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Forest slashing and burning is a key characteristic of shifting cultivation. Its intensification is a major anthropogenic cause of deforestation, as it reduces forest resilience. We analyzed the reforestation process in the regenerating shifting cultivation lands in India's Western Ghats, a megadiversity hotspot. An actinorhizal shrub, Elaeagnus conferta, was associated with the regenerating thickets' higher density and higher species diversity. Its presence increased the thicket density by >2.8‐fold and the species diversity by >2.5‐fold; these thickets showed >1.5‐fold higher Shannon's diversity index than those without it. Moreover, the thickets containing E. conferta showed >7‐fold more multi‐species seedlings. Liquid chromatography‐mass spectrometry analysis showed that rhizosphere soils of E. conferta containing thickets had >10‐fold higher gibberellic acid (GA3) concentrations than the E. conferta‐deplete thickets. When E. conferta was potted separately, its root nodules, roots, and rhizosphere soil showed about 3.6, 2.0, and 0.4 μg/g GA3, respectively. These E. conferta root and rhizosphere soil GA3 concentrations were >10‐fold higher than those shown by other co‐occurring species. These elevated GA3 levels were likely due to E. conferta's association with the rhizosymbiont Frankia elaeagni. Frankia elaeagni's GA3 synthesis may promote plant recruitment by stimulating seed germination and explain why we measured higher seedling density and plant diversity in E. conferta containing thickets. We hypothesize that E. conferta plays a two‐stage pioneering role in the reforestation process by providing GA3 to facilitate seed germination and providing nitrogen for the developing plantlets. We recommend the inclusion of E. conferta in Western Ghats' reforestation programs. [ABSTRACT FROM AUTHOR]

Intensive breeding programmes have been carried out to obtain high‐quality seedless grape cultivars. Seedless grape cultivars were used as pollinizer parents, but the number of hybrid seeds and the viability of the seed obtained could differ greatly. In this study, carried out over 3 years, the results obtained from crossing with some pollinizer cultivars belonging to different Vitis species were compared. Maternal cultivars that do not need emasculation (male sterile) and emasculated cultivars were also compared. Evaluations were based on the total number of hybrid seeds and the proportion of viable seeds. In addition, the effects of various treatments on the rates of germination of the hybrid seed were compared. Although the female parents (with female flower structure) produced more seed than did hermaphrodite mothers in 2019, different results were obtained in cross‐breeding studies in 2018 and 2020. Cold stratification was very effective in increasing germination by breaking dormancy of the hybrid seed. In addition, after treatment of cold moist storage (cold stratification), keeping the seed in distilled water overnight before planting increased germination. Although large numbers of seeds were produced by the genotype 86/1 and the cultivar 'Beyaz Çavuş', both of which do not require emasculation, many of these seeds did not germinate. Crosses with the cultivar 'Red Globe' as the maternal parent produced large numbers of viable seeds and high germination rates. [ABSTRACT FROM AUTHOR]

Salinity is one of the major abiotic stresses that limit productivity of pulse crops all over the world. Seed priming with phytohormone(s) is one of the most promising, authentic and cost‐effective methods to mitigate the deleterious effect of salinity.The study was conducted to investigate potential of seed priming with gibberellic acid (GA3) to cope up with the adverse effects of salinity (0, 100, 200 and 300 mm NaCl) in pea (Pisum sativum L.) seedlings.There were different responses to salinity, which induced oxidative stress, higher accumulation of Na+ in shoots and roots and inhibition of photosynthetic traits. However, seed priming with GA3 showed promising effects on physiological traits under salinity stress and alleviated the adverse effects of salinity by inducing the antioxidant system, proline production, total phenol and flavonoid content and regulating ion homeostasis, along with up‐regulation of Na+/H+ antiporters (SOS1 and NHX1).Plants adapt and prevent high salt accumulation by inducing expression of Na+/H+ antiporter (SOS1 and NHX1) proteins that enhance Na+ sequestration. Thus, seed priming with GA3 is important in alleviation of high salinity stress and can be used as a criterion for developing salt‐tolerant cultivars. [ABSTRACT FROM AUTHOR]

