Effects of Daylength on Endogenous Gibberellins in Solanum andigena III. Gibberellin Production by the Leaves

Using an agar diffusion technique, it was found that leaves from potato plants growing under long days produced more gibberellin-like substances than did leaves from plants growing under short days. Short day plants irradiated with red light during the long dark period and harvested during the ensuing light period, contained levels of gibberellin-like substances approximating those found in long day grown plants. Red irradiation during the long dark period also resulted in an increase in gibberellin production in short day plants. Four zones of gibberellin-like activity (A, B, C, D) were separated by thin layer chromatography in extracts from potato leaves. Red light treatment reduced the levels of peak D and brought about a concomitant increase in the levels of peak A.     

Effects of Daylenth on Endogenous Gibberellins in Solanum andigena

When tritiated gibberellin A₁ was fed to intact potato plants growing under different daylength conditions it was converted to a more polar acidic metabolite. The rate of metabolism was the same under both long and short day conditions. Attempts were made to obtain information about the possible sites within the cell where gibberellin metabolism took place.     

Effects of abscisic acid on the levels of endogenous gibberellin-like substances in Solanum andigena

Summary Treatment of young, fully expanded leaves of Solanum andigena with synthetic abscisic acid resulted in marked increases in gibberellin-like substances. Abscisic acid treatment caused increases in the gibberellin content of leaves excised from both short day and long day grown plants.     

Carbon Partitioning in Mature Leaves of Pepper: Effects of Daylength

Grange, R. 1. 1985. Carbon partitioning in mature leaves ofpepper: effects of daylength.—J. exp. Bot. 36: 1749–1759. The partitioning of recently fixed carbon has been examinedin mature pepper leaves grown in 6, 10 or 14 h photoperiodsat different irradiances chosen to give similar radiation integralsand in a 6 h photoperiod at the lowest of these irradiances.The partitioning of carbon into export, starch, sugars and respirationwas followed over the photopenod and the subsequent night ina mature leaf. The maximum export rate during the day (approximately 18 µgC cm^–2 leaf h^–1) was not significantly differentamong the treatments. Net photosynthesis rate was directly relatedto irradiance; the proportion of net photosynthesis exportedduring the day was 33% in 6-h days and 57% in 14-h days. Leafstarch accumulation (as a proportion of net photosynthesis rate)increased slightly when plants were grown in 6-h days. The remobilization of starch and sugars at night allowed exportrates to remain similar over 24 h when plants were grown in10-h or 14-h photoperiods. Leaves grown in 6-h days showed nosignificant changes in export rate during the first few hoursof night but exhausted their starch reserves during the nightand export rates declined. Sucrose and hexose levels decreased at the onset of darkness,but did not fall below 40 µg cm^–2 in plants grownin 10-h or 14-h photoperiods; when this level was reached after3–4 h of darkness, starch breakdown began. In leaves grownin both 6-h treatments, sucrose levels fell below 40 µgcm^–2 when starch reserves were depleted during the nightand the export rate decreased concurrently. The results are discussed in relation to the control of exportand starch metabolism in the leaf. Key words: Pepper, partitioning, daylength     

Endogenous Gibberellins in Aralia cordata

Eight gibberellins (GAs) were identified in extracts of buds of Aralia cordata by full scan GC/MS and by Kovats retention indices. These GAs comprised five GAs on the early-13-hydroxylation pathway [GA₁, GA₁₉, GA₂₀, GA₄₄, and GA₅₃] and three other GAs [GA₄, GA₁₅, and GA₃₇]. The major GAs were GA₁₉ and GA₄₄.     

Gibberellins in Developing Cocoa Leaves

The occurrence of gibberellin-like substances in cocoa has beendemonstrated. Using paper and TLC chromatography and lettucehypocotyl bioassay the gibberellins in three stages of cocoa(Theobroma cacao L.cv. Amelonado) leaf development were compared.The highest activity in the acidic and non-acidic ethylacetatefraction was found in mature leaves with cutinized epidermis.There was a similar pattern of activity level and distributionof active zones after chromatographic separation in young expandingleaves and in leaves which had attained full size but were notyet hardened.     

Identification of Endogenous Gibberellins from Salix pentandra

Gibberellins A₁, A₁₉, A₂₀, and A₂₉ have been identified by sequential high-performance liquid chromatography retention time (Rt) and combined gas chromatography-mass spectrometry (Rt and characteristic mass spectra) from elongating shoots of Salix pentandra L. Gibberellins A₁ and A₁₉ were also detected in purified extracts from male and female flowers (catkins) of S. pentandra.     

