The effect of some growth regulators on light-induced germination of Paulownia tomentosa seeds

Grubišié, D., Konjevié, R. and Neškovié, M. 1988. The effect of some growth regulators on light-induced germination of Paulownia tomentosa seeds. - Physiol. Plant. 72: 525–528.
The germination of Paulownia tomentosa Steud. (Empress tree) seeds can be induced either by red light (R) or by exogenously applied gibberellic acid (GA₃). The R induced germination is completely suppressed by far red irradiation, abscisic acid (ABA) or by growth retardants such as ancymidol, tetcyclacis and paclobutrazol, though not by AMO 1618 or chloro-choline chloride (CCC). The inhibition caused by far red light (FR) and growth retardants can be overcome by GA₃, while the ABA-induced inhibition can be reversed by fusicoccin (FC), which does not reverse the inhibition caused by FR or growth retardants. It is noteworthy that the germination of light insensitive wheat, corn, alfalfa and mung bean seeds is not inhibited by growth retardants.     

The embryonic axis controls lipid catabolism in cotyledons of apple seeds during germination

Activities of alkaline lipase (AlkL, EC 3.1.1.3), isocitrate lyase (ICL, EC 4.1.3.1), glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and pyruvate kinase (PK, EC 2.7.1.40) were determined in embryos of apple ( Malus domestica Borb. cv. Antonówka) during culture in darkness or at 12 h photoperiod; in both cases either in the presence of gibberellin A₃ (GA₃) or AMO 1618 (inhibitor of GA synthesis). AlkL and ICL were stimulated by light and GA₃; light stimulation was reversed by AMO. G6PDH and PK were not affected by culture conditions. Almost all the activity of all enzymes was found in the cotyledons; only PK was distributed between axis and cotyledons. GA-like activity was found almost exclusively in the embryo axis. Cultured isolated cotyledons lost their sensitivity to light and AMO, but AlkL and ICL were still stimulated by GA₃. Translocation of GA from axis to cotyledons during the culture of embryos is postulated.     

Growth-promoting activity of gibberellins on shoot elongation in Salix pentandra is reduced by 16,17-dihydro derivatisation

The metabolism of GA₁₀ is thought to be under photoperiodic control in the woody plant Salix pentandra . However, in a recent study using 16,17-[³H₂]GA₁₉ as a mimic of Ga₁₀, no effect of photoperiod was found on its metabolism to 16,17-dihydro-GA₂₀ and 16,17-dihydro-GA₁. To investigate if this was due to differential action of exogenous 16,17-dihydro-GAs and GAs, the effects of the 16,17-dihydro-derivatives of the gibberellins GA₁₉, GA₁, and GA₁ as compared with their parent GAs, on shoot elongation in seedlings of S. pentandra were studied. 16,17-Dihydro-GA₁₉, and -GA₂₀ were both almost inactive, while 16,17-dihydro-GA₁ induced some shoot elongation in seedlings treated with ancymidol as well as under short days. GA₁₉, GA₂₀ and GA₁ were all able to counteract the inhibitory effect of ancymidol under continuous light, while inhibition induced by a 12-h photoperiod was antagonised only by GA₂₀ and GA₁. Thus, the growth-stimulating activity of the tested GAs is significantly reduced by 16,17-dihydro derivatisation, but the derivatives do not inhibit stem elongation in S, pentandra , as has been found in monocotyledons.     

Interaction of potassium ions and gibberellin in the control of hypocotyl growth in Amaranthus caudatus

Potassium promotes growth in several plant tissues. Elongation growth of the hypocotyls of Amaranthus caudatus L. ev. Lalsag is mainly controlled by gibberellins, but K⁺ also promotes growth. In the present study the interaction of K⁺ with gibberellin (GA₃) and chlorocholine chloride (CCC) has been investigated. When K⁺ was applied externally in the dark, hypocotyl growth was promoted in the seedlings. External application of GA₃ did not promote growth in the dark. GA₃ was effective in the light and K⁺ was synergistic with GA₃ in promoting elongation. Application of CCC in the dark makes the seedlings sensitive to GA₃. The inhibition of growth by CCC was also reversed by K⁺. The results indicate a possible role of K⁺ in GA₃ induced elongation of hypocotyls.     