Solanum americanum Mill. is a weed that occurs with a number of crops, and it is known for its high seed production and its staggered germination. The objective of this work was to evaluate the germination behavior of S. americanum seeds under the influence of chemical and environmental factors. In the laboratory, we tested the effect on germination of (i) constant and alternating temperatures, (ii) seed washing, (iii) exposure time and concentration of chemical treatments and (iv) seeding depth and soil covered with plant residue on seedling emergence. The variables analyzed were germination percentage, germination rate index, seedling emergence and length of the seedlings. The results indicated that alternating temperatures are the main way to promote germination of S. americanum; however, chemical treatments can help to increase the germination percentage and rate index. There was no increase in germination with seed washing, with the exception of KNO3 application. A GA3 concentration of 0.84 g L−1 and an exposure time of 21.22 h in 0.2% of KNO3 promoted the highest germination of S. americanum. Germination occurs when seeds remain on the soil surface and are not covered by crop residue. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of gibberellic acid (GA3), a terpenoid and phytohormone, on the digestive physiology and intermediary metabolism of the cotton bollworm Helicoverpa armigera Hübner (Lepidoptera, Noctuidae). Incorporation of GA3 (800 μg g−1 diet) in an artificial diet results in significant reductions in the rates of diet consumption and the efficiency of conversion of food consumption by by H. armigera larvae. The relative growth rate decreases as the concentration increases. The relative α‐amylase activity in sixth‐instar larvae of H. armigera decreases significantly after ingestion of four concentrations of GA3. Histological studies of the midgut in GA3‐treated larvae (800 μg g−1 diet) show degeneration of the epithelial cells. The alanine and aspartate aminotransferase activity decreases at the highest concentration. However, acid phosphatase, alkaline phosphatase, γ‐glutamyl transferase and lactate dehydrogenase activity increase significantly compared with the control. The results clearly demonstrate the adverse effects of GA3 on H. armigera via interruption of nutritional physiology and metabolism. [ABSTRACT FROM AUTHOR]

In degraded dryland systems, native plant community re‐establishment following disturbance is almost exclusively carried out using seeds, but these efforts commonly fail. Much of this failure can be attributed to the limited understanding of seed dormancy and germination traits.We undertook a systematic classification of seed dormancy of 26 species of annual and perennial forbs and shrubs that represent key, dominant genera used in restoration of the Great Basin ecosystem in the western United States. We examined germination across a wide thermal profile to depict species‐specific characteristics and assessed the potential of gibberellic acid (GA3) and karrikinolide (KAR1) to expand the thermal germination envelope of fresh seeds.Of the tested species, 81% produce seeds that are dormant at maturity. The largest proportion (62%) exhibited physiological (PD), followed by physical (PY, 8%), combinational (PY + PD, 8%) and morphophysiological (MPD, 4%) dormancy classes. The effects of chemical stimulants were temperature‐ and species‐mediated. In general, mean germination across the thermal profile was improved by GA3 and KAR1 for 11 and five species, respectively. We detected a strong germination response to temperature in freshly collected seeds of 20 species. Temperatures below 10 °C limited the germination of all except Agoseris heterophylla, suggesting that in their dormant state, the majority of these species are thermally restricted.Our findings demonstrate the utility of dormancy classification as a foundation for understanding the critical regenerative traits in these ecologically important species and highlight its importance in restoration planning. [ABSTRACT FROM AUTHOR]

Drought is one of the most serious environmental factors limiting production of sugarcane worldwide. In order to assess the influence of gibberellins (GA3) on drought and plant growth, along with associated physio‐biochemical attributes, expression of eight drought‐responsive genes were quantified and analysed.At grand growth stage (120 DAP) two sugarcane varieties (CoLk94184, CoPK05191) were exposed to drought by withholding irrigation. GA3 (35 ppm) was applied using battery‐operated uniform controlled dispensing sprayer twice at 1‐week intervals on 2‐week drought‐stressed plants. Physio‐biochemical attributes including antioxidant enzyme activities were estimated following standard protocols. RT‐PCR was performed to visualise the drought‐associated gene expression patterns.Drought triggered a reduction in RWC and chlorophyll content but these recovered when droughted plants were exposed to GA3. Proline content increased many fold in both varieties under stress, but decreased under the influence of GA3. There was a mixed response of antioxidant enzyme activity, which distinctly declined after GA3 exposure, together with a lesser reduction in dry matter content over that of control plants. With increasing stress, expression of pyrroline‐5‐carboxylase synthetase (P5CS) and betaine‐aldehyde dehydrogenase genes was observed, selectively up‐regulated in CoPK05191. Expression of proline oxidase/transporter was high in CoPK05191 but diminished along with proline content after exposure to GA3. CoLk94184 showed no significant difference in P5CS gene expression under stress condition, whereas expression of betaine‐aldehyde dehydrogenase gene was unchanged in response to stress.Results demonstrated that exposure of droughted plants to GA3 not only led to recovery of activity of drought‐associated physio‐biochemical attributes, but also minimised impact on cane dry weight and quality. Further, GA3 application caused differential gene expression that possibly triggers increased responsiveness towards drought tolerance in sugarcane. [ABSTRACT FROM AUTHOR]

