Synergistic interaction of gibberellic acid and triazinone derivatives in the promotion of rice shoot growth

Forty-five 1,3,5-triazine-2,6-dione derivatives were synthesized and their plant growth-promoting activities examined by the rice (Oryza sativa) seedling test in the presence or absence of gibberellic acid (GA). For high activity in promoting the growth of rice seedlings and acting as active GA-synergists, a para-substituted or a 2,4-disubstituted phenyl group, a hydrogen atom and an alkoxy group were required in the 1-, 3- and 4-positions of the 1,3,5-triazine-2,6-dione molecule. 4-Ethoxy-1-(p-tolyl)-s-triazine-2,6(1H, 3H)-dione [TA], one of the most potent triazinones, synergized the effect of GA on the shoot elongation of different varieties of rice including normal type, dwarf mutants and chlorophyll-mutants. TA synergistically increased the growth-promoting activity of GA by both a simultaneous treatment at the same sites and separate treatments at separate sites of rice seedlings.     

Quantitative and qualitative changes in cell wall polysaccharides in relation to growth and cell wall loosening in Lactuca sativa hypocotyls

The correlation between hypocotyl elongation, cell wall loosening and changes in cell wall polysaccharides was studied using intact lettuce seedlings grown in the dark or in light together with gibberellic acid (GA) and/or 5-fluorodeoxyuridine (FUDR). The following results were obtained:
1) The production of pectic, hemicellulosic and cellulosic polysaccharides look place in parallel with hypocotyl elongation, which was substantially affected by different growth conditions.
2) The mole percentage sugar composition of pectic and hemicellulosic polysaccharides changed in response to dark, light, GA, or FUDR treatments.
3) The amounts of xylose and glucose in hemicellulosic polysaccharides and those of galactosc, rhumnose and uronic acid in pectic polysaccharides increased in parallel with hypocotyl elongation.
4) Statistical analysis of the quantitative relationship between sugars composing polysaccharides revealed that the uronic acid content changed in parallel with those of rhamnose and galactose in pectic polysaccharides, and the content of xylose varied in parallel with those of fucose and glucose.
5) The content of hemicellulosic polysaccharides was correlated with cell wall loosening represented by a decrease in the minimum stress-relaxation time. Changes in the stress-relaxation time value were correlated with those in the content of araltinose and galactose in hemicellulosic polysaccharides.
Based on these results, the relationship between hypocotyl elongation, changes in cell wall polysaccharides, and cell wall loosening is discussed with respect to the effect of GA and FUDR on hypocotyl elongation.     

Sterol composition of dwarf and tall Pisum sativum seedlings in relation to gibberellic-acid-enhanced shoot growth

Gibberellic acid (GA₃) stimulated shoot elongation in both dwarf and tall cultivars of pea, but more so in the dwarf cultivar. The sterol composition of shoots of both cultivars was similar, with sitosterol being the most abundant compound, followed by stigmasterol and campesterol. Cholesterol could not be detected. Following GA₃ application, levels of free sterols in whole shoots increased whereas glycoside levels tended to fall. The magnitudes of the changes in both classes of sterol were similar in both cultivars. Analyses of stems and leaves separately revealed a greater growth response to GA₃ in the former but no effect of the hormone on the sterol composition of either organ. It is concluded that GA₃ enhancement of shoot growth in pea is not mediated through quantitative changes in cell sterols.     

Root and shoot elongation of rhizotron-grown seedlings of Eucalyptus nitens and Eucalyptus globulus in relation to temperature

Information on the growth response of a crop plant in relation to temperature can be helpful in selecting genotypes to suit local environments, scheduling favourable time of planting and forecasting growth and yield. To determine the effects of varying temperature on root and shoot elongation of eucalypt seedlings, elongation rates of roots and shoots were measured in rhizotrons for two species (Eucalyptus nitens (Deane and Maiden) Maiden, and Eucalyptus globulus Labill.) at a temperature range of 5–23 °C. Within this range of temperatures, elongation rates of roots and shoots of both species increased with an increase in temperature. Roots of E. globulus were more sensitive and shoots less sensitive to temperature than those of E. nitens. However, the threshold temperature corresponding with zero elongation rate predicted from the regression of elongation rate against temperature was similar for the roots (∼5 °C) and shoots (∼0 °C) of both species. Hysteresis did not appear to have a significant influence on root or shoot elongation of both species during warming compared with cooling. Results are discussed highlighting the importance of the interaction between development and growth of plant components.     

