Burst Potential Characterisation by Capacity for Nucleotide Accumulation in Rhododendron Catawbiense Apical Buds

Rhododendron catawbiense cv. Album propagated in vitro were transferred ex vitro and grown in a greenhouse, under long or short days. Under long days, the rhythmic growth led to an acrotonous development. In contrast, under short days, the upper buds were unable to burst, allowing basitony. In both photoperiodic conditions, the apical buds were sampled at different stages of the experiment. Growth capacities of the isolated buds were estimated by measuring their abilities to increase and diversify their non-adenylic nucleotide pool (NTP) after supplying adenosine as a precursor. Under long days, during the growth pause, the apical buds were able to increase and diversify their NTP pool. Under short days, adenosine was used to produce important quantities of ATP, while NTP pool increase became weaker. Nevertheless, during this long growth pause, apical bud tissues retained capacities to increase their NTP pool until the basal shoots developed.     

Induction and floral determination in the terminal bud of Nicotiana tabacum L. cv. Maryland Mammoth,a short-day plant

Floral determination in the terminal bud of the short-day plant Nicotiana tabacum cv. Maryland Mammoth has been investigated. Plants grown continuously in short days flowered after producing 31.4±1.6 (SD) nodes while plants grown continuously in long days did not flower and produced 172.5±9.5 nodes after one year. At various ages, expressed as number of leaves that were at least 1.0 cm in length above the most basal 10-cm leaf, one of three treatments was performed on plants grown from seed in short days: 1) whole plants were shifted from short days to long days, 2) the terminal bud was removed and then rooted and grown in long days, and 3) the terminal bud was removed and then rooted and grown in short days. Whole plants flowered only when shifted from short days to long days at age 15 or later. Only rooted terminal buds from plants at age 15 or older produced plants that flowered when grown in long days. Only terminal buds from plants at age 15 or older that were rooted and grown in short days produced the same number of nodes as they would have produced in their original locations while buds from younger plants produced more nodes than they would have in their original locations. Thus, determination for floral development in the terminal bud, as assayed by rooting, is simultaneous with the commitment to flowering as assayed by shifting whole plants to non-inductive conditions.Abbreviations LD long day(s) - SD short day(s) - DN dayneutral     

Phénolamides et induction florale de Cichorium intybus dans différentes conditions de culture en serre ou in vitro

Phenolamides and floral induction of Cichorium intybus in different conditions of culture in glass-room or in vitro. Three complexes between phenols and amines (phenolamides) have been found in Cichorium intybus L., a plant with an absolute requirement of vernalisation followed by long days for flowering. Upon hydrolysis, these complexes (A, B and C) liberate aromatic amines whose exact identification is in progress, but which are closely related to dopamine, tyramine and serotonin, respectively. In a first series of experiments, phenolamides were studied in the buds of plants grown in the greenhouse under varying conditions. Only buds from plants which flower in long days contained large amounts of these compounds. Much smaller amounts were found in buds at the end of vernalisation (at 2–4°C) before long-day treatment as well as in buds kept in the vegetative state after vernalisation by being grown in short days (8 h light) or in total darkness. In a second series of experiments, phenolamides were studied in bud-forming calli induced in vitro on explants of tuberised root. After sixteen days of culture in continuous light, large quantities of phenolamide were found in the buds and calli of the upper part of the explant, while the lower part which never produces buds contained much less. Buds formed under continuous light produce inflorescences in approximately one month. Various other culture conditions make it possible to maintain the explants in the vegetative state. This can be obtained by short-day conditions, or otherwise under continuous illumination by decreasing the sugar or increasing the NAA levels in the medium. After 13 days of culture, the phenolamide levels were much lower under all of these conditions, than under conditions favourable to floral induction. Compound C is absent or present in trace amounts in vegetative buds. The significance of the differences observed between floral and vegetative buds is supported by the sensitivity of the analytical techniques used. The accumulation of phenolamides in tissues of Cichorium intybus appears to be closely linked to floral induction. Under continuous light it begins very early in young buds and even in the calli that bear these buds.     