We have isolated a severe dwarf mutant derived from a Ds ( Dissociation) insertion mutant rice ( Oryza sativa var. japonica c.v. Dongjin). This severe dwarf phenotype, has short and dark green leaves, reduced shoot growth early in the seedling stage, and later severe dwarfism with failure to initiate flowering. When treated with bioactive GA3, mutants are restored to the normal wild-type phenotype. Reverse transcription PCR analyses of 22 candidate genes related to the gibberellin ( GA) biosynthesis pathway revealed that among 22 candidate genes tested, a dwarf mutant transcript was not expressed only in one Os KS2 gene. Genetic analysis revealed that the severe dwarf phenotype was controlled by recessive mutation of a single nuclear gene. The putative Os KS2 gene was a chromosome 4-located ent-kaurene synthase ( KS), encoding the enzyme that catalyses an early step of the GA biosynthesis pathway. Sequence analysis revealed that osks2 carried a 1-bp deletion in the ORF region of Os KS2, which led to a loss-of-function mutation. The expression pattern of Os KS2 in wild-type cv Dongjin, showed that it is expressed in all organs, most prominently in the stem and floral organs. Morphological characteristics of the dwarf mutant showed dramatic modifications in internal structure and external morphology. We propose that dwarfism in this mutant is caused by a point mutation in Os KS2, which plays a significant role in growth and development of higher plants. Further investigation on Os KS2 and other Os KS-like proteins is underway and may yield better understanding of the putative role of Os KS in severe dwarf mutants. [ABSTRACT FROM AUTHOR]

GA3 and GA4 (gibberellins) play an important role in controlling gravitropism and tension wood formation in woody angiosperms. In order to improve our understanding of the role of GA3 and GA4 on xylem cell formation and the G-layer, we studied the effect of GA3 and GA4 and uniconazole-P, which is an inhibitor of GA biosynthesis, on tension wood formation by gravity in Fraxinus mandshurica Rupr. var. japonica Maxim. seedlings. Forty seedlings were divided into two groups; one group was placed upright and the other tilted. Each group was further divided into four sub-groups subjected to the following treatments: 3.43 × 10−9 μmol acetone as control, 5.78 × 10−8 μmol gibberellic acid (GA3), 6.21 × 10−8 μmol GA4, and 6.86 × 10−8 μmol uniconazole-P. During the experimental period, GAs-treated seedlings exhibited negative gravitropism, whereas application of uniconazole-P inhibited negative gravitropic stem bending. GA3 and GA4 promoted wood fibers that possessed a gelatinous layer on the upper side, whereas uniconazole-P inhibited wood formation but did not inhibit the differentiation of the gelatinous layer in wood fibers on the upper side. These results suggest that: (i) both the formation of gelatinous fibers and the quantity of xylem production are important for the negative gravitropism in horizontally-positioned seedlings; (ii) GA3 and GA4 affect wood production more than differentiation of the gelatinous layer in wood fibers; G-layer development may be regulated by other hormones via the indirect-role of GA3 and GA4 in horizontally-positioned F. mandshurica seedlings rather than the direct effect of GAs; and (iii) the mechanism for upward wood stem bending is different to the newly developed shoot bending in reaction to gravity in this species. [ABSTRACT FROM AUTHOR]

Amongst the plants (Arachis hypogaea) subjected to differential reproductive manipulations, the leaf levels of chlorophyll and sugar and the dry weight of the aerial plants increased more (except sugar level in defruited plant) in the deflorated plants than either in the defruited or control plants, and the order of senescence was: control > defruited > deflorated. Seed yield per plant increased in deflorated plants as a result of increase in the number of pods (sink size) and reduction in the sink strength (seed wt per pod). While 75% defoliation caused a decrease in all the parameters relating to senescence (chlorophyll, protein, reduced nitrogen, sugar and dry wt), 25% defoliation caused a slight decrease of chlorophyll level of leaf and aerial plant weight. However, the level of protein and reduced nitrogen in the leaf and sugar in the stem increased by the latter (through 25% defoliation). Defoliation up to 25% reduced seed yield by only 2%. Whereas the level of chlorophyll and aerial plant dry weight were not significantly changed by either kinetin or ABA, the level of protein and reduced nitrogen in the leaf and sugar level in both leaf and stem increased by kinetin. GA3 increased almost all the parameters studied. All the three phytohormones increased the yield, mainly by increasing the sink size rather than the sink strength. It is concluded that the aerial flowers are more lethal than the underground fruits in inducing whole plant senescence where the leaf senescence is uncoupled from fruit maturation in normal condition possibly due to sink limitation. [ABSTRACT FROM AUTHOR]

