat 35 ° C. Nitrate absorption by roots at 10-30 ° Cdepleted solution concentrations to an apparent minimum of approximately6.0 µM NO₃^–. Relative growth rates were highestwith root temperatures of 25 ° C and 30 °C, and thesewere associated with the greatest nitrate depletion rates fromsolution. Root: shoot weight ratios were also greatest at 25°C and 30 °C. At 10 °C and 35 °C a relativelylarge shoot on a small root maintained nitrate inflow in spiteof the plants' slow growth rate. The nitrogen concentrationin the shoots was little affected by root temperature. Slowgrowth at a root temperature of 10 °C was not associatedwith a shortage of nitrogen in the shoots. The principal influenceof temperature appears to be on extension and differentiationof root tissues, possibly through effects on carbohydrate supplyto root meristems.     

Adaptation of Grapevine Flowers to Cold Involves Different Mechanisms Depending on Stress Intensity

Grapevine flower development and fruit set are influenced by cold nights in the vineyard. To investigate the impact of cold stress on carbon metabolism in the inflorescence, we exposed the inflorescences of fruiting cuttings to chilling and freezing temperatures overnight and measured fluctuations in photosynthesis and sugar content. Whatever the temperature, after the stress treatment photosynthesis was modified in the inflorescence, but the nature of the alteration depended on the intensity of the cold stress. At 4°C, photosynthesis in the inflorescence was impaired through non-stomatal limitations, whereas at 0°C it was affected through stomatal limitations. A freezing night (−3°C) severely deregulated photosynthesis in the inflorescence, acting primarily on photosystem II. Cold nights also induced accumulation of sugars. Soluble carbohydrates increased in inflorescences exposed to −3°C, 0°C and 4°C, but starch accumulated only in inflorescences of plants treated at 0 and −3°C. These results suggest that inflorescences are able to cope with cold temperatures by adapting their carbohydrate metabolism using mechanisms that are differentially induced according to stress intensity.     

Concurrent Rates of N2 Fixation, Nitrate and Ammonium Uptake by White Clover in Response to Growth at Different Root Temperatures

Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown for 71 d in flowing nutrient solutions containingN as 10 mmol m_–3 NH₄NO₃, under artificial illumination,with shoots at 20/15°C day/night temperatures and root temperaturereduced decrementally from 20 to 5°C. Root temperatureswere then changed to 3, 7, 9, 11, 13, 17 or 25°C, and theacquisition of N by N₂ fixation, NH₄+ and NO₃^– uptakewas measured over 14 d. Shoot specific growth rates (d. wt)doubled with increasing temperature between 7 and 17°C,whilst root specific growth rates showed little response; shoot:root ratios increased with root temperature, and over time at11°C. Net uptake of total N per plant (N₂ fixation + NH₄++ NO₃^–) over 14 d increased three-fold between 3 and 17°C.The proportion contributed by N₂ fixation decreased with increasingtemperature from 51% at 5°C to 18% at 25°C. Uptake ofNH₄+ as a proportion of NH₄+ + NO₃^– uptake over 14 d variedlittle (55–62%) with root temperature between 3 and 25°C,although it increased with time at most temperatures. Mean ratesof total N uptake per unit shoot f. wt over 14 d changed littlebetween 9 and 25°C, but decreased progressively with temperaturebelow 9°C, due to the decline in the rates of NH₄+ and NO₃^–uptake, even though N₂ fixation increased. The results suggestthat N₂ fixation in the presence of sustained low concentrationsof NH₄+ and NO₄^– is less sensitive to low root temperaturethan are either NH₄+ or NO₃^– uptake systems. White clover, Trifolium repens L. cv. Huia, root temperature, nitrogen fixation, ammonium, nitrate     

Effects of Root Temperature and Form of Nitrogen Nutrition on Nitrate Reductase Activity in Oilseed Rape (Brassica napus L.)

The effect of root temperature and form of inorganic nitrogensupply on in vitro nitrate reductase activity (NRA) was studiedin oilseed rape (Brassica napus L. cv. bien venu). Plants weregrown initially in flowing nutrient solution containing 10 µMNH₄NO₃ and then supplied with either nitrate or ammonium for15 d at root temperatures of 3, 7, 11 or 17 °C. Shoot temperatureregime was similar for all plants; 20/15 °C, day/night.Root NRA was highest when roots were grown at 3 and 7 °C.In laminae and petioles NRA was highest when roots were 11 or17 °C. The plants supplied with ammonium had much lowerlevels of NRA in roots after 5 d than the plants supplied onlywith nitrate. NRA in the laminae of plants supplied with ammoniumwas low relative to that in plants supplied with nitrate onlywhen root temperature was 11 or 17 °C. Values of the apparent activation energy (E_a) of NR, calculatedfrom the Arrhenius equation, in laminae and petioles were differentfrom roots suggesting difference in enzyme conformation. Evidencethat the temperature at which roots were growing affected E_awas equivocal. Oilseed rape, Brassica napus L., activation energy, ammonium, Arrhenius equation, nitrate, root temperature, nitrate reductase