Internode length in Pisum. Comparison of genotypes in the light and dark

There is a strong relationship across the full range of gibberellin deficient, internode length genotypes ( le, lh, is, na ) between internode length in the dark and in red or white light. Further, the new, more severe allele at the le locus. Ie ^d, is shown to influence growth in the dark as well as in the light. These results suggest that darkeness does not specifically overcome any of the steps blocked by the gibberellin (GA) synthesis genes contrasting with the conclusions drawn by other workers. Supporting this conclusion in relation to the Ie gene are results which show that, at least at certain dosage rates, dark-grown Ie na plants respond better to GA₁ than to GA₂₀ similar to the response previously reported in light grown plants.
The greater response by plants of the nana line NGB1766 ( na ) to GA₁ in the dark than in the light suggests that light may influence internode length by altering GA-sensitivity. These results are discussed in relation to previous views on the control of stem elongation by light.     

Relation between relative growth rate, endogenous gibberellins, and the response to applied gibberellic acid for Plantago major

Relationships between relative growth rate (RGR), endogenous gibberellin (GA) concentration and the response to application of gibberellic acid (GA₃) were studied for two inbred lines of Plantago major L., which differed in RGR. A4, the fast-growing inbred line, had a higher free GA concentration than the slow-growing W9, as analyzed by enzyme immunoassay. GA₃ application increased total plant weight and RGR₃ particularly for the slow-growing line. Chlorophyll a content and photosynthetic activity per unit leaf area were decreased, while transpiration rate was unaffected by GA₃ application. The increase in RGR by GA₃ application was associated with an increased leaf weight ratio; specific leaf area and percentage of dry matter in the leaves were only temporarily affected. Root respiration rate per unit dry weight was unaffected.
The correlation between low RGR, low GA concentration and high responsiveness to applied GA₃ supports the contention that gibberellins are involved in the regulation of RGR. However, the transient influence of GA₃ application on some growth components suggests the involvement of other regulatory factors in addition to GA.     

Effects of prohexadione (BX-112) and gibberellins on shoot growth in seedlings of Salix pentandra

Effects of gibberellins A₁, A_4/7, A₉, A₁₉ and A₂₀ and growth retardants were studied on shoot elongation in seedlings of Salix pentandra L. The growth-retarding effects of CCC and ancymidol were antagonized by all the gibberellins tested. The novel plant growth regulator prohexadione (free acid of BX-112), which is suggested to block 3β-hydroxylation of gibberellins, effectively prevented shoot elongation in seedlings grown under long photoperiod. Initiation of new leaves was only slightly reduced. GA₁, but not GA₁₉ and GA₂₀, was active in overcoming the inhibition of stem elongation of seedlings, treated with prohexadione, GA₁₉, GA₂₀ and GA₁ are native in S. pentandra , and the results are compatible with the hypothesis that GA₁ is active per se in shoot elongation, and that the effect of GA₁₉ and GA₂₀ is dependent on their conversion to GA₁.
A mixture of GA₄ and GA₇ was as active as GA₁ in promoting shoot elongation in seedlings treated with prohexadione, while GA₉ showed slight activity only when applied at high doses.     

Internode length in Lathyrus odoratus. The involvement of gibberellins

Evidence was obtained by gas chromatography-mass spectrometry and gas chromatography-selected ion monitoring for the presence of gibberellin A₂₀), GA₁, GA₂₉, GA₈ and 2-epiGA₂₉ in vegetative shoots of tall sweet pea, Lathyrus odoratus L. Both tall (genotype L –) and dwarf (genotype II ) sweet peas elongated markedly in response to exogenous GA₁ attaining similar internode lengths at the highest dose levels. Likewise internode length in both genotypes was reduced by application of the GA biosynthesis inhibitor, PP333. The ratio of leaflet length to width was reduced by application of PP333 to tall plants and this effect was reversed by GA₁. When applied to plants previously treated with PP333, GA₂₀ promoted internode elongation of L – plants as effectively as GA₁, but GA₂₉ was not as effective as GA₁ when applied to II plants. In contrast, GA₂₀ and GA₁ were equally effective when applied to the semidwarf lb mutant but GA-treated lblb plants did not attain the same internode length as comparable GA-treated Lb – plants. The difference in stature between the tall and dwarf types persisted in dark-grown plants. It is concluded that GA₁ may be important for internode elongation and leaf growth in sweet pea. Mutant l may influence GA₁ synthesis by reducing 3β-hydroxylation of GA₂₀ whereas mutant lb appears to affect GA sensitivity.     