Interaction of Daylength and Applied Gibberellins on Stem Growth and Leaf Production in Three Varieties of Celery

Pressman, E. and Negbi, M. 1987. Interaction of daylength andapplied gibberellins on stem growth and leaf production in threevarieties of celery.—J. exp. Bot. 38: 968–971. Exogenous application of gibberellins (GAs) stimulated stemlength. The extent of this stimulation was less in long photoperiods,as long days (LD) or as long nights interrupted by night breaks(NB), than it was in short days (SD). Long photoperiods increasedthe length and erectness of leaves and reduced leaf number.Similar morphological changes were stimulated by applied GAs,which were more effective on plants grown in SD than on thosein LD. It is suggested that long photoperiods cause these morphologicalchanges via the production or metabolism of endogenous GAs,but it is not clear how endogenous GAs interact with the appliedones. Key words: Daylength, gibberellins, stem growth, leaf production, celery     

Endogenous Gibberellins in the Developing Liquid Endosperm of Tea

Changes in the kind and level of endogenous gibberellins (GAs) in the developing liquid endosperm of tea (Camellia sinensis L.) were investigated. Gibberellin A₁ (GA₁), GA₈, GA₁₉, GA₂₀, and GA₄₄ were identified by GC-MS or GC-SIM. Besides these early C-13 hydroxylated GAs, GA₃, iso-GA₃, and GA₃₈ were also identified. Of these GAs, GA₁ and GA₃ were the major gibberellins. The levels of these GAs were at a maximum in the globular embryo stage and then decreased rapidly during embryo maturation.     

Effect of Daylength on Phenol Metabolism in the Leaves of Salvia occidentalis

A method of phenol determination in plant leaves has been developed which is based on the in situ oxidation of these compounds in an atmosphere containing ammonia, followed by difference spectrophotometry. The development of the phenol pattern has been studied in each separate leaf of a Salvia occidentalis plant grown in short and in long days. During the light period the phenol content (mainly chlorogenic acid and isochlorogenic acids) increases in proportion to the length of this period, whereas during the subsequent dark period the phenol content decreases. This decrease does not continue during the second part of a dark period if that period is interrupted by a light break with red light. Instead a small increase is observed. This effect of red light can be reversed with far red light. It is argued that a correlation with flower induction in this short day plant can be construed if it is assumed that the continuous presence of certain o-dihydroxyphenols in the cytoplasm of leaf cells inhibits the synthesis or the transport of a flowering hormone.     

Qualitative and Quantitative Analysis of Endogenous Gibberellins in Onion Plants and Their Effects on Bulb Development

Evidence has been reported that bulb development in onion plants (Allium cepa L.) is controlled by endogenous bulbing and anti-bulbing hormones, and that gibberellin (GA) is a candidate for anti-bulbing hormone (ABH). In this study, we identified a series of C-13-H GAs (GA₁₂, GA₁₅, GA₂₄, GA₉, GA₄, GA₃₄, and 3-epi-GA₄) and a series of C-13-OH GAs (GA₄₄, GA₂₀, GA₁ and GA₈) from the leaf sheaths including the lower part of leaf blades of onion plants (cv. Senshu-Chuko). These results suggested that two independent GA biosynthetic pathways, the early-non-hydroxylation pathway to GA₄ (active GA) and early-13-hydroxylation pathway to GA₁ (active GA), exist in onion plants. It was also suggested that GA₄ and GA₁ have almost the same ability to inhibit bulb development in onion plants induced by treatment with an inhibitor of GA biosynthesis, uniconazole-P. The endogenous levels of GA₁ and GA₄, and their direct precursors, GA₂₀ and GA₉, in leaf blades, leaf sheaths, and roots of 4-week-old bulbing and non-bulbing onion plants were measured by gas chromatography/selected ion monitoring with the corresponding [²H]labeled GAs as internal standards. In most cases, the GA levels in long-day (LD)-grown bulbing onion plants were higher than those of short-day (SD)-grown non-bulbing onion plants, but the GA₁ level in leaf blades of SD-grown onion plants was rather higher than that of LD-grown onion plants. Relationship between the endogenous GAs and bulb development in onion plants is discussed.     