Effect of Photoperiod and Chlorogenic Acid on Morphogenesis in Leaf Discs of Streptocarpus Nobilis

Leaf discs from vegetative plants greatly increase their phenolic content when cultivated in vitro. Under long days the values remained constant, and were higher when compared with short days cultures. Under short days total phenolics decreased after 10 d, corresponding to the induction and expression of in vitro flowering. The effect of photoperiod and chlorogenic acid (0.01 mM) on leaf discs cultured from induced and non-induced plants, were analyzed regarding the neo-formation of roots, as well as vegetative and flower buds. Chlorogenic acid enhances the regeneration of roots in all treatments tested, with the highest stimulation on induced leaf discs cultivated in short days. The flowering was not affected by chlorogenic acid, but an inhibitory effect was observed on the neo-formation of vegetative buds in non-induced explants maintained in short days. Vegetative buds were reduced by 50% in flower-induced leaf discs cultivated under short days.     

Effect of growth substances on flowering and sex expression in isolated apical buds of Spinacia oleracea

Apical buds of Spinacia oleracea L. cv. Matador were isolated from 7-day-old vegetative seedlings and grown in sterile culture under inductive long, or non-inductive short photoperiods. Flowering of isolated apices was inducible in long days in approximately 75% of the plants, and in short days by gibberellin treatment (about 40%) or by raising the temperature to 30–32°C (13%). In long days the percentage of flowering was further increased by gibberellin treatment (up to 90%), while it was unaffected by abscisic acid and was strongly decreased by Amo 1618 (55%). In long days the ratio of male to female plants was near 1. The percentage of female plants in long days was increased by gibberellins, and the percentage of male ones decreased by kinetin; as a consequence, the ratio of male to female plants was lowered to about 0.50 in both cases. Abscisic acid and Amo 1618 had the opposite effect, probably because they decreased the flowering in female plants, so that the sex ratio was shifted to 2.6 and 6.8, respectively. Simultaneous treatment with GA₃ reversed the effect of abscisic acid on the sex ratio, but the reversal of the shift to maleness induced by Amo 1618 was only partial. In short days, gibberellins also stimulated the flowering in female plants more than in male. However, when the flowering was induced by higher temperature, most flowering plants were male and kinetin increased their percentage further. The above results have been discussed in terms of different requirements for flowering in male and female plants.     

Effects of diurnal and bidiurnal photoperiodic treatments on mitosis in Pharbitis

Abstract

Photoperiodic effect on mitotic activity of buds from dwarf Pharbitis has been analyzed. No significant differences in mitotic activity were found in plants grown under long days or diurnal (24 h) light break photoperiodic treatments. Differences in both mitotic activity and flowering were seen in plants subjected to diurnal short days, bidiurnal (48 h) short days, or bidiurnal short days with light breaks. An elevation of mitotic activity occurs in plants grown in bidiurnal photoperiodic treatments compared to diurnal treatments. The differences in mitotic activity of buds, both vegetative and floral, seem to indicate that both phytochrome and light effect on an endogenous rhythm influence meristematic activity. Also, the extended dark period of a bidiurnal short day enhances both mitosis and flowering.     

Induction of Cold Acclimation in Cornus stolonifera Michx

A warm (20 to 15 Celsius day or night) preconditioning treatment enhanced cold acclimation of Cornus stolonifera bark under short-day conditions when plants were preconditioned for at least 4 weeks. Warm preconditioning inhibited the acclimation of plants subjected to long photoperiods. Removing leaves from plants exposed to low temperatures and short days inhibited acclimation. Removal of buds did not affect acclimation. Plants did not acclimate unless they were exposed to at least 4 weeks of short photoperiods prior to defoliation. Plants began to acclimate to cold at the time of growth cessation but not before. When half of the leaves were removed from plants, the defoliated and foliated branches both acclimated as well as branches on completely foliated plants. Girdling the phloem between foliated and defoliated branches prevented acclimation of the latter regardless of the position of the girdle in relation to the root system and the defoliated branch. When all of the leaves of plants were covered with aluminum foil to exclude light after 0 or 4 weeks of exposure to short days, the results resembled a defoliation study, i.e., plants with leaves covered at the start of the experiment failed to acclimate, and those covered after 4 weeks acclimated to some extent but less than uncovered control plants. Under longday conditions plants with all leaves covered failed to acclimate, and plants with none or half of their leaves covered acclimated equally and to a limited extent. Under short-day conditions, however, the covered branches of partially covered plants acclimated more than their uncovered counterparts or branches of totally uncovered plants.     