IAA and GA3 had increased the stem thickness by increasing that of cortex, phloem fibers and xylem. Each had increased straw and fiber yield/plant, but the effect was more pronounced with GA3 than IAA. The percentage of long fibers, strength and fineness increased significantly with GA3. The latter two properties decreased with IAA. [ABSTRACT FROM AUTHOR]

Germination of the polymorphic seeds and seedling growth of Atriplex triangularis under various salinity, gibberellic acid and kinetin treatments were determined. Gibberellic acid (GA3; 2.9 mM) promoted germination and growth at high NaCl concentrations (345 mM). Kinetin (4.7 μM) stimulated germination at all salinities and seed sizes tested. GA3 and kinetin generally increased seedling growth at all concentrations of salinity studied. Higher concentrations of kinetin were found to be inhibitory [ABSTRACT FROM AUTHOR]

Cambial activity and vessel differentiation of the Quercus robur stem were investigated in relation to concentration of growth regulators and sucrose, seasonal changes in the sensitivity of cambial cells, and axial polarity of the stem. Basipetal efflux of natural auxin was measured in the oak stem cambial region. IAA, GA3, kinetin and sucrose affected cambial activity and/or initiation of vessel differentiation differently, depending upon concentration. Depending upon the season, kinetin increased or reduced the stimulation of cambial activity caused by IAA and GA3, but it did not affect the differentiation of vessels. Supply of sucrose in higher concentrations reduced the number of differentiated vessels but did not decrease the stimulation of cambial divisions. Unlike stimulation of cambial activity by GA3, auxin stimulation of cambial divisions and differentiation of vessels were highly dependent upon stem polarity, 2,3,5-triiodobenzoic acid (TIBA) inhibited formation of vessels, but not cambial activity. The oscillations in basipetal efflux of natural auxin from the cambial stem region of successive 6 mm long sections substantiate the hypothesis that the histogenesis of xylem tissue in ring-porous species is under control of the vectorial field that is associated with oscillatory phenomena in polar auxin transport. [ABSTRACT FROM AUTHOR]

A wave-like pattern of the basipetal efflux of natural auxin from the cambial region: of a series of consecutive short sections of stems of Larix decidua Mill., Acer pseudaplatanus L. and Picea abies (L.) Karst. has been demonstrated as it was earlier reported for Pinus silvestris L. Apical application of ABA suppressed the IAA-stimulated increase of the auxin-wave amplitude, and zeatin or GA3 prevented this repression in stem segments of Pinus silvestris. All the exogenously applied substances were highly effective in physiological concentrations. Already 20-min of exposure to IAA or ABA at the apical end produced modulations of the auxin-wave along the whole 6.6cm long stem segment. Application of 2, 3, 5-triiodobenzoic acid (TIBA) caused suppression of the wave-like pattern of auxin efflux similarly as ABA, supporting the association of the modulatory effects of ABA with the phenomena involved in polar transport of auxin. Abscisic acid applied to the basal end of the stem segment also reduced the auxin-wave amplification caused by simultaneous supply of IAA to the apical end. This Ending additionally confirms the hypothesis that: 1) the supracellular auxin-wave generation is associated with the functioning of a system of oscillators coupled at the cellular level and 2) the auxin-wave modulations can be propagated acropetally, that is against the main direction of the auxin molecular transport. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum spp. hybrids) plants were exogenously supplied with, 0, 1.0, 1.5. and 2.0 mg gibberellic acid (GA3) per stalk in single and multiple applications. Increases in stalk fresh weight, total stalk length, and lengths of individual internodes were primarily a function of the interval between applications. Applications produced additive growth responses at 15- and 30-day intervals but not at 0- and 45-day intervals. [ABSTRACT FROM AUTHOR]

