Wheat Coleoptiles Research Articles

Plant responses to homœopathic remedies

SummaryOver the past 50 years several experiments to demonstrate the biological effects of homœopathic potencies have been devised. All of them have had short-comings: mainly in terms of reproducibility of the method itself and the analysis of the results. This paper describes a simple biological model using the growth responses of wheat coleoptiles to various homœopathic potencies. The results described show that the method is reproducible and that biological activity can be detected at extremely high dilutions. Succussion appears to be an essential part of the preparation of a homœopathic potency. A theoretical basis for this observation is discussed.

Synthesis of 15-carboxy-(?)-kaurenes

From the readily available (−)-kaurene and 6β-acetoxy-18-methoxycarbonyl-(−)-kaurene the corresponding 15-carboxy derivatives have been synthesized. In biotests on the elongation of wheat coleoptiles and the introduction of the synthesis of α-amylase in isolated wheat endosperms, these compounds do not exhibit gibberellin-like activity.

Auxin Activity of 3-Hydroxymethyl Oxindole in Wheat

Summary A plotcoxidation product of indole-3-acetic acid (IAA), 3-hydroxymethyl oxindole (HMO), is as effective as IAA in stimulating elongation of wheat coleoptile sections, even at a lower concentration. IAA fails to show stimulation of growth after pretreatment of the coleoptiles with chemicals inhibiting oxidation of IAA, but the growth promoting effect of HMO remains unaffected by such pretreatments. In time-course experiments also, the stimulatory effect of HMO is same as IAA. HMO prepared from IAA from different sources are effective to the same extent in stimulation of elongation of wheat coleoptiles.

Polyamines, storage substances and abscisic acid‐like inhibitors during dormancy and very early activation of Helianthus tuberosus tuber tissues

Abstract Dormancy and break of dormancy of tubers of Helianthus tuberosus L. (Jerusalem artichoke) have been investigated in regard to the possibility that polyamines can control these processes. Polyamines were detected by the method of direct dansylation and abscisic acid was bioassayed using wheat coleoptile growth test. Arginine and glutamine, which are the main store nitrogenous organic compounds of Helianthus tuberosus tuber, decrease during the last phase of dormancy as well as abscisic acid; moreover the corresponding increase in polyamines (putrescine, spermidine and spermine) seems to be strictly related to the break of dormancy of tuber. The artificial break of dormancy induced by 2,4‐dichlorophenoxyacetic acid stimulates a great increase in polyamines, just evident within 15 min after activation, and a corresponding decrease in arginine and glutamine. The levels of polyamines, at 1 h of activation are sufficient to stimulate protein synthesis in vitro.

Auxin-like Growth Activity of 3-Phenylpropionitrile from Water-Cress (Nasturtium officinale R. Br.)

Solutions of 3-phenylpropionitrile (PPN) and 3-phenylpropionic acid (PPA) exhibited auxin-like plant growth activity by stimulating elongation of sections cut from wheat coleoptiles and garden-cress hypocotyls. Elongation of sugar-beet hypocotyl sections was stimulated by PPA but not by PPN. Although PPA stimulated elongation of pea-epicotyl sections after 19 h incubation, most concentrations of PPN did not show activity until 70 h. PPN generally stimulated adventitious root formation on hypocotyls of garden-cress and sugar-beet, and on epicotyls of pea seedlings whereas dilute solutions of PPA were inactive and concentrated solutions were toxic. Steam distillates of water-cress plants contained a substance with auxin-like growth activity and chromatographic properties similar to PPN.

Levels of Extractable Abscisic Acid in the Mesocarp and Seed of Persisting and Abscising Peach Fruit1

Abstract Developing fruits of peach (Prunus persica (L.) Batsch cv. Andross) were classified as to abscission potential on the basis of fruit growth rate during stage I. Levels of inhibitors, as determined by wheat coleoptile and cress seed assays, were parallel in mesocarp and seed. Extracts from fruits with a high abscission potential contained significantly lower levels of an abscisic acid-like inhibitor than did those with low or intermediate potential. Thus ABA content appears to be positively correlated with the rate of fruit growth, and increases in concentration as the fruit is approaching maturity.