Autophagy regulated by day length determines the number of fertile florets in wheat

SUMMARY: The wheat spikelet meristem differentiates into up to 12 floret primordia, but many of them fail to reach the fertile floret stage at anthesis. We combined microarray, biochemical and anatomical studies to investigate floret development in wheat plants grown in the field under short or long days (short days extended with low-fluence light) after all the spikelets had already differentiated. Long days accelerated spike and floret development and greening, and the expression of genes involved in photosynthesis, photoprotection and carbohydrate metabolism. These changes started while the spike was in the light-depleted environment created by the surrounding leaf sheaths. Cell division ceased in the tissues of distal florets, which interrupted their normal developmental progression and initiated autophagy, thus decreasing the number of fertile florets at anthesis. A massive decrease in the expression of genes involved in cell proliferation, a decrease in soluble carbohydrate levels, and an increase in the expression of genes involved in programmed cell death accompanied anatomical signs of cell death, and these effects were stronger under long days. We propose a model in which developmentally generated sugar starvation triggers floret autophagy, and long days intensify these processes due to the increased carbohydrate consumption caused by the accelerated plant development.     

STUDIES ON THE FLORAL HISTOGENESIS AND PHYSIOLOGY OF PERILLA. II. FLORAL INDUCTION IN CULTURED APICAL BUDS OF P. FRUTESCENS

Raghavan , V., and W. P. Jacobs . (Princeton U., Princeton, N. J.) Studies on the floral histogenesis and physiology of Perilla. II. Floral induction in cultured apical buds of P. frutescens. Amer. Jour. Bot. 48(9): 751–760. Illus. 1961.—The morphological and histological changes induced in apical buds and explants of P. frutescens (L.) Britt. var. ‘Tall Late’ in short days and long days when cultured in White's medium have been followed. When photoinduced in culture, apical buds showed visible signs of changes in 30.9 days, and produced normal flowers in 81.6 days. Apical buds in LD showed similar transformations at the apices, but with continued LD treatment, they elongated to form sterile structures, superficially resembling Selaginella cones. The normal flowers formed in culture were similar to those formed on the intact plant, while the individual florets of the LD-cone differentiated only the non-sporogenous tissues in them. A less pronounced sequence of changes resulted when apical buds stripped of their older pairs of apical leaves were LD- or SD-treated. When explants with the 1st pair of unfolded leaves or with the 1st and 2nd pairs of unfolded leaves were photoinduced in vitro, the responses were relatively fast. However, explants with the 1st and 2nd pairs of unfolded leaves in LD remained entirely vegetative. When unfolded leaves were implanted in the same medium separated from the buds and both were photoinduced or given LD, the buds formed the typical 1st signs, but did not differentiate into normal flowers. This inhibition of flowering resulted in the formation of sterile cones, consisting of florets with non-sporogenous tissues only. The results have suggested the possibility of the sterile cone-like structures being an intermediate stage in the flowering of Perilla. The role of a possible inhibitor produced by mature leaves of SD plants in LD is discussed.     

Metabolism and Transport of [2-14C]({+/-}) Jasmonic Acid in the Potato Plant

Metabolism and transport of [2-¹⁴C](±) jasmonic acid(JA) were studied using 2-week-old potato plants. Plants grownunder tuber inducing conditions (short days) and non-inducingconditions (long days) were assayed 1, 5, 10, 15, 20, and 25days after substance application. The incorporated [2-¹⁴C](±)JAwas metabolized to tuberonic acid glucoside (TAG) within 2 weeks.The radioactivity of the ethanol extract from each plant partwas measured. More than half of the total radioactivity wasstill associated with the treated leaves up to 25 days afterthe application of [2-¹⁴C](±)JA. In the other parts ofthe plants, the upper leaves contained the most total radioactivity,followed by the stems and lower leaves. Under long days no tuberswere produced, and the radioactivity of the stolons was observed.In contrast, under short days tuber were produced, and the radioactivitieswere present in stolons and tubers. Flower buds and flowerswere produced more under long days and accumulated high radioactivity.It is concluded from the combined data that JA is metabolizedto TAG and transported to all parts of the plant. A high accumulationof TAG in tubers and flower buds may induce the formation oftubers and flower buds. (Received January 22, 1996; Accepted April 15, 1996)     

