Root Growth Of Rice Seedlings Research Articles

Relative importance of Na+, Cl−, and abscisic acid in NaCl induced inhibition of root growth of rice seedlings

The relative importance of endogenous abscisic acid (ABA), as well as Na+ and Cl− in NaCl-induced responses related to growth in roots of rice seedlings were investigated. The increase in ammonium, proline and H2O2 levels, and cell wall peroxidase (POD) activity has been shown to be related to NaCl-inhibited root growth of rice seedlings. Increasing concentrations of NaCl from 50 to 150 mM progressively decreased root growth and increased both Na+ and Cl−. Treatment with NaCl in the presence of 4,4′-diisothiocyano-2,2′-disulfonic acid (DIDS, a nonpermeating amino-reactive disulfonic acid known to inhibit the uptake of Cl−) had less Cl− level in roots than that in the absence of DIDS, but did not affect the levels of Na+, and responses related to growth in roots. Treatment with 50 mM Na-gluconate (the anion of which is not permeable to membrane) had similar Na+ level in roots as that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate effected growth reduction and growth-related responses in roots in the same way as 100 mM NaCl. All these results suggest that Cl− is not required for NaCl-induced responses in root of rice seedlings. Endogenous ABA level showed no increase in roots of rice seedlings exposed to 150 mM NaCl. It is unlikely that ABA is associated with NaCl-inhibited root growth of rice seedlings.

Cell wall peroxidase activity, hydrogen peroxide level and NaCl-inhibited root growth of rice seedlings

The changes in cell-wall peroxidase (POD) activity and H2O2 level in roots of NaCl-stressed rice seedlings and their correlation with root growth were investigated. Increasing concentrations of NaCl from 50 to 150 mM progressively reduced root growth and increased ionically bound cell-wall POD activity. NaCl had no effect on covalently bound cell-wall POD activities. The reduction of root growth by NaCl is closely correlated with the increase in H2O2 level. Exogenous H2O2 was found to inhibit root growth of rice seedlings. Since ammonium and proline accumulation are associated with root growth inhibition caused by NaCl, we determined the effects of NH4Cl or proline on root growth, cell-wall POD activity and H2O2level in roots. External application of NH4Cl or proline markedly inhibited root growth, increased cell-wall POD activity and increased H2O2 level in roots of rice seedlings in the absence of NaCl. An increase in cell-wall POD activity and H2O2 level preceded inhibition of root growth caused by NaCl, NH4Cl or proline. NaCl or proline treatment also increased NADH-POD and diamine oxidase (DAO) activities in roots of rice seedlings, suggesting that NADH-POD and DAO contribute to the H2O2 generation in the cell wall of NaCl- or proline-treated roots. NH4Cl treatment increased NADH-POD activity but had no effect on DAO activity, suggesting that NADH-POD but not DAO is responsible for H2O2 generation in cell wall of NH4Cl-treated roots.

Cell wall peroxidase against ferulic acid, lignin, and NaCl-reduced root growth of rice seedlings

Summary The changes in cell wall peroxidase activity against ferulic acid (FPOD) and lignin level in roots of NaCl-stressed rice seedlings and their correlation with root growth were investigated. Increasing concentrations of NaCl from 50 to 150 mmol L −1 progressively decreases root growth. The reduction of root growth by NaCl is closely correlated with the increase in FPOD activity extracted from the cell wall. In contrast, lignin level was reduced by NaCl. Since proline and ammonium accumulations are associated with root growth inhibition caused by NaCl, we determined the effect of proline or NH 4 Cl on root growth and FPOD in roots. Exogenous application of NH 4 Cl or proline markedly inhibited root growth and increased FPOD activity in rice seedlings in the absence of NaCl. An increase in FPOD activity in roots preceded inhibition of root growth caused either by NaCl, NH 4 Cl, or proline. Our results suggest that cell-wall stiffening catalyzed by FPOD may participate in the regulation of root growth reduction of rice seedlings caused by NaCl.