A Simple Bioassay for Abscisic Acid and Other Antitranspirants

Several diverse bioassays are available for experimental studies of abscisic acid (ABA). They include acceleration of abscission in petiole explants (Addicott et al ., 1949); inhibition of a-amylase synthesis (Goldschmidt and Monelise, 1968); inhibition of growth in wheat coleoptiles (Wright, 1969), wheat embryos (Milborrow, 1967), Lemna (Tillberg, 1975) and Spirodela (van Staden and Bornman, 1970); decrease in the amount of reducing substances formed in barley endosperm (Sivori, Sonvico and Fernandez, 1971); and stomatal closure in Commelina epidermal strips (Tucker and Mansfield, 1971; Ogunkami et al., 1973). While the last of these bioassays refers to stomatal closure, possible injury during preparation of isolated epidermal strips, rhythmic variation in stomatal aperture and the need for accurate measurement of pore size can present some difficulties. A possible solution to these problems associated with stomatal closure was revealed during an examination of the effect of a growth regulator from Eucalyptus (G) in the mung bean rooting bioassay (Dhawan, Paton and Willing, 1979). In this bioassay, G markedly reduced water uptake. An examination of this ABA-like effect of G suggested that water uptake by excised mung bean hypocotyls can provide a direct, quantitative bioassay for the 'antitranspirant activity' of ABA. Seeds of mung bean ( Vigna radiata L.) Wilczek, previously Phaseolus aureus Roxb. cv. Berken) were purchased locally. These were soaked for 3 h in tap water and then sown 2 cm deep in pots containing perlite (Australian Gypsum, Sydney). Seedlings were raised under glass house conditions with day temperature between 27 and 32 °C and night temperature between 18 and 25 °C. A plastic cover was used during the first three days to maintain high humidity. Darkness was imposed during the next 3 days to enhance hypocotyl elongation, but normal light was used during the last 4 days. Under these conditions, 10-day-old seedlings had developed fully expanded primary leaves at the first node. Seedlings selected for uniformity in height (^ 15 cm) and leaf size, and were excised 5 cm below the cotyledons. The excision was done under water to avoid entry of air. Subsequent operations were carried out in a growth cabinet at 25 °C and 12 h fluorescent light (17-5 W m-2) having a gentle air current. The seedling cuttings were cultured in 3 ml narrow mouth glass vials (4-0 cm long, 0*8 cm diam.) filled with water and were protected from wilting under a plastic cover for 1 day. At the end of this adjustment period, cuttings were selected for uniformity of water uptake before transfer to a new set of glass vials which were completely filled with test solutions. Care was taken to ensure that the upper meniscus of the solution was at the top edge of the vials. The uptake of water from each vial was recorded after 24 h by refilling the vial back to the top edge using a finely graduated hypodermic syringe. As the f. wt of cuttings was not markedly affected by treatment and the surface evapora-

Pattern of growth regulating substances in the leaves of vernalized sugar-beet during flowering period

The changes in the levels of growth regulating substances using the wheat coleoptile straight growth test were determined in the leaves of vernalized (flowering) and non-vernalized (non-flowering) plants of sugar-beet, cv. Poly-AG-Poland at two stages; the end of vernalization treatment (210 days from planting) and full-flowering stage. IAA was detected only in the extracts of the leaves of non-vernalized plants after210 days from planting. No inhibitory activity was detected, except in the case of the concentrated extract of the leaves of non-vernalized plants. This growth promoting zone was found at Rf 0.5–0.8 in the leaves of flowering plants after cold treatment and at flowering time. This zone of growth promoting action was suggested to have a major role in the flowering of sugar-beet.

Isolation and identification of two new biologically active norditerpene dilactones from Aspergillus wentii

Abstract Two new biologically-active norditerpenoid dilactones were purified from culture extracts of Aspergillus wentii and assigned the trivial names wentilactone A and wentilactone B. The absolute chemical structure of wentilactone A was determined by single crystal X-ray diffraction and circular dichroism. The structure of wentilactone B was determined by 1 H and 13 C NMR analyses. Wentilactone A had an ld 50 of 7.0 mg/kg when administered orally to 1-day-old chickens. Both metabolites inhibited growth in wheat coleoptile bioassays.

Depolarization of transmembrane potential of corn and wheat coleoptiles under reduced water potential and after IAA application

The influence of IAA and temporarily reduced water potential on the transmembrane potential (PD) of corn and wheat coleoptile sections was investigated. The studies were performed by two different methods: discontinuous PD measurements with microelectrodes in corn coleoptile sections and continuous measurements with microelectrodes in wheat coleoptile sections. Both methods showed a very rapid depolarization of PD within a period of 2 to 5 min. In corn coleoptile sections, a PD oscillation was observed within an average period of 14.5 min after IAA application and of 14.0 min after reduction of water potential. The PD amplitude was about 20 to 25 mV. In wheat coleoptile sections, an oscillation of PD could not be definitely established. After an IAA-induced depolarization period of 4 to 7 min, the initial potential sometimes was restored, while in some other cases, a subsequent hyperpolarization was found although in most cases the depolarization continued. The discussion covers the possibility that a decrease in PD caused by IAA and water stress may induce activation of H+ secretion by a plasmalemma H+ pump.