Evergreen Foliage Contributions to the Spring Growth of Taxus

Taxus media cv. Hicksii plants were grown one season under a low and high level of nitrogen fertilization. Before growth in the spring the plants were divided into two groups, one of which was defoliated and the other left intact. The growth and spring utilization of the nitrogen and carbohydrate reserves of defoliated plants were compared to the intact plants 0, 2, 4 and 6 weeks after growth started in the spring. The plants were separated into buds (all new growth), roots and stems and analyzed for changes in total nitrogen, basic and non-basic amino acids, hemicelluloses, soluble sugars, organic acids and chlorophyll. The older evergreen needles from plants grown under low nitrogen levels contain 20 % of the carbohydrate and 24% of the nitrogen used in spring growth. The needles from plants grown under high nitrogen levels contained 56% of the carbohydrate and 49% of the nitrogen used in spring growth. Removal of the old needles before spring growth removed this nitrogen and carbohydrate reserve and reduced the total plant chlorophyll content after 6 weeks of growth to 50% of that found in intact plants, with the result that defoliated plants did not show a growth response to nitrogen. Amino acids accumulated in the stems and buds of defoliated plants as carbohydrates became limiting. The defoliated plants removed 25% more available carbohydrates from the roots and stems than intact plants and their buds contained 50% less available carbohydrates. Plants without old needles showed similar growth rates under low and high nitrogen regimes and produced 33% of the dry weight of intact plants grown under high nitrogen levels and 66% of the dry weight of intact plants grown under low nitrogen levels. The old needles of taxus plants contain substantial amounts of reserve nitrogen and carbohydrate and these needles greatly influence the extent and rapidness of growth in the spring. When the needles are removed, the other tissues can supply an adequate amount of nitrogen but the carbohydrate supply becomes limiting for spring growth.     

Efficient regeneration of plants independent of exogeneous growth regulators in bell pepper (Capsicum annumm L.)

Summary Organogenesis of shoots of bell pepper (Capsicum annuum L.) was achieved in fourteen cultivars on Murashige and Skoog's medium (MS medium) supplemented only with 0.4% (w/v) Gellan gum (pH 5.8). Mature seeds of cv. Shinsakigake-2 were sown on filter paper that had been wetted with sterilized water and precultured for zero to five days in under 16 hr of light per day at 25 °C. Explants, consisting of the proximal part of the hypocotyl and the radicle, were excised from the seeds and formed adventitious buds around the cut surfaces of elongated hypocotyls after four weeks of culture. When explants were subcultured on MS medium, 57% of the explants that had produced adventitious buds extended shoots after an additional three weeks of culture. Shoots were rooted on MS medium after two further weeks of culture. Chromosome numbers of all 30 regenerated plants that weexamined were normal (2n=24). The morphology of the mature plants was also normal and they set normally shaped fruits with mature seeds. Regenerated whole plants were also obtained in the case of 13 other cultivars by applying this simple procedure.Abbreviations MS Murashige and Skoog     

Direct shoot regeneration from immature inflorescence cultures of <Emphasis Type="Italic">Chlorophytum arundinaceum</Emphasis> and <Emphasis Type="Italic">Chlorophytum borivilianum</Emphasis>

Direct shoot regeneration was achieved from immature inflorescence explants of Chlorophytum arundinaceum and C. borivilianum on half-strength Murashige & Skoog (MS) medium supplemented with 3.0 mg L⁻¹ BA, 150 mg L⁻¹ Ads, 0.1 mg L⁻¹ NAA and 3% (w/v) sucrose under a 16-h photoperiod. The shoot buds developed within 2–3 weeks of culture. High frequency of shoot bud regeneration was achieved when cultured on similar medium in subsequent subcultures. The apex portion (Type I) of the inflorescence produced more shoot buds as compared to the middle ones (type II). More than 75% of the terminal segment explants produced shoot buds within 4-week of culture. Response of basal portion (Type III) was negative for shoot bud initiation. Shoots rooted on half-strength basal MS medium supplemented with half-strength MS medium, 0.1 mg L⁻¹ IAA and 2% (w/v) sucrose. Micropropagated plantlets were hardened in the green house and successfully established in the soil where 90% of the plants survived. This protocol would be useful for commercial micropropagation and genetic improvement prograrmme.     