赤霉素和脱落酸对黑稻黄化幼苗中胚轴伸长生长的作用研究

研究了不同浓度的GA和ABA对三种黑稻黄化幼苗中胚轴伸长生长的影响。结果表明 :1.2 5 μmol/L的GA和ABA对三种黑稻黄化幼苗中胚轴的伸长生长有显著的促进作用 ,GA效应高于ABA ;三个供试稻种中 ,黑帅对GA和ABA的反应最为显著 ,且GA和ABA对其有叠加效应     

Comparison of cell-walls of Lolium multiflorum with cotton cellulose in relation to their digestion with enzymes associated with cellulolysis

Activities of several enzymes associated with cellulolysis were compared using as substrates cell-walls of Lolium multiflorum and cotton cellulose. Purified enzymes C₁ (see Ref. 1 for definition), C._x (CM-cellulase) and β-glucosidase were employed as well as culture filtrates containing C_x. Activities were determined by ability to digest the substrates and to release H₂O-soluble phenolic compounds from the grass cell-walls. The culture filtrates most active on cotton cellulose were obtained using the fungi Trichoderma viride and Fusarium solani; with grass cell-walls the most active were from T. viride, Gliocladium roseum, a species of Basidiomycetes, and one strain of Myrothecium verrucaria (IMI Strain 25 291). For the crude enzyme preparations tested, there were highly significant correlations between the digestibility of grass cell-walls and the UV-absorption of the filtrate at λ_max 290 nm and at λ_max 324 nm but there was no significant correlation between the digestibility of grass cell-walls and that of cotton cellulose. Partially purified C₁ and C_x from two different fungal sources showed activity on both substrates. Differences in MW of the H₂O-soluble phenolic compounds obtained by treatment of grass cell-walls with C₁ and C_x components suggest that these enzymes could have different modes of action. Synergism between C₁ and C_x from T. koningii occurred with both substrates but with C₁ and C_x from F. solani synergism only occurred with cotton cellulose.     

Biosynthesis of phytohormones from novel rhizobacterial isolates and their in vitro plant growth-promoting efficacy

The health of the plant and soil fertility is dependent on the plant–microbes interaction in the rhizosphere. Microbial life tends to endure various rhizosphere plant–microbe interactions. Phytohormones such as auxins, cytokinins, gibberellic acid, ethylene and abscisic acid are termed as the classical group of hormones. Out of the 70 rhizobacterial strains isolated from the Coleus rhizosphere, three different rhizobacterial strains Pseudomonas stutzeri MTP40, Stenotrophomonas maltophilia MTP42 and Pseudomonas putida MTP50 having plant growth-promoting attributes were isolated and characterized for its phytohormone-producing ability. The phytohormones such as indole 3-acetic acid (IAA), gibberellic acid and cytokinin (kinetin and 6-benzyladenosine) were affirmed in culture supernatant of the above isolates. IAA was detected in all the three isolates, where in highest production was found in S. maltophilia MTP42 (240?µg/mL) followed by P. stutzeri MTP40 (250?µg/mL) and P. putida MTP50 (233?µg/mL). Gibberellic acid production was found maximum in MTP40 (34?µg/mL), followed by MTP42 (31?µg/mL) and MTP50 (27?µg/mL). The cytokinin production from the isolates, namely, MTP40, MTP42 and MTP50 were 13, 11 and 7.5?µg/mL, respectively. The isolates showing the production of plant growth enhancing phytohormones can be commercialized as potent bioformulations.     

Enzyme activities in Pennisetum seedlings germinated in the presence of abscisic and gibberellic acids

Effects of abscisic acid (ABA) and gibberellic acid (GA₃), alone and in combination, on growth and activity of alanine aminotransferase (GPT), aspartate aminotransferase (GOT), and glutamate dehydrogenase (GLDH) were studied in aerial parts of Pennisetum typhoides seedlings. ABA inhibited growth and activity of GLDH, but stimulated the activity of GPT and weakly that of GOT. GA₃, on the other hand, did not affect the activity of any of the enzymes tested, but in combination with ABA tended to antagonise the efrect of the latter.     

Peroxidase isoenzymes of the Avena coleoptile

The bulk of the peroxidases of Avena coleoptile sections exist in soluble and salt-extractable, wall-associated fractions with lesser amounts in membranous and wall-bound fractions. In the presence of auxin the peroxidase levels remain nearly constant while in the absence of auxin the peroxidase of each fraction increases 2-to 6-fold in 22 hr. There are qualitative and quantitative changes in the isoenzyme patterns with time, but these changes are independent of auxin. It is concluded that the peroxidase changes are induced by isolation of the tissues from the coleoptile and are unrelated to the growth rate.     

Agmatine deiminase in rice seedlings

Agmatine deiminase activity in rice embryos increased gradually upto 24 hr during germination and then decreased. Gibberellic acid and kinetin inhibited the activity when added to the germination medium. The enzyme was purified 717 fold with specific activity 788.5 nkat/mg protein and yield 8.8%. The M_r of the native enzyme was 18.3 x 10⁴ and the enzyme was a dimer of two identical subunits. The pH and temperature optimum of the enzyme were 6.0 and 28° respectively. The enzyme followed typical Michaelis-Menten kinetics with a K_m value of 1.5 x 10^?2 M. The enzyme activity was inhibited by various divalent cations and spermidine and spermine, but putrescine showed no effect.     

Isolation,purification and characterization of adenosine triphosphatase from mitochondria of rice seedlings

A new and improved procedure is described for the isolation and purification of adenosine triphosphatase (F₁ ATPase) from rice seedling mitochondria. The enzyme has a multi-subunit structure, as revealed by electron microscopy and SDS-mercaptoethanol gel electrophoresis. Oligomycin sensitivity as well as cold lability of this enzyme clearly prove that the mitochondria of monocotyledons have an ATPase similar to the F₁ ATPases from other sources.     