Effects of humic acid fractions on invertase activities in plant tissues

The effect of some soil organic matter fractions and synthetic humic acids were tested on the invertase activities in tissues of several higher-plant species. The effects varied according to the plant and soil organic matter fraction used. Thus no fraction tested had any effect on the invertase activity of beetroot storage tissue, but several fractions, mainly humic acid and its residues obtained by water or acid boiling, inhibited invertase in carrot storage tissues and wheat roots and coleoptiles. and to a lesser extent mungbean hypocotyls. Soil phenolic acids were without effect in any of the plant tissues tested. Some stimulations of invertase activity occurred with pea root tissue, using the water- and acid-soluble humic-acid fractions. The effects were independent of ash contents, total N or the C:H:N ratio, and could not be ascribed to any particular chemical component. The inhibitory effects on wheat invertase activity produced by soil organic matter were independent of pH in the range 4.5–7.0, and were constant over a 4 h incubation. The inhibitors only slightly affected the K m but markedly affected the V max of the reaction, hence they were non-competitive. The effect of a naturally-occurring invertase inhibitor from beetroot storage tissues could be reduced in the presence of humic acid. Although the inhibitor had little effect on wheat root invertase it did reduce the inhibitory effect of the humic acid in this tissue.

The effect of cytochalasin B on the rate of growth and ultrastructure of wheat coleoptiles and maize roots

Cytochalasin B (CB) inhibits the elongation growth of maize roots, and that of wheat coleoptile segments incubated in indolyl-3-acetic acid, by over 30% after a lag period of about 60 min. This long lag is not due to poor tissue penetration by the inhibitor, but seems to reflect a property of the process inhibited by CB. The only visible ultrastructural change accompanying growth inhibition is the accumulation of secretory vesicles in the vicinity of dictyosomes, which occurs between 90 and 300 min. However, a massive accumulation of vesicles is seen after 120 min in root cap cells which possess very active dictyosomes. The results indicate that CB does not inhibit elongation growth by interfering with cytoplasmic streaming. Instead, they indicate that the drug acts to inhibit the secretion of cell wall components at some stage after vesicle production, but prior to their transport.

The effect of kinetin and auxin on the chloroplast structure and chlorophyll content in wheat coleoptiles

Kinetin and auxin when applied to excised segments of wheat coleoptiles bring about changes in chloroplast structure and chlorophyll content of parenchymatous cells. Auxin (IAA) alone at a concentration of 10-5M stimulated the elongation (growth), but the chloroplast membrane system was less developed and the chlorophyll content was lowest in comparison with control and other variants. Kinetin (KIN) exhibited various effects depending on the concentration used. 10-6M KIN somehow stimulated the elongation and enhanced the amount of grana coming to one chloroplast section, but the individual grana were relatively small and the chlorophyll content a little higher than in the control. On the other hand 10-5M KIN which did not promote the elongation of wheat coleoptiles, had the maximum stimulatory effect on the chloroplast membrane system, especially on the occurrence of large grana, and the chlorophyll content was highest in comparison with the other variants. The occurrence of starch grains in chloroplasts was lower than in the other variants. The effect of a joint treatment of KIN and IAA did not exceed that of KIN (10-5M) alone. Thus the development of chloroplasts and the accumulation of chlorophyll in wheat coleoptiles are stimulated by the concentration of KIN which does not promote the elongation of coleoptiles.

Studies on plant growth‐regulating substances LV. The Plant growth‐promoting properties of some β‐aryl‐propionic acids

SUMMARYA series of 17 β‐arylpropionic acids were synthesised and examined for plant growth‐regulating activity in wheat and pea tests. The results are discussed in relation to chemical structure. The activity of β‐(2, 4‐dichlorophenyl)propionic acid was compared with those of the 2, 4‐dichloro‐derivatives of phenoxyacetic, phenyithioacetic and phenylimino acetic acids using the same tests. When wheat coleoptiles or pea stem tissues were incubated with solutions of β‐(2, 4‐dichlorophenyl)propionic acid no chromatographic evidence of β‐oxidation of the side chain or other type of degradation was obtained.

Components of Axillary Bud Inhibition in Rose Plants. IV. Inhibitory Activity of Plant Extracts

Extracts of rose stems have an inhibitory effect on rose bud breaking and on the elongation of wheat coleoptiles. The inhibitory activity of stem extracts is proportional to the amount of extracted tissue and is partially antagonized by auxin. Boiling the extract destroys this activity only partially. The level of ABA is higher in the basal part of the stem than in the upper part. After pruning there was a reduction in ABA level in the stem part close to both sprouting and nonsprouting buds. The ABA accumulated in subtending leaves of nonsprouting buds.