In vitro Organogenesis in Explants from Different Cultivars of Begonia X hiemalis

Petiole explants from 17 cultivars of Begonia X hiemalis were grown on a basal agar medium with different combinations of NAA and BA as well as on media lacking microelements or vitamins. The stock plants were kept either under short days (7–8 h of light perday) at 15°C or under long days (15–16 h of light) at 18–21°C. The day length during the in vitro culture was 20 h of light and the temperature 21°C. Explants from short-day treated stock plants did not show any differentiation. In explants from long-day treated stock plants, the percentage of explants with shoot, root and with both shoot and root initiation were recorded after 55 days. Explants forming both shoots and roots were transferred to soil, and plantlet formation was observed after another 55 days. The percentage of explants with organ and plantlet formation differed between cultivars. With increasing NAA and decreasing BA concentrations, the percentage of explants forming only roots increased, whereas the percentage of explants with only shoots decreased. Plantlet formation was most frequent in explants from NAA: BA ratios of 2: 1 and 10: 1, and a variation was found between different cultivars. When the vitamin fraction was not added to the medium, this did not influence formation of shoots, roots and plantlets. When the microelements were omitted. shoots, roots and callus were formed, but no plantlets.     

Environmental control and evidence for predetermination of pollen embryogenesis inNicotiana tabacum pollen

Summary The effect of daylenght and temperature for the donor plants (Nicotiana tabacum var. Badischer Burley) on the formation of pollen competent for embryogenesis (P-pollen) by the three possible routes (during normal flower developmentin situ (pollen dimorphism), during cold-treatment of excised flower buds, in cultured anthers) was studied. In all three routes, P-pollen frequency (premitotic pollen, before 1. sporophytic division, PPF) was affected in essentially the same way. At 24 °C and long days, PPF was low and short days had only a slightly increasing effect. At 18 °C and long days, PPF was higher and short days further increased it. Correlated with PPF under the different growth regimes was the percentage of units with more than one vegetative-type nucleus (normal embryos + abortive embryos + multinucleate pollen) in 3 weeks old anther cultures. Under greenhouse conditions, PPF was generally higher than at 24° in growth rooms and showed a maximum in the winter months. Plant age did not affect PPF. These results give further evidence that pollen embryogenesis is predetermined before excision and culture of the pollen or anthers.     

Environmental control of cold hardiness in woody plants

The development of cold hardiness in 2 woody plant species (Acer negundo and Viburnum plicatum tomentosum) was shown to be independent of the induction of bud dormancy. Substantial hardiness levels were obtained under controlled conditions with long days and certain low temperatures—without dormancy development as a prerequisite.

Low temperatures given during the dark period with long days induced hardiness to a level not significantly different from that of short days. Giving plants continuous 10° temperatures under long days forced plants to harden as if they were under short days, even though they were not dormant.

Development of hardiness was shown to be a photoperiodic response. Increasing weeks of short days, followed by a low temperature hardening period in darkness, brought about a progressive increase in hardiness. The short day stimulus could be reversed by long days. Following 6 weeks of short days, the rate of hardening in darkness at 5° was over twice that of plants previously exposed to long days.

     

Morpho-histological characterization and direct shoot organogenesis in two types of explants from <Emphasis Type="Italic">Bacopa monnieri</Emphasis> on unsupplemented basal medium

In the present study, high frequency regeneration has been obtained via de novo direct shoot organogenesis from leaf and internode explants in Murashige and Skoog (MS) basal medium without any phytohormone supplementation in Bacopa monnieri, an indigenous traditionally used medicinal herb. Leaves and internodes from different positions were excised from 4-weeks-old in vitro propagated B. monnieri plants and cultured on MS basal medium supplemented with 3% (w/v) sucrose and 0.75% (w/v) agar for 4 weeks. The induction of de novo shoot buds was observed at petiolar cut edges of leaf and both proximal and distal cut ends of internode explants within 10–15 days of culture. The first histological changes could be observed after 4–5 days, with meristematic activity of vascular bundles. Proliferation of epidermal cells gave rise to dome-shaped protuberances followed by shoot apical meristems formation and their vascular connections with explant tissues within 2 weeks of culture. However, a basipetal gradient of shoot regeneration from both types of explants collected along the branch axis was noticed after 4 weeks of culture. Leaf and internode explants near the basal region exhibited significantly higher number of shoot buds and micro shoots (8.8/leaf explant and 15/internode explant). Microshoots (7–12 micro shoots/leaf or internode explants) elongated (shoot length 8–9 cm) within 8 weeks on phytohormone free MS medium. Excised micro shoots rooted (100%) in hormone free MS medium within two weeks of culture. Rooted plants were then acclimatized and transferred to field with 95% survival. This protocol may be used for micropropagation, genetic transformation as well as a model system for evaluation of changes associated with acquisition of competence of differentiated cells in phytohormone free medium.     

