Stimulation of rice coleoptile growth by ethylene

Summary The growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C₂H₄ is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.This investigation was supported in part by research grants (FD-00071 and GM-12885) from the U. S. Public Health Service.     

Ethylene and carbon dioxide: regulation of oat mesocotyl growth

Either ethylene or carbon dioxide stimulated the growth of oat mesocotyls in darkness, although the effect was much greater for carbon dioxide. Maximum elongation was obtained in the presence of both gases. Ethylene also induced lateral expansion of the mesocotyl: the volume of the mesocotyl was increased more in air with added ethylene than in air depleted of ethylene. Ethylene also stimulated mesocotyl growth under red light. Gibberellin only slightly increased mesocotyl length under red light and acted cooperatively with ethylene in the promotion of growth. The oat mesocotyl is a unique organ in terrestrial plants because ethylene simultaneously stimulates not only longitudinal growth but also lateral expansion. The ecological significance of oat mesocotyl growth in relation to the response to ethylene and carbon dioxide is discussed.     

Interaction between ethylene,abscisic acid and gibberellic acid in elongation of rice mesocotyl

Summary Combined application of ethylene, abscisic acid and gibberellic acid produced marked partly synergistic stimulation of mesocotyl growth of japonica rice in darkness.     

Stimulation of ethylene production in detached rice leaves by vanadate

The effect of vanadate on ethylene biosynthesis in detached rice leaves was investigated. Vanadate at pH 5.0–7.0 effectively enhanced ethylene production within 3 h of its application. It promoted the conversion of ACC to ethylene. Treatment with vanadate did not decrease ACC level until late stage of incubation, i.e. at 12 h after incubation. Molybdate, an inhibitor of phosphatase had no or much less stimulatory effect on ethylene production than did vanadate at comparable concentrations. Azide, an inhibitor of F₁-ATPase, inhibited ethylene production in detached rice leaves. FC and vanadate were observed to be synergisticly increased ethylene production in detached rice leaves. In conclusion, plasma membrane H⁺-ATPase does not seem to be involved in ethylene biosynthesis in detached rice leaves.Abbreviations ACC 1-Aminocyclopropane-1-carboxylic acid - FC Fusicoccin     

The effects of syntheticdl-dormin (Abscisin II) on the growth of the oat mesocotyl

Summary The growth-inhibitory properties of syntheticdl-dormin (Abscisin II) and itstrans, trans isomer were assayed using the oat mesocotyl section. Growth of this tissue was promoted by IAA and GA; dormin inhibited the elongation caused by both compounds and also the small amount of growth that occurred in blank buffer. A given concentration of dormin inhibited growth to about the same proportion in all these cases. IAA and GA mixtures stimulated growth in the presence of 2.0 mg/l dormin slightly more than the sum of growth with IAA+2.0 mg/l and GA+2.0 mg/l dormin. At lower concentrations of dormin (0.02 mg/l and below) the relationship was reversed. Dormin inhibited growth slightly at 0.02 mg/l but below that concentration it had no observable effect.Kinetin did not affect mesocotyl elongation, nor did it interact with the inhibition of IAA- or GA-stimulated growth.Thetrans, trans isomer had 1/30th the activity of the natural 2-cis-4-trans compount; when they were assayed together in mixtures of different proportions the inhibitions were additive.Most experiments were carried out with GA₃ but dormin also inhibited the action of gibberellins 1, 4, 5, 6, 7 and 9. The action of dormin was not competitive with that of IAA or GA.The effect of dormin as an inhibitor of plant growth is discussed.     

Stimulation of mycelia growth in several mushroom species by rice husks

When supplemented to the culture medium of mushroom Coprinus cinereus, rice husks soaked beforehand in methanol stimulated mycelia growth up to a concentration of 80 mg/ml dose-dependently, whereas the non-treated stimulated mycelia growth up to 20 mg/ml. This result suggests the existence of both stimulatory and inhibitory substances in rice husks. Since momilactone A (MLA) is recognized as one of the phytoalexins in rice husks, its biological activity against mycelia growth was tested. Momilactone A inhibited mycelia growth at 5 microg/disc, whereas the methanol extract of husks did so at 1 mg/disc, wherein 0.2 microg of MLA was estimated by LC/MS/MS. Thus the phytoalexins including MLA should inhibit mycelia growth. Rice husks stimulated mycelia growth in some edible mushroom species such as Grifola frondosa (maitake), Lentinus edodes (shiitake), Pleurotus eryngii (eringi), and P. ostreatus (hiratake). Our findings might lead to the development of new profitable cultivation methods for mushrooms using rice husks.     