Internode length in Pisum. IV. The effect of the Le gene on gibberellin metabolism

The highly active, polar gibberellin-like substance found in the apical region of shoots of tall (genotype Le ) peas ( Pisum sativum L.) is shown by combined gas chromatography-mass spectrometry (GC/MS) to be GA₁. This substance is either absent or present at only low levels in dwarf ( le ) plants. Multiple ion monitoring (MIM) tentatively suggests that GA₈ may also be present in shoot tissue of tall peas. Gibberellin A₁ is the first 3 β-hydroxylated gibberellin positively identified in peas, and its presence in shoot tissue demonstrates the organ specificity of gibberellin production since GA₁ has not been detected in developing seeds. Application of GA₁ can mask the Le/le gene difference. However, whilst Le plants respond equally to GA₂₀ and GA₁, le plants respond only weakly to GA₂₀, the major biologically active gibberellin found in dwarf peas. These results suggest that the Le gene controls the production of a 3 β-hydroxylase capable of converting GA₂₀ to GA₁. Further support for this view comes from feeds of [³H] GA₂₀ to Le and le plants. Plants with Le metabolise [³H] GA₂₀ to three major products whilst le plants produce only one major product after the same time. The metabolite common to Le and le plants co-chromatographs with GA₂₉. The additional two metabolites in Le peas co-chromatograph with GA₁ and GA₈.     

Internode length in Pisum. III The effect and interaction of the Na/na and Le/le gene differences on endogenous gibberellin-like substances

In the garden pea ( Pisum sativum L.), shoots of the extremely short plants with the mutant na (phenotype nana) are found by bioassay to contain undetectable levels of gibberellin-like substances. This is confirmed by the use of near isogenic lines differing at the Na locus. Thus, mutant na appears to block a step early in the pathway of gibberellin synthesis. It is suggested that the polar gibberellin-like substance found in the apical portion of shoots of tall ( Le ) but not dwarf ( le ) peas could be GA₁. Extracts of shoots of na Le peas treated with GA₂₀ (the major active gibberellin in dwarf peas) possess a large amount of GA₁-like activity whereas extracts of shoots of na le peas treated with GA₂₀ possess a much reduced amount. Thus, gene Le may allow the conversion of a less active gibberellin (GA₂₀) into one more active in stimulating elongation in the pea (the GA₁-like compound). In contrast to their influence in the shoot, the na and Le genes do not appear to be operative in controlling the gibberellin content of developing seed, indicating that organ specific gibberellin biosynthesis and metabolism occur in peas.     

Detection and identification of gibberellins in Douglas fir (Pseudotsuga menziesii) shoots

Extracts of Douglas fir ( Pseudotsuga menziesii [Mirb.] Franco) shoots were purified by reversed and normal phase HPLC; gibberellin (GA)-like compounds detected by radioimmunoassay with antibodies against GA₄ and the Tan-ginbozu dwarf rice micro-drop biossay were analyzed by GC-MS. Three major components were identified as GA₄, GA₇, and GA₉ while smaller amounts of GA¹, GA₃ and putative GA⁹-glucosyl ester were also present.     

Interaction of gibberellic acid and photoperiod on leaf sheath elongation in normal and gibberellin-insensitive genotype of wheat

Effect of gibberellic acid (GA₃) on leaf sheath elongation in a normal (cv. Møystad) and a gibberellin(GA)-insensitive (cv. 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 concentrations. Leaf sheath length in cv. Siete Cerros was not significantly affected by 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.     

Role of endogenous gibberellins in germination of melon (Cucumis melo) seeds

The effect of the plant growth retardants ancymidol. mefluidide and uniconazole on germination of two melon accessions differing in their ability to germinate at 14°C was examined. The accessions were the cold sensitive Noy Yizre'el and the cold tolerant Persia 202. The three growth retardants were able to delay the germination of intact Noy Yizre'el seeds, but did not affect that of intact Persia 202 seeds. On the other hand germination of decoated seeds of both accessions was unaffected by these inhibitors at normal oxygen concentration, but was inhibited at 5% oxygen. When gibberellin-like activity was measured by a dwarf rice biological assay following HPLC fractionation, it was found that seeds of Persia 202 contained much more gibberellin-like activity than Noy Yizre'el seeds. Among the extracted compounds several endogenous gibberellins were identified by combined gas chromatography-mass spectrometry (GC-MS). They included GA₄, GA₂₀, GA₁ and GA₃ in Noy Yizre'el and GA₃₄, GA₂₀, GA₁ and GA₈ in Persia 202. It is suggested that the better germination of intact Persia 202 seeds, compared to Noy Yizre'el seeds at low temperature and low oxygen concentration, is due to a higher endogenous level of GA and a better seed coat permeability to oxygen.     