Distribution of Endogenous Gibberellins in Vegetative Shoots of Rice

Levels of endogenous gibberellins in rice seedlings (Oryza sativaL., cv. Nipponbare) were compared between young and old leavesat the 4- and 5-leaf stages. The levels of GA₁, GA₁₉ and GA₅₃were higher in the youngest leaf than in older leaves at the5-leaf stage, but they did not differ significantly betweenthe leaf sheath and the leaf blade. At the 4-leaf stage, thelevel of GA₁, was highest in the third leaf sheaths which containedyoung elongating tissues. These results indicate that gibberellinsare synthesized in young vegetative tissues to promote theirelongation growth. The levels of GA₁ in the youngest leaf sheathsof two cultivars of dwarf rice, Tan-ginbozu and Waito-C, wereapproximately 10% of that in the normal rice at the 5-leaf stage.This result could explain the retardation of shoot elongationin these dwarf cultivars. (Received February 15, 1995; Accepted June 1, 1995)     

Endogenous Gibberellins and Growth of Tobacco Callus Cultures

Tobacco callus grown under a range of conditions for different lengths of time contained various levels of gibberellin-like substances. Culture conditions, viz: light versus darkness and the quantity of cytokinin in the medium, affected the amount of gibberellins found in the tissue. These culture conditions were also important in controlling growth rate of the callus and modified the ability of the tissue to respond to exogenous gibberellins. Furthermore, substances which are known to inhibit gibberellin biosynthesis and also thought to block gibberellin action in some cases, were found to reduce the rate of growth. These data support the idea that endogenous gibberellins may be important in the control of the normal growth of tobacco cells in culture.     

Endogenous Gibberellins in the Xylem Exudate from Apple Trees

In the xylem exudate extracted from the current-year stems of apple (Malus domestica Borkh.), gibberellins A₁₅, A₁₇, A₁₈, A₁₉, A₂₃, A₄₄, and A₅₃ were identified, and 16,17-dihydro-17-hydroxy GA₁₉ was presumed from full-scan mass spectra and Kovats retention indices.     

Endogenous Gibberellins in Floating Plants and Turions of Wolffiella floridana

Endogenous gibberellins from floating plants and in vitro induced turions of Wolffiella floridana (Lemnaceae) were extracted and partially purified. Gibberellin-like activity was detected in two zones of the chromatogram corresponding to Rf 0-0.1 and Rf 0.4-0.5 by dwarf pea bioassay. The active compounds in the two zones have been referred to in this paper as factor I and factor II respectively. There were quantitative differences in the gibberellin-like substances of floating plants and turions. The floating plants contained more of factor I but less of factor II as compared to the turions. The chromatographic behavior of factor I was similar to either gibberellin A₁ and A₃ while the identity of factor II was uncertain.     

Endogenous Gibberellins and Shoot Growth and Development in Brassica napus

Greenhouse-grown oilseed rape (Brassica napus, annual Canola variety `Westar') plants were harvested at six dates from the vegetative phase until the early pod (silique)-fill/late flowering stage. Endogenous gibberellin (GA)-like substances were extracted from stems, purified, and chromatographed on silica gel partition columns prior to bioassay in serial dilution using the `Tan-ginbozu' dwarf rice microdrop assay. The concentrations of total endogenous GA-like substances were low during vegetative stages (1 nanogram GA₃ equivalents/gram dry weight), and rose 300-fold by the time of floral initiation. After floral initiation the concentration of GA-like substances fell, then rose again during bolting to maximal levels during the early pod-fill stage (940 nanograms per gram dry weight). The qualitative profiles of GA-like substances varied across harvests, with higher proportions of a GA₁-like substance at the early pod-fill stage. In a second study stems were similarly harvested at eight dates and the concentrations of endogenous GA₁, the principal bioactive native GA of oilseed rape, were determined by gas chromatography-selected ion monitoring using [17,17-²H]GA₁ as a quantitative internal standard. The concentration of GA₁ increased at about the time of floral initiation and then subsequently fell, thus confirming the pattern noted above for total GA-like substances. The exogenous application of paclobutrazol (PP333), a persistent triazole plant growth regulator (PGR) which blocks GA biosynthesis, or another triazole, triapenthenol (RSW0411), prevented flowering as well as bolting; plants remained at the vegetative rosette stage. These results imply a causal role for endogenous GA, in the control of bolting, which normally precedes anthesis. Further, the rise in the concentration of total endogenous GA-like substances, including GA₁, which was associated with floral initiation, and the prevention of visable floral development by the triazole PGRs, also indicates a role for endogenous GAs in the regulation of flowering in B. napus.     