Free sterols and glycolipids in the aleurone tissue of germinating wheat

The action of gibberellic acid on wheat aleurone tissue led to reduced levels of free sterols and glycolipids compared with control tissue. Radio-labelled precursors were not incorporated into sterols or glycolipids, although mevalonate and glycerol were incorporated into polyisoprenoid hydrocarbon and phospholipid respectively. It is concluded that sterols and glycolipids are not synthesized in the tissue during germination; this is in contrast to earlier reports of the active, gibberellin-regulated metabolism of phospholipids.     

Catechol O-methyltransferases in pampas grass: differentiation of m- and p-methylating activities

Partially purified catechol O-methyltransferase from pampas grass (Cortaderia selloana) catalyses the methylations of substrates at both their meta and para positions. This capability was shown, by heat treatments, to arise from a less stable m-O-methyl-transferring activity and a more stable p-O-methyltransferring activity, tested against protocatechuic acid. When acting upon caffeic acid, the preparation catalyses a reaction of solely m-O-methyltransfer (in contrast to the mixed methylation of this substrate exhibited by rat liver catechol O-methyltransferase). A small degree of m-O-methylation of monophenolic substrates also occurs.     

Interconversion of gibberellin A1 to gibberellin A8 in seedlings of dwarf Oryza sativa

[³H]Gibberellin A₁ ([³H]GA₁)applied to seedlings of dwarf rice (Oryza sativa L. cv. Tanginbozu) was metabolized to GA₈. Identification of GA₈, was made by gas-liquid radiochromatography using three liquid stationary phases.     

Metabolism of added gibberellic acid in Malus pumilla in relation to cool storage breakdown

Gibberellic acid (GA₃) that was injected into the core of apples to reduce internal breakdown, was found to accumulate in the cortical tissue during cool storage only to a limited extent and never exceeded 0.5 % of the added dose. Limitations on the commercial use of GA₃ would appear to be associated with the low level of incorporation into susceptible tissue.     

Plant growth-promoting traits of Streptomyces with biocontrol potential isolated from herbal vermicompost

Three strains of Streptomyces (CAI-21, CAI-26 and MMA-32) were earlier reported by us as having potential for biocontrol of charcoal rot of sorghum, caused by Macrophomina phaseolina (Tassi) Goid., and plant growth promotion (PGP) of the plant. In the present investigation, the three Streptomyces were characterised for their physiological traits (tolerance of salinity, temperature, pH and resistance to antibiotics) and further evaluated in the field for their PGP of rice, grown by a system of rice intensification methods. All three Streptomyces were able to grow in NaCl concentrations of up to 12% (except MMA-32), at pH values between 5 and 13 and temperatures between 20 and 40°C. They were highly resistant to ampicillin and trimethoprim (>800 ppm), sensitive to chloramphenicol, kanamycin and nalidixic acid (50–100 ppm) and highly sensitive to streptomycin and tetracycline (5–25 ppm). When evaluated for their PGP activity on seedlings of rice, % germination and shoot and root lengths were significantly enhanced over the control. In the field, the Streptomyces strains significantly enhanced the panicle length, filled grain numbers and weight, panicle weight, 1000 seed weight, tiller numbers, total dry matter, root length (39–65%), root volume (13–30%), root dry weight (16–24%), grain yield (9–11%) and stover yield (11–22%) over the control. In the rhizosphere soil (0–15 cm from root) at harvest, the population of actinomycetes was significantly enhanced as was microbial biomass carbon (27–83%) and nitrogen (24–43%), dehydrogenase activity (34–152%), available P (13–34%) and N (30–53%) and % organic carbon (26–28%). This study further confirms that the selected Streptomyces have PGP properties.     

Restoration of gibberellin biosynthesis by 2,6-diisopropylphenoxyacetic acid in uniconazole-treated rice plants

2,6-Diisopropylphenoxyacetic acid (DIPA), a promoter of growth and flowering of Sagittaria species, was found to improve the shoot growth of rice plants treated with uniconazole, an inhibitor of gibberellin (GA) biosynthesis. In a modified micro-drop bioassay using semi-dwarf rice, Oryza sativa L. cv. Tan-ginbozu, in which uniconazole had been incorporated into the agar medium, a significant recovery from growth inhibition was observed for both the 3rd and the 4th leaf sheaths but not for the 2nd sheath. In greenhouse experiments, uniconazole-treated rice plants partially recovered from growth inhibition when DIPA was applied after uniconazole treatment, whereas DIPA applied with, or before, uniconazole treatment did not improve growth. The levels of GA₁ and GA₂₀ in the rice plants treated with uniconazole plus DIPA were almost equal to those of the untreated controls, indicating that the observed growth recovery is attributable to the restoration of GA biosynthesis by DIPA.     

Indole-3-acetyl-myo-inositol in kernels of Oryza sativa

IAA-myo-inositol was isolated from kernels of Oryza sativa and characterized by its chromatographic properties and its mass spectral fragmentation pattern. This is the first demonstration of the occurrence of a myo-inositol ester of IAA in a plant other than Zea mays.