Growth, anatomy and morphology of the mesocotyl and the growth of appendages of the wild oat (Avena fatua L.) seedling

Morphological and histological studies were made on the mesocotyl and the emergence of seedlings of a nondormant strain (CS40) of wild oats (Avena fatua L.). The elongation of the mesocotyl was primarily responsible for the emergence of seedlings from deeper levels of soil. The mesocotyl of the seedling is here interpreted as the hypocotyl. The functionally suctorial scutellum together with coleoptile constitutes the first cotyledon and the first true-leaf is regarded as the second cotyledon. The development of tillers from scutellar and first-leaf buds depends on the depth at which level the seeds (caryopses) germinated and the seedlings emerged above the soil surface. The first-leaf axillary buds, regradless of depths, develop into dominant tillers. The scutellar buds, especially at greater depths, remain inhibited. At shallower levels, however, they develop into tillers. The scutellar buds, at deeper levels, behave as reserve ramets which feature adds to the success of the species as a weed in the agricultural prairies.     

Inhibition by light of growth and Golgi-localized glucan synthetase in the maize mesocotyl

When dark-grown maize (Zea mays L.) seedlings were exposed to red light (R), Golgi-localized glucan synthetase activity in the mesocotyl began to decrease within 1 h, and fell by approx. 70% in 12 h. The response required at least 10^-2 mol m^-2 R and saturated at 100 mol m^-2. Far-red light (FR) alone inhibited glucan synthetase, and FR reversed the inhibition by R back to the level caused by FR alone. Density gradient fractionation indicated that of the major membrane markers only the Golgi-localized glucan-synthetase activity was affected by R. Golgi-localized latent inosine-diphosphatase activity was unaffected. The kinetics of the response, the photon fluence dependence, and the reversibility by FR all correlated with the inhibition by light of elongation of the mesocotyl, indicating that light inhibits growth and glucan synthetase activity by a similar mechanism.Abbreviations FR far-red light - GS glucan synthetase - IAA indole-3-acetic acid - R red light     

On the mechanism of the “photo-geo” response in the mesocotyl of oat seedlings

Summary The photo-geo response comes about through the differential inhibition of cell growth on the two curved sides of the mesocotyl.     

Stimulation of lettuce seed germination by ethylene

Ethylene increased the germination of freshly imbibed lettuce (Lactuca sativa L. var. Grand Rapids) seeds. Seeds receiving either red or far-red light or darkness all showed a positive response to the gas. However, ethylene was apparently without effect on dormant seeds, those which failed to germinate after an initial red or far-red treatment. Carbon dioxide, which often acts as a competitive inhibitor of ethylene, failed to clearly reverse ethylene-enhanced seed germination. While light doubled ethylene production from the lettuce seeds, its effect was not mediated by the phytochrome system since both red and far-red light had a similar effect.     

Suppression and promotion of growth by ethylene in rice seedlings depends on ambient humidity

We examined the effect of ethylene on the growth of rice seedlings (Oryza sativa L.) at various degrees of humidity. Ethylene significantly suppressed the growth of shoots when applied to seedlings grown under 30% relative humidity (RH), but promoted the growth of shoots when applied to seedlings grown under 100% RH. The application of gibberellic acid (GA₃) promoted the elongation of shoots in seedlings grown under 30% and 100% RH. Ethylene inhibited the shoot elongation induced by GA₃ at 30% RH, but enhanced the elongation induced by GA₃ at 100% RH. These results indicate that ethylene can either promote or suppress the growth of rice shoots depending on ambient humidity, and that these actions of ethylene may be mediated through modulating the responsiveness of shoots to gibberellin.     

Stimulation of chlororespiration by heat and high light intensity in oat plants

High irradiance and moderate heat inhibit the activity of the photosynthetic apparatus of oat (Avena sativa L.) leaves. The incubation of oat leaves under high light intensity in conjunction with high temperatures strongly decreased the maximal quantum yield of photosystem (PS) II, indicating the close synergistic effect of both stress factors on PS II inhibition and the subsequent irreversible damage to the photosynthetic apparatus. The PS I A/B protein levels remained similar to control values in leaves incubated under high light intensity or moderate heat, and decreased only when both stress factors were simultaneously applied. Immunoblot analysis of thylakoid membranes using specific antibodies raised against the NDH-K subunit of the thylakoidal NADH dehydrogenase complex (NADH DH) and against plastid terminal oxidase (PTOX) revealed an increase in the amount of both proteins in response to high light intensity and/or heat treatments. In addition, these stress treatments were seen to stimulate the activity of electron donation by NADPH and ferredoxin to plastoquinone, the PTOX activity in plastoquinone oxidation and the NADH DH activity in thylakoid membranes. Incubation with n-propyl gallate (an inhibitor of PTOX) inhibited the increase of NDH-K and PTOX levels under high light intensity and heat, and slightly stimulated the activity of electron donation by NADPH and ferredoxin to plastoquinone. Antimycin A (an inhibitor of cyclic electron flow) increased the NADH DH activity and preserved the levels of NDH-K and PTOX in thylakoid membranes from leaves incubated under high light intensity and heat. The up-regulation of the PTOX and the thylakoidal NADH DH complex under these stress conditions supports a role for chlororespiration in the protection against high irradiance and moderate heat.     