The effects of rolA on root and shoot architecture have been ascribed to a deficiency in gibberellic acid (GA3) and to changes in polyamine metabolism, Using tobacco, we examined interactions among (GA3, a polyamine accumulation inhibitor (α-DL-difluoromethylornithine or DFMO) and the rolA gene controlled by the 35S CaMV promoter We measured the effects of these three agents on architecture and polyamine accumulation in excised roots and whole plants grown in vitro. Previous work showed that DFMO or genetic transformation with the rolA gene from Agrobacterium rhizogenes, controlled by the 35S promoter (P35S-rolA), caused excised tobacco roots to grow faster with altered root system architeclure. We show that gibberellic acid (GA3) reversed the effects of DEMO on the architecture of excised root systems, but neither reversed the effects of DFMO on growth, nor the changes in growth and architecture associated with P35S-rolA. GA3 treatment alone resulted in increased agrnatine levels, suggesting that the inhibition of the effects of DFMO on architecture was through a stimulation of the arginine decarboxylase (ADC) pathway. GA3 alone also inhibited the accumulation of putrescine and tyramine conjugates in excised roots. In tobacco plants growing in vitro DFMO and P35S-rolA were associated with reduced shoot height, which was partially restored by GA3, treatment; however, GA3 also stimulated shoot height in the controls. GA3 did not lessen the leaf wrinkling associated with P P35S-rolA. P35S-rolA increased root number in young seedlings in vitro, and increased root system length in seedlings grown in soil. As in excised roots, the developmental changes linked to DFMO and P35s-rolA were accompanied by reductions in putrescine titers. GA3 treatment stimulated putrescine accumulation in stems and leaves, and partially reversed the negative effects of DFMO and P35s-rolA on putrescine accumulation in roots, stems and leaves. Again, the restoration of putreseine pools appeared to be through a stimulation of the ADC pathway, since agmatine accumulated in plants exposed to GA3. In general, the effects of DFMO and P35s-rolA on phenotype and polyamine metabolism were coordinated, and in many cases these effects were similarly modulated by GA3, reinforcing the previous conclusion that the phenotypic effects of rolA in roots and shoots occur through interference with polyamine metabolism and that the putrescine conjugates are particularly important in regulating root system growth and architccture. We were unable, however, to discem consistent evidence for a direct role for GA3 in establishing the RolA phenotype. [ABSTRACT FROM AUTHOR]

Gibberellins A1, A3, A4 and A7 were identified by combined gas chromatography-mass spectrometry (GC-MS) in leaf and stem tissues of 17-day-old seedlings of wheat (Triticum aestivum L.), cvs Siete Cerros (semi-dwarf, Rht1) and Møystad (tall), of F1 hybrids from the cross Møystad × Siete Cerros and of 2 selected lines from the cross Møystad × Sonora 64 (Rht1 and Rht2). GA1 and GA3 were identified by full scan mass spectra separately in all 5 extracts, GA4 and GA7 were identified by selected ion monitoring in a bulked fraction. About 90% of the biological activity (Tan-ginbozu dwarf rice bioassay) in all 5 extracts was due to the GA1/GA3-fraction. [ABSTRACT FROM AUTHOR]

To determine the response type, published data for the most widely used bioassays for gibberellins have been analyzed by means of a computer program for estimating sensitivity parameters, or by interpolation. The dose response data are almost uniformly subsensitive, i.e. more than an 81-fold increase in external gibberellin concentration is required for a change from 10 to 90% of maximal response (S90/S10). Data for the interaction of gibberellins with artificial membranes are, in contrast, markedly ultrasensitive (S90/S10 < 10). This difference further strengthens the view that lipid structures do not function as receptors for gibberellins. Most of the subsensitive dose responses for gibberellins can be quite precisely represented by cooperative isotherms. However, available data are insufficiently detailed for an unequivocal choice among cooperative, multiphasic or more complex kinetics. [ABSTRACT FROM AUTHOR]

Effect of gibberellic acid (GA3) on leaf sheath elongation in a normal (cv. Møystad) and a gibberellin (GA)-insensitive (c. Siete Cerros) genotype of wheat (Triticum aestivum L.) were studied at 18 and 12°C under short (SD, 12 h) or long (LD, 24 h) photoperiod. Leaf sheath length in cv. Møystad was signficantly increased by exogenous GA3 both under SD and LD. LD alone stimulated leaf sheath elongation and the combined effect of LD and GA3 was additive, and there was no statistically signficant interaction between photoperiod and GA3 under any conditions. However, there was a highly significant stimulation of leaf sheath elongation by LD in cv. Siete Cerros as well. These results indicate that stimulation of elongation growth in wheat leaves by LD is not mediated by gibberellin. [ABSTRACT FROM AUTHOR]