Ethylene-dependent action of gibberellin in seed germination of Amaranthus caudatus

The role of gibberellins in the germination of seeds of Amaranthus caudatus L. was examined. Tetcyclacis (BAS 106), an inhibitor of gibberellin biosynthesis, inhibited germination of the seeds. The inhibition caused by BAS 106 was antagonised by gibberellin A₄₊₇ (GA₄₊₇). Ethephon (2-chloroethylphosphonic acid) and 1-aminocyclopropane-1-carboxylic acid (ACC) could replace GA₄₊₇. Ethephon and ACC counteracted also the side effects of BAS 106 that are not reversible by GA₄₊₇. The rate of seed germination was not increased by gibberellin in the presence of aminoethoxyvinylglycine (AVG). AVG increased the effect of BAS 106. GA₄₊₇ could not reverse the effect of BAS 106 when AVG was simultaneously applied. The results indicate that the biosynthesis of endogenous gibberellins may be required for germination of A. caudatus seeds and that main physiological effects of GA₄₊₇ on seed germination may depend on ethylene biosynthesis.     

Growth and gibberellin relations of the extreme dwarf dx tomato mutant

The extreme dwarf d ^x tomato ( Lycopersicon esculentum Mill.) mutant has very short internodes which were found to contain shorter and fewer epidermal cells. The leaves are highly abnormal. The mutant showed a substantial stem growth response to GA₃, without approaching normal stature or morphology. The active gibberellin GA₁ and its precursors GA₁₉ and GA₂₀ were identified by coupled gas chromatography-mass spectrometry (GC/MS) in d ^x shoots. Quantitative GC/MS revealed that GA₂₀ accumulated to far higher levels than normal in stems and leaves of the mutant.     

Interactions between hydrogen cyanide, gibberellin, abscisic acid and red light in germination of lettuce seeds

Germination of lettuce ( Lactuce sativa L. cy. Grand Rapids) seeds was promoted by red light and by pulse treatments with gibbercllie acid (GA₃) or hydrogen cyanide, whereas it was inhibited by short exposure of seeds to absusic acid (ABA). The eflects of unsalLirating red light and of 10 μ M GA₃ on lettuce germination were completely reversed the effect of ABA (100 μ M ). In contrast, hydrogen cyanide did not reverse the effect of 100 μ M ABA and only partly eliminated the effect of 10μ M ABA, independently of the sequence of treatments. Possible interactions between HCN GA₃, ABA and red light were discussed. It was concluded thai light GA₃ and HCN affect different mechanisms involved in lettuce germination: ABA counteracts the stimulatory action of all these faclors. being the most effective against cvanide Additional key words - Lactuca sativa, pholodormancy, phylohormoncs.     

Metabolism of C19- and C20-gibberellins by cell-free preparations from immature Phaseolus coccineus seed

Gibberellin biosynthesis pathways were investigated using isotopically-labelled C₁₉- and C₂₀-gibberellins and cell-free preparations from immature seed of Phaseous coccineus cv. Prizewinner. The initial steps in an early 13-hydroxylation pathway involved the conversion gibberellin A₁₂-aldehyde (GA₁₂-aldehyde) to GA₁₂ which was 13-hydroxylated to yield GA₅₃, Metabolism of GA₅₃ yielded GA₄₄. In contrast to other cell-free systems, GA₄₄ was not further converted, either as a δ-lactone or an open-lactone structure, to the C-20 aldehyde GA₁₉. GA₁₉ was, however, metabolised to GA₂₀, GA₅ and GA₁. GA₂₀ represented a branch point in the pathway as it was converted both to GA₁, which was an end product, and GA₅ which was further converted to GA₆. Like GA₁, GA₆ was also an end-product of the early 13-hydroxylation pathway.
A non-13-hydroxylation pathway involving GA₄, GA₁₅, GA₂₄ GA₃₇ and GA₃₆ also originated from GA₁₂. The terminal product of this pathway was the 3β-hydroxy C₁₉-gibberellin, GA₄.