Induction of embryogenic pollen grains in situ and subsequent in vitro pollen embryogenesis in Nicotiana tabacum by treatments of the pollen donor plants with feminizing agents

Tobacco plants ( Nicotiana tabacum L., var. Badischer Burley) were treated with chemicals (sprays and soil drenches) known to affect sex expression in other species. Their effect was tested on sex balance, pollen sterility, embryogenic pollen grain (P-grain) formation in situ, and on pollen plant formation in anther and pollen cultures after anther preculture. Napthalene acetic acid (NAA) increased the length of pistils and stamens and shifted sex balance towards femaleness when the plants were raised in long or short days at 24 or 15°C. In parallel, pollen sterility, P-grain frequency in situ and pollen plant production from anther and pollen cultures were increased by NAA. Alar 85 redueed the length of pistils and stamens and shifted sex balance towards femaleness when the plants were raised in long days at 24°C, but shifted it towards maleness in short days and/or at 15°C. In parallel, pollen sterility, P-grain frequency in situ, and pollen plant production in vitro were increased when plants in long days at 24°C were treated with Alar 85, but decreased when plants in short days and/or at 15°C were treated. Ethrel, Cycocel, and GA₃ applied in a similar manner, were ineffective. Water sprays and nitrogen starvation shifted sex balance towards femaleness in long days at 15°C and increased pollen sterility, P-grain frequency in situ and pollen plant production in vitro. At 24°C, water sprays and nitrogen starvation had no effect.     

Reduction of mineral nutrient availability accelerates flowering of Arabidopsis thaliana

The time of flowering is regulated by various environmental cues, and in some plant species, it is known to be affected by abiotic stresses. We investigated the effect of nutrient stress caused by an abrupt reduction of mineral nutrition on flowering of Arabidopsis thaliana. We used a hydroponic culture system that enabled us to precisely control nutrient levels. When plants were grown in full-strength nutrient solution for several weeks and then transferred to a diluted medium, the time from sowing to bud appearance was significantly shortened. This acceleration of flowering was more pronounced in short days than in long days, and stronger in the ecotype Landsberg erecta than in Columbia and San Feliu-2. The response was also affected by the age of plants at the beginning of nutrient stress and by the concentration of the diluted medium: earlier treatment and more diluted solutions strengthened the effect. Flowering was affected by nutrient stress, not by a change in the osmotic potential of the medium: addition of mannitol to a 1000-fold diluted solution had no effect on the promotion of flowering. When 3-week-old Landsberg erecta plants were exposed to 1000-fold diluted nutrient solution in an 8-h day length, flower bud appearance was strongly and reproducibly advanced by 10.8–12.8 d compared with control plants (which developed buds 41.1–46.2 d after sowing). This treatment can serve as an optimized protocol for future studies concerning physiological, molecular and ecological aspects of flower induction by nutrient stress in A. thaliana.     

Changes in the Protein Composition of the Shoot Apical Bud of Sinapis alba in Transition to Flowering

Vegetative plants of Sinapis alba L. grown in short days were induced to flower by expsoure to one or continuous long days. In both inductive conditions, the first flowers were initiated about 60 h after the start of the treatment. Soluble protein extracts were prepared from apical buds and just-expanded leaves of both vegetative and induced plants. Rabbit antisera were prepared using extracts from vegetative and reproductive buds. Immunodiffusion tests were performed. Analysis of the precipitin bands indicated that: (1) one antigenic protein was present in the vegetative buds and disappeared from the buds of induced plants between 96 and 240 h after the start of the inductive treatment; (2) the concentration of a another antigenic protein increased in buds of induced plants 30 h after the start of the inductive treatment; (3) the concentration of a third antigenic proteín increased in buds of induced plants at 96 h.