Modulation of ethylene responses by OsRTH1 overexpression reveals the biological significance of ethylene in rice seedling growth and development

Overexpression of Arabidopsis Reversion-To-ethylene Sensitivity1 (RTE1) results in whole-plant ethylene insensitivity dependent on the ethylene receptor gene Ethylene Response1 (ETR1). However, overexpression of the tomato RTE1 homologue Green Ripe (GR) delays fruit ripening but does not confer whole-plant ethylene insensitivity. It was decided to investigate whether aspects of ethylene-induced growth and development of the monocotyledonous model plant rice could be modulated by rice RTE1 homologues (OsRTH genes). Results from a cross-species complementation test in Arabidopsis showed that OsRTH1 overexpression complemented the rte1-2 loss-of-function mutation and conferred whole-plant ethylene insensitivity in an ETR1-dependent manner. In contrast, OsRTH2 and OsRTH3 overexpression did not complement rte1-2 or confer ethylene insensitivity. In rice, OsRTH1 overexpression substantially prevented ethylene-induced alterations in growth and development, including leaf senescence, seedling leaf elongation and development, coleoptile elongation or curvature, and adventitious root development. Results of subcellular localizations of OsRTHs, each fused with the green fluorescent protein, in onion epidermal cells suggested that the three OsRTHs were predominantly localized to the Golgi. OsRTH1 may be an RTE1 orthologue of rice and modulate rice ethylene responses. The possible roles of auxins and gibberellins in the ethylene-induced alterations in growth were evaluated and the biological significance of ethylene in the early stage of rice seedling growth is discussed.     

Ethanol sensitivity of rice and oat coleoptiles

The ability to avoid the ethanol-induced injury was evaluated in rice ( Oryza sativa L.) and oat ( Avena sativa L.) coleoptiles. The growth of the rice and oat coleoptiles was inhibited by ethanol exogenously applied at concentrations greater than 200 and 30 m M , respectively. At 300 m M ethanol, oat coleoptiles were brown and flaccid but rice coleoptiles did not show any visible symptoms of toxicity. The acetaldehyde level in rice and oat coleoptiles was increased by exogenously applied ethanol and the increases were greater in oat than in rice coleoptiles under aerobic and anaerobic conditions. At 300 m M ethanol, the acetaldehyde concentrations in the rice and oat coleoptiles were 46 and 87 nmol g⁻¹ FW under aerobic conditions, respectively, and 52 and 124 nmol g⁻¹ FW under anaerobic conditions, respectively. The activity of alcohol dehydrogenase (ADH; EC 1.1.1.1) in the direction of ethanol to acetaldehyde was greater in oat than in rice coleoptiles and ADH protein in oat coleoptiles was more induced by exogenously applied ethanol than that in rice coleoptiles. These results suggest that in vivo conversion rate of ethanol to acetaldehyde by ADH is lower in rice than oat coleoptiles, which may be one of the reasons that ethanol sensitivity of rice is much lower than that of oat coleoptiles. The great ability of rice to avoid the ethanol-induced injuries may contribute its anoxia tolerance when glycolysis and ethanolic fermentation replace the Krebs cycle as the main source of energy under anaerobic conditions.     

Stimulation of ethylene or ethane production by malformin

Malformin stimulated ethylene production of Phaseolus vulgarisL. seedlings and explants. However, when malformin was vacuum-infiltratedinto apical bud sections, the production of ethylene was inhibited,ethane production was stimulated and the sections became softand pliable; in pure oxygen, ethylene production was- stimulatedand the sections remained firm. Prolonged stimulation of ethaneproduction by malformin-treated sections required oxygen. Indoleaceticacid (IAA) had no effect on the stimulation of ethane productionby malformin-infiltrated tissues; malformin and IAA stimulatedethylene production synergistically at the same time that malformininducedethane production had increased markedly. ¹This work was supported by grant GB-7158 from the NationalScience Foundation. ²Journal Paper No. 3560 of the Purdue Agricultural ExperimentStation. (Received July 23, 1969; )     

Effect of high temperature pre-treatment on elongation of the mesocotyl of rice seedlings I. Cell multiplication in the mesocotyl