Key Role for Endogenous Gibberellins in the Control of Seed Germination

The stimulative action of applied gibberellins (GA) on seedgermination has been reported for a large number of speciesin the past three decades. Applied GA often replaces the needfor environmental stimuli like specific temperature pretreatmentor light. Therefore, it has been suggested that endogenous GAsare essential intermediates in the stimulation of germination.Endogenous GAs have been identified in seeds of a limited numberof species, but most of the evidence for a regulatory role isentirely circumstantial. The use of isogenic mutants with lesionsin the GA biosynthesis has presented direct evidence of a keyrole for endogenous GAs in the regulation of germination. GAdeficiency absolutely prevents germination in seeds of Arabidopsisthaliana and tomato. Two different mechanisms of action exist The first one involves hydrolysis of reserve food. In seedsof tomato a factor, probably GA, diffuses prior to germinationfrom embryo to endosperm where it induces hydrolysis of gaJactomannan-richcell walls that are part of the mechanical resistance to theprotrusion of the radicle. A second mechanism of GA action consistsof a direct effect on the growth potential of the embryo. InArabidopsis the stimulation of germination by light dependson the ability of the seeds to synthesize GA, but light alsoenhances the sensitivity of the seeds to GA. Dry storage andpre-incubation at 2°C also increased the responsivenessof Arabidopsis seeds to GA     

Effects of a Plant-Growth Regulat or, Prohexadione-Calcium (BX-112), on the Endogenous Levels of Gibberellins in Rice

The effects of the plant-growth regulator, prohexadione-calcium,on the levels of the endogenous gibberellins in rice shootswere measured by GC-SIM using ²H-labeled gibberellins as internalstandards. The compound was applied at the 4-leaf stage andshoots were harvested 5 and 12 days after treatment. Plant lengthwas reduced to 78% and 66%, respectively, relative to controlby application of the compound at 1 and 30 mg m^–2, whenplant length was measured 12 days after treatment. The levelof GA, was reduced to 36% and 18%, respectively, relative tocontrol in the treated plants. The levels of GA₁₉and GA₂₀ increasedbut that of GA₄₄ was reduced in the treated plants. The levelof GA₅₃ was unchanged. These results suggest that primary modeof action of the compound in vivo is the inhibition of the 3ß-hydroxylationof GA₂₀ to GA₁ and further support the hypothesis that GA₁ notGA₁₉ nor GA₂₀ is active in promoting shoot elongation in rice. ³Present address: Frontier Research Program, RIKEN, Wakoshi,Saitama, 351-01 Japan.     

Quantitative Analysis of Endogenous Gibberellins in Normal and Dwarf Cultivars of Rice

Endogenous levels of gibberellins in shoots and ears of twodwarf rice (Oryza sativa L.) cultivars, Tan-ginbozu (dx mutant)and Waito-C (dy mutant), were analyzed and compared with thoseof normal rice cultivar, Nihonbare. The endogenous levels of13-hydroxylated gibberellins in Tan-ginbozu were much lowerthan those in Nihonbare. In Waito-C, the levels of GA₁₉ andGA₂₀ in the shoots were higher but that of GA₁ was lower thanthe levels of these gibberellins in Nihonbare. These resultssupport the hypothesis that the dy gene controls the 3ß-hydroxylationof GA₂₀ to GA₁ while the dx gene controls a much earlier stepin the gibberellin biosynthesis. Our results indicate that GA₁is the active gibberellin that regulates the vegetative growthof rice. The endogenous levels of GA₄ in the ears of the twodwarf cultivars of rice were higher than the level of GA₄ inthe ears of the normal cultivar, Nihonbare suggesting that thebiosynthesis of gibberellin is not blocked in the anthers ofthe dwarf rice. (Received April 27, 1989; Accepted July 12, 1989)     

Gibberellins and heterosis in maize : I. Endogenous gibberellin-like substances

Under controlled environment and/or field conditions, vegetative growth (height, internode length, leaf area, shoot dry weight, grain yield) was greater in an F₁ maize hybrid than in either parental inbred. Endogenous gibberellin (GA)-like substances in apical meristem cylinders were also higher in the hybrid than in either inbred, both on a per plant and per gram dry weight basis. There were no apparent qualitative differences in GA-like substances, however. Levels of GA-like substances in all genotypes were highest prior to tassel initiation. Chromatographic comparisons of the GA-like substances and authentic standards of GA native to maize on gradient-eluted SiO₂ partition and reverse-phase C₁₈ high-pressure liquid chromatography columns are described. No consistent differences in abscisic acid levels of the three genotypes were observed. This correlation of heterosis for endogenous GA-like substances with heterosis for growth suggests that amounts of endogenous GA may be related to hybrid vigor in maize.