Allelochemicals of the tropical weed Sphenoclea zeylanica

Nine plant growth inhibitors were isolated from the tropical weed Sphenoclea zeylanica, which shows allelopathic properties. Those compounds hitherto not reported from any plant source were the isomers of cyclic thiosulfinate, (1 S,3 R,4 R)-(+)- and (1 R,3 R,4 R)-(−)-4-hydroxy-3-hydroxymethyl-1,2-dithiolane-1-oxides, and (2 R,3 R,4 R)-(−)- and (2 S,3 R,4 R)-(+)-4-hydroxy-3-hydroxymethyl-1,2-dithiolane-2-oxides. These were named zeylanoxide A, epi-zeylanoxide A, zeylanoxide B and epi-zeylanoxide B, respectively. The absolute configurations at C-3 and C-4 were elucidated by chemical synthesis of both enantiomers from l- and d-glucose. Two of the inhibitors were secologanic acid and secologanoside, and three other inhibitors were by known secoiridoid glucosides formed as artifacts during extraction with methanol. The cyclic thiosulfinates and secoiridoid glucosides completely inhibit the root growth of rice seedlings at 3.0 mM. While the specific activity of the inhibitors was not high, since they accumulated to circa 0.61% S. zeylanica by dry weight, this suggests that the inhibitors are nervertheless potent allelochemicals in this weed.

Allelopathic activity and movement of water leachate from Mexican sunflower (Tithonia diversifolia (Hemsl.) A. Gray) leaves in soil.

Laboratory experiments were conducted to determine the phytotoxic activity of water leachates from Mexican sunflower [Tithonia diversifolia (Hemsl.) A. Gray] leaves and the effect of water movement on efficacy of the leachate in soil. The water leachates from both the green and senescent leaves applied onto soil inhibited root growth of rice seedlings. The phytotoxicity of leaf leachate depended on the concentration of phytotoxic substances which was determined by the amount of leaves extracted. Mobility of phytotoxic substances from Mexican sunflower leaves in soil was dependent on water movement and soil moisture conditions. More downward movement was observed in dry soil than in wet soil. The inhibitory activity of water leachate in soil was well correlated with the concentration in soil-water. The allelopathic potential of Mexican sunflower leaves in natural field was discussed.

Proline accumulation is associated with inhibition of rice seedling root growth caused by NaCl

The effects of NaCl on changes in the proline level in roots and root growth of rice seedlings were investigated. NaCl was effective in inhibiting root growth and in increasing proline accumulation in roots. Mannitol was also effective in inhibiting root growth, but proline accumulation was observed only at the concentration iso-osmotic with 150 mM NaCl. Accumulation of proline in roots preceded inhibition of root growth caused by NaCl. The inhibition of root growth and accumulation of proline in roots by NaCl are reversible. Exogenous l-proline and gabaculine, which were found to enhance in an accumulation of proline in roots, inhibited root growth of rice seedlings. The relationship between growth inhibition of roots caused by NaCl and changes in the proline level in roots is discussed.

Disturbed ammonium assimilation is associated with growth inhibition of roots in rice seedlings caused by NaCl

The effects of NaCl on changes in ammonium level and enzyme activities of ammonium assimilation in roots growth of rice (Oryza sativa L.) seedlings were investigated. NaCl was effective in inhibiting root growth and stimulated the accumulation of ammonium in roots. Accumulation of ammonium in roots preceded inhibition of root growth caused by NaCl. Both effects caused by NaCl are reversible. Exogenous ammonium chloride and methionine sulfoximine (MSO), which caused ammonium accumulation in roots, inhibited root growth of rice seedlings. NaCl decreased glutamine synthetase and glutamate synthase activities in roots, but increased glutamate dehydrogenase activity. The growth inhibition of roots by NaCl or MSO could be reversed by the addition of L-glutamic acid or L-glutamine. The current results suggest that disturbance of ammonium assimilation in roots may be involved in regulating root growth reduction caused by NaCl.

Cd induced changes in proline level and peroxidase activity in roots of rice seedlings

The effects of Cd on changes in proline level and peroxidase activity in roots of rice seedlings were investigated. CdCl2 was effective in inhibiting root growth and in accumulating proline in roots. The inhibition of root growth by Cd is reversible. The reduction of root growth induced by Cd is closely associated with accumulation of proline in roots. External application of proline markedly inhibited root growth of rice seedlings in the absence of Cd. Ionically bound, but not soluble, peroxidase activity in roots was increased by CdCl2. Proline treatment also resulted in an increase in ionically bound peroxidase activity in roots. The relationship between growth inhibition of roots induced by Cd and changes of proline level and peroxidase activity is discussed.