Wheat Chloroplast Development Under Lindane Treatment

Under laboratory conditions lindane (hexachlorocyclohexane) in an equivalent concentration of 4 kg/ha delayed the ageing of the chloroplasts in wheat coleoptiles. The first leaf which is smaller, thicker, and yellowish as compared to the control, has an ultrastructurally alterated chloroplast, evident by the reduced number of thylakoids, the presence of big starch grains and of some osmiophilic drops.

Uptake and Growth-promoting Activity of Indoleacetic Acid in Segments of Cold-hardened Wheat Coleoptiles

Seedings of winter wheat (Triticum aestivum L. cv. Kharkov MC 22) were grown at 24 C (unhardened) and 4 C (hardened). Indoleacetic acid (IAA) was added to excised coleoptile segments after lengthy incubation and their responses were determined by photometric auxanometry at both 25 C and 5 C. The segments' rates of uptake of (14)CIAA were also compared at both temperatures. Cold hardening had no significant effect on the rates of elongation and uptake in a saturating concentration of IAA (2 to 10 muM) at either temperature. Elongation was more sensitive to temperature of measurement than was uptake. At suboptimal concentrations of IAA and 25 C, hardened coleoptiles took up [2-(14)C]-IAA twice as fast but elongated half as fast as unhardened coleoptiles. This and the lack of effect of cold hardening on apparent uptake of [1-(14)C]-IAA raised the possibility that a higher rate of IAA-decarboxylation was coupled with the higher rate of uptake of IAA by hardened coleoptiles. Homeostatic hormonal regulation was also evident in the same endogenous rates of elongation of segments of cold-hardened and unhardened coleoptiles.

Seasonal Changes in Rootability and Rooting Substances of Picea glauca Cuttings1

Abstract Cuttings of Picea glauca (Moench) Voss rooted poorly from October to January and improved thereafter with the best rooting in April. The acidic fraction of methanol extract from P. glauca showed root-promoting activity by the mung bean cuttings bioassay and growth inhibiting activity by the wheat coleoptiles bioassay. Both activities were strongest in November. There was no apparent causal relationship between the acidic fraction and the rooting of P. glauca cuttings. The activity of water soluble rooting substance(s) was high in October, dropped suddenly in November, and rose slowly after November and rapidly after March. There was an apparent parallel correlation between the rooting of P. glauca cuttings and the activity of water soluble rooting substance(s). The acidic root-promoting growth inhibitor was purified with paper chromatography, column chromatography, thin-layer chromatography, and gas-liquid chromatography, and its major component was tentatively identified as abscisic acid.

Effects of Adenine, Adenosine-3',5'-Cyclic Monophosphate, Guanosine, and Guanosine-3',5'-Cyclic Monophosphate on Wheat Coleoptile Segment Growth

Effects of Adenine, Adenosine-3',5'-Cyclic Monophosphate, Guanosine, and Guanosine-3',5'-Cyclic Monophosphate on Wheat Coleoptile Segment Growth

Importance of Time after Excision and of pH on the Kinetics of Response of Wheat Coleoptile Segments to Added Indoleacetic Acid

Segments of coleoptiles of 3-day-old wheat (Triticum x Aestivum L. cv. Kharkov M.C. 22) grown at 24 C were strung on a glass rod and the kinetics of their elongation in 0.01 m K-phosphate buffer was examined photometrically. Measured rates of elongation in response to treatments were corrected by subtraction of endogenous rates. The customary practice of testing the effects of growth regulators added between the two endogenous surges of growth, that is, up to 3 hours after segments were excised from coleoptiles, gave erroneous kinetic data. Rates of response were then limited by the passive penetration of added auxin and the second endogenous surge interfered with late responses. It was necessary to wait for a phase of more rapid but more steady elongation after the second endogenous surge was over, about 4 hours for wheat at 25 C, to attain the active uptake required for nearly synchronous response through the segment. The more active uptake in this steady phase was confirmed with beta-[2-(14)C]indoleacetic acid and it was greater at pH 5 than at pH 7. The degree of dissociation of indoleacetic acid added at pH 7 was an impediment to penetration that could be compensated for by removal of intercellular air. The pH did not influence the endogenous rate of elongation. The dependence of the rate of elongation on the concentration of indoleacetic acid added at pH 5 was bell-shaped with maximum rate at 10 mum indoleacetic acid, in confirmation of previous measurements made over long intervals of time. The relation between the response and suboptimal concentrations was not sigmoid but was indicative of greater binding affinity than previously reported.