Mesocotyl elongation in paddy rice seedlings of the japonicatype was markedly stimulated by high temperature pre-treatmentof seeds. Examination of the number of parenchyma cells perone cell layer in longitudinal sections of mesocotyl revealedthat stimulation may be mainly caused by cell multiplication. (Received February 24, 1970; )     

Studies on the growth of rice tissue under submerged condition II. The effect of light and 2,4-dichlorophenoxyacetic acid on elongation of coleoptile and mesocotyl rice seedlings

Plant Systematics and Evolution -     

Effects of applying stem-shortening plant growth regulators to leaves on root elongation by seedlings of wheat, oat and barley: mediation by ethylene

Several plant growth regulators (PGRs) commonly used in practicalfarming to restrict shoot height and control lodging were examined for theirimpact on root growth in naturally short or tall cultivars of barley (cvs.Kymppi and Saana), oat (cvs. Veli and Pal), and wheat (cvs. Mahti and Tjalve).The possible involvement of ethylene in the responses was also examined. Shootswere sprayed at the two-leaf stage with the gibberellin biosynthesis inhibitorsCycocel (chlormequat chloride) (CCC) or Moddus (Trinexapac-ethyl) (TE), or withthe ethylene-releasing agent Cerone (ethephon) (ETH) at 0, 0.1, 1, 10 or 50times the recommended agricultural rate (RR). Root elongation and ethyleneproduction by roots or shoots were unaffected by CCC at all application ratesorby TE at ×0.1 or ×1.0 RR. At ×10 and ×50 RR, TE wasinhibitory to root extension but did not increase ethylene biosynthesis bytheseroots or the shoots. ETH at ×0.1 or ×1.0 RR did not affect rootextension or ethylene production in roots or shoots. At all higher rates ofapplication ETH stimulated ethylene production strongly in shoots and roots ofall three species, while root elongation was retarded severely in barley,moderately in oat and only slightly in wheat. These differences in elongationresponse are attributed to differences in sensitivity to ethylene released byethephon. Accordingly, root elongation in wheat was only slightly affected whenethylene gas was supplied at concentrations up to 100 ppm for 3d. In contrast, root elongation in barley was strongly inhibitedbyethylene, with oat demonstrating an intermediate responsiveness.     

Stimulation of extracellular polysaccharide synthesis in oat protoplasts by the host-specific phytotoxin victorin

The host-specific phytotoxin victorin (HV-toxin) stimulates mesophyll protoplasts of susceptible but not of resistant oat (Avena sativa L.) to produce an amorphous, ethanol-insoluble extracellular material which stains with Calcofluor white and aniline blue. Over a 24-h period incorporation of [¹⁴C]glucose into ethanol-insoluble products is maximally stimulated by 60 pg victorin/ml, whereas at 6 ng/ml initial rates of incorporation are higher but the protoplasts collapse. The extracellular material produced in response to victorin is solubilized by cold 4.4 N NaOH and by commercial laminarinase and pectinase. Incorporation of [¹⁴C]glucose into cellulose (material resistant to Updegraff's acetic-nitric acid reagent) is stimulated as much as incorporation into other wall polysaccharides, but cellulose constitutes less than 15% of the total victorin-stimulated incorporation. Synthesis of ethanol-insoluble material that can be digested by pronase, i.e. protein, is inhibited by victorin above 60 pg victorin/ml. Formation of extracellular polysaccharide is stimulated at concentrations of victorin which cause almost complete inhibition of protein synthesis, indicating that de-novo protein synthesis is not involved. Preincubation of protoplasts with inhibitors of RNA or protein synthesis prevents both extracellular polysaccharide synthesis and cell death in response to victorin. Although previous studies have indicated a link between calcium and the action of victorin, several compounds which interact with calcium do not influence this response to victorin.Abbreviations EPS extracellular polysaccharide - SCM 0.5 M sorbitol +10 mM CaCl₂+5 mM 2-(N-morpholino)-ethanesulfonic acid (Mes), pH 5.8 This paper is dedicated to the memory of our teacher and colleague, Martin H. Zimmermann (1926–1984)     

The effect of ethylene on auxin-induced growth of excised rice coleoptile segments

Elongation growth induced by exogenous auxin of apical coleoptilesegments of etiolated rice seedlings was promoted by ethylene.In the absence of exogenous auxin, growth promotion was notobserved. The highest promotion by ethylene was obtained at10^–6 M of indole-3-acetic acid, a suboptimal concentrationfor auxin-induced elongation. Level of ethylene which achievedthe effect was less than 1 µl per liter of an incubationatmosphere. ¹Present address: The Ocean Research Institute, University ofTokyo, Nakano, Tokyo, Japan (Received May 27, 1970; )