Interaction between optical isomerism and plant pharmacological action, change of modes of action and chirality of 1‐(α‐methylbenzyl)‐3‐p‐tolylurea

AbstractThe optical isomers, (R)‐1(α‐methylbenzyl)‐3‐p‐tolylurea ((R)‐MBU) and (S)‐1‐(α‐methylbenzyl)‐3‐p‐tolylurea ((S)MBU), which are analogues of daimuron [1‐(α,α‐dimethylbenzyl)‐3‐p‐tolylurea], a herbicide for Cyperaceae weeds and a safener for paddy rice, exhibited different biological responses. These two physiological properties of daimuron were observed separately in (R)‐MBU and (S)‐MBU. Only (R)‐MBU had herbicidal activity against Cyperaceae weeds, while the (S)‐isomer was a more effective safener against bensulfuron‐methyl (BSM) injury of rice seedlings than was (R)‐MBU. (S)‐MBU promoted root growth of rice seedlings, but the (R)‐enantiomer inhibited root growth. (S)‐MBU was a more potent inhibitor than (R)‐MBU on PS II reaction of spinach broken chloroplasts. Furthermore, (S)‐MBU and (R)‐MBU showed cross intergenus selective phytotoxicity among the Gramineae plants, Oryza sativa L. (rice, cv. Tsukinohikari, japonica), Triticum aestivum L. (wheat, cv. Norin No. 61) and Echinochloa crusgalli var. frumentacea Wight, on root growth inhibition in the dark.

Structure-Activity Relationships of (±)-Cucurbic Acid Analogs on the Root Growth of Rice Seedlings and Height of Young Corn Plants

ククルビン酸のすべての立体異性体および種々の類縁体をラセミ体にて立体選択的に合成し, 構造活性相関の解明ならびに農業上実用可能な植物生長調節剤の探索を目的として, これら化合物について水稲の幼苗根およびトウモロコシの草丈の成長に対する阻害活性を調べた. その結果, 水稲の幼苗根の成長阻害活性を高めるククルビン酸類縁体の化学構造要因として, 1) 1位と2位の置換様式がシスであること, さらに, 2) 3位の水酸基, 3) (Z)-2′-petenyl あるいはbutyl基に代表される2位の alkenyl あるいは alkyl 置換基, および, 4) 1位の methyl acetate 置換基が重要であることが解明された. 水稲の幼苗根の成長阻害活性において, ククルビン酸類縁体の中で, 相当する3-oxo体である, ジャスモン酸メチルあるいはエピジャスモン酸メチルに勝るものはなかったが, 茎葉処理によるトウモロコシ草丈の成長阻害活性においては, これらの化合物と同等あるいは若干強い活性を示す化合物がいくつか見い出された. これにより, より実用的な茎葉処理においては, 3位がケトンであるより水酸基のほうが, また, 2位の置換基が alkenyl よりも alkyl 基のほうが活性発現に適していると推測された.

Isolation and characterization of a factor from Bipolaris zeicola race 3 that induces susceptibility in rice plants.

Bipolaris zeicola race 3, which was originally reported as a pathogen causing a leaf spot disease of corn, was found to cause a leaf spot disease on rice plants when inoculated in greenhouse. A factor inducing susceptibility to a non-pathogenic isolate of Alternaria alternata only in rice plant leaves was isolated from the culture filtrates of race 3 by ethyl acetate extraction, TLC, and HPLC. The factor was characterized as a compound with the unique molecular formula of C30H44O8 from 1H-NMR, 13C-NMR and mass spectra analyses and was named as SIF 1. SIF 1 at concentrations higher than 10μg/ml induced the susceptibility, but neither inhibited root growth of rice seedlings nor caused necrosis or chlorosis on rice leaves even at 250μg/ml. However, SIF 1 may not be the primary determinant of B. zeicola race 3 responsible for the pathogenicity in rice plants, because SIF 1 was not detected in spore-germination fluids of race 3, even though the fluids strongly induced a susceptibility on rice leaves, and also because B. zeicola race 1, B. victoriae and B. bicolor, which are non-pathogenic to rice plants and known to be closely related to B. zeicola race 3, also produced SIF 1 during culture in nutrient medium. SIF 1 may be used as a suppressor probe for the analysis of resistance of rice plants.

A new indolic antiauxin, α-(5,7-dichloroindole-3-)isobutyric acid: its chemical synthesis and biological activity

A new potent antiauxin, α-(5,7-dichloroindole-3-)isobutyric acid has been synthesized and shown to inhibit auxin-mediated elongation ofAvena coleoptiles and to stimulate root growth of rice seedlings. Its activity is stronger than α-(p-chlorophenoxy)isobutyric acid and is comparable to that of 2,3,5-triiodobenzoic acid, which are typical antiauxins.

3-Hydroxyuridine, an allelopathic factor of an African tree, Baillonella toxisperma

A plant growth inhibitor was isolated from Baillonella toxisperma, a plant which may cause an allelopathic effect in the tropical rain forest of Cameroon. From spectral and chemical evidence, the inhibitor was identified as 3-hydroxyuridine. It inhibited both hypocotyl and root growth of cucumber and radish seedlings, and also inhibited root growth of rice seedlings, but not sheath growth. The foliar treatment of 3-hydroxyuridine exhibited inhibitory effects on the growth of a wide variety of weeds; however, it was quite ineffective against the growth of the crop plant, Zea mays. The strong plant growth inhibitory activity, together with the occurrence in most parts of the tree at high levels, indicated that 3-hydroxyuridine may be involved in the allelopathy of the tree.

Effect of organic amendments on seedling infection of rice caused byRhizoctonia solani

Soils amended with organic amendments such as rice chaff, mustard cake, neem cake, saw dust and farm yard manure significantly reduced the seedling infection of rice owing toRhizoctonia solani. Significant increase in shoot growth was noticed in soils amended with organic amendments while reduction in root growth of rice seedlings was also observed owing to the addition of organic amendments such as sunflower cake, mustard cake, coconut cake and farmyard manure.

Isolation of Vibsanines A, B, C, D, E and F fromViburnum odoratissimum.

A bioassay survey was conducted of constituents of leaves of Viburnum odoratissimum Ker., a “fish poison” plant. The bioassays led to the isolation of a new piscicidal compound vibsanine A (TLm against Oryzias latipes, 0.18 μg/ml), a new plant growth inhibitor vibsanine B (IC50 against root growth of rice seedlings, 57 μg/ml) and related compounds vibsanines C, D, E and F.

Effect of soil microorganisms on the growth of roots in rice seedlings

Abstract Nitrite formation by rhizoplane microorganisms of rice seedlings was examined in comparison with that by nonrhizosphere paddy soil microorganisms. Effect of nitrite on root growth of rice seedlings was also investigated under aseptic water culture condition. Rhizoplane microorganisms accumulated much nitrite than the other microorganisms in a root extract medium. The accumulated nitrite maintained a stationary level for more than 2 days. In glucose enriched media, both group of microorganisms accumulated nitrite only temporarily. Formation of lateral roots and root hairs was stimulated in the solution containing 1.12-11.2 ppm NO2 --N but elongation of primary roots was depressed under 5.6-11.2 ppm NO2 --N concentrations. Growth of rice seedlings was inhibited at concentrations higher than 5.6 ppm. Comparative studies indicated that effect of soil microorganisms on root morphology would have been caused by nitrite produced by rhizoplane microorganisms.

Bioactive compounds in leaves of Viburnum odoratissimum Ker. I. Isolation of vibsanines A,B,C,D,E and F from Viburnum odoratissimum.

A bioassay survey was conducted of constituents of leaves of Viburnum odoratissimum Ker., a “fish poison” plant. The bioassays led to the isolation of a new piscicidal compound vibsanine A (TLm against Oryzias latipes, 0.18 μg/ml), a new plant growth inhibitor vibsanine B (IC50 against root growth of rice seedlings, 57 μg/ml) and related compounds vibsanines C, D, E and F.

Increase of auxin-antagonistic action in 3-phosphoryloxycarbostyrils

Introduction of phosphoryloxy group at C-3 in carbostyrils has been found to increase auxin-antagonistic action. 3-Phosphoryloxycarbostyrils were synthesised from 3-hydroxycarbostyril and 3-hydroxy-4-phenylcarbostyril (viridicatin). The phosphates at very low concentrations markedly stimulated the root growth of rice seedlings, and competitively inhibited the IAA-induced lamina inclination in rice explants.

EFFECT OF THE CELLULAR CONSTITUENTS OF THE NITROGEN-FIXING BLUE-GREEN ALGA, CYLINDROSPERMUM MUSCICOLA, ON THE ROOT GROWTH OF RICE PLANTS

The present observation indicates that, besides the nitrogenous compounds, other biologically active cell constituents like vitamin B12 and auxins may also appreciably contribute to the fertilizing action of the nitrogen-fixing blue-green algae. Of the various intracellular amino acids of Cylindrospermum muscicola, cystine, tyrosine and phenylalanine seem to be available to the rice plants. The alga can synthesize vitamin B12 active compounds, the yield of which was about 1.2 to 1.5μg/g dry weight of the alga. The synthesis of these compounds was promoted by the addition of cobalt salt. The alga also contains interconvertible auxin-like substances which stimulate the root growth of rice seedlings.