Endosperm sterol phenotype and germination in wheat

Free and conjugated sterols of endosperm, coats, scutellum, coleoptile and roots have been analysed at different germination stages in two wheat cultivars with different endosperm sterol phenotypes. It seems that sterol metabolism of the developing tissues, namely coleoptile and roots, is not affected by the sterol conjugation profile of the endosperm. Enough sterol is present in the mature embryo to supply the germinating axis during the observation period (144 hr at 16°). The data suggest that sterol is transferred from scutellum to coleoptile and roots during germinatio

The growth and respiration of the Avena coleoptile

In a previous paper (1) a relation was shown to exist between the respiration of the plant cell and its elongation under the influence of the plant growth hormone. A more extensive investigation of this relation was therefore undertaken with the hope that elongation would exhibit a close correlation with some relatively accessible property of the respiration, for example with the magnitude or the respiratory quotient of the latter. It may be said at once, however, that this was not the case, and that the work reported in the present paper, while revealing several points of interest and defining more clearly the dependence of elongation upon respiration, has not resulted in any explanation of the way in which respiration is essential to growth

Studies on the growth hormone of plants. VI. The distribution of the growth substance in plant tissues

1. It is shown that when plant tissues are ground with water the growth substance contained therein is inactivated by the oxidizing enzymes. 2. A simple method of extraction is described which enables the quantitative determination of growth substance in such tissues. 3. The amount and distribution of growth substance in the Avena coleoptile is determined by this method, and it is shown that while the substance does not diffuse out from the lower parts of the coleoptile, it is nevertheless present in considerable amounts, the concentration decreasing steadily with the distance from the tip. 4. Growth substance is also present in considerable amounts in Avena roots, and here also its concentration decreases steadily with distance from the tip. 5. The amount of growth substance diffusing out of root tips into dextrose agar, even during long periods of time, is not greater than the amount obtainable by direct extraction. Actual production in the root tip therefore either does not take place at all, or else takes place under quite different conditions from the production in the tip of the coleoptile

A deseeded Avena test method for small amounts of auxin and auxin precursors

In 1927 Went isolated the growth promoting hormone, auxin, from the tip of the Arena coleoptile, and worked out the now well known Arena test method for its quantitative determination. By the use of this method the chemistry and many phases of the physiological action of auxin have been studied. In physiological work, however, the amounts of hormone involved are frequently so small that quantitative or even qualitative work has often been very difficult or impossible. In this article is presented a supplementary procedure with deseeded Arena seedlings whereby smaller concentrations of the hormone not detectable by the standard method can be quantitatively determined. By the use of this method it has also been possible to demonstrate directly the existence of substances capable of being converted into auxin by the plant. Some data relative to the presence of a precursor of auxin in Arena and synthetic precursors of hereto-auxin are included

The action of the plant growth hormone

Although the control of cell elongation in plant tissues by a special growth-promoting substance or substances has been well established for some time, the processes by which this substance is able to bring about growth have remained obscure. Since the general properties of the response to growth substance by plant tissues, in particular of the Arena coleoptiles which have been most extensively studied, have been recently summarized by Thimann and Bonner (1933), only the principal points of interest for the present discussion need be given. These are briefly as follows: (a) The growth-promoting substance of the Avena coleoptile is produced only in the coleoptile tip and passes from there downward (Went, 1928). After removal of the tip new growth substance is formed by the uppermost cells of the stump ("physiological regeneration," Dolk, 1926). (b) The growth of the Avena coleoptile is for some time proportional to the amount of growth substance supplied to it (Thimann and Bonner, 1933). (c) The growth substance which enters the plant and causes growth cannot be recovered; i.e., is used up (Went, 1928). (d) Growth substance is an unsaturated acid of empirical formula C18H32O5 (Kögl, Haagen-Smit and Erxleben, 1933) and readily loses its growth-promoting activity by oxidation. (e) The growth substance is a true hormone, i.e., it acts in minute amounts and bears no direct stoichiometrical relationship to the number of molecules of soluble substance transformed during growth into, for example, cell walls. Thus one molecule of growth substance causes an amount of growth of the Avena coleoptile at 27°C. which requires the changing of 3 X 10^5 molecules of hexose to cellulose in cell walls (Thimann and Bonner, 1933). The changes in the physical properties of coleoptiles under the influence of growth substance have been studied to some extent. Heyn (1931), and independently, Söding (1931, 1932) have shown that the plasticity, and also to a considerable extent the elasticity, of the coleoptile is increased after action of growth substance, and that this increase is independent of whether growth has occurred or not; i.e., this action of growth substance is preliminary to active elongation. Heyn also found an increase in extensibility in coleoptiles which had been plasmolyzed after growth substance action, so that it is the physical properties of the cell wall, and not of the protoplasm, which are changed. The action of growth substance has now been further studied, and a few of the results will be described in the present paper. This study has been made easier by discovery of the fact that short sections of coleoptiles grow at a rapid rate if immersed in a growth substance solution of suitable concentration. This method of using coleoptiles is convenient because, under proper conditions, a large amount of growth takes place in a relatively short time, and the "physiological regeneration" mentioned in (a) occurs slightly or not at all. It has the added advantage that the effect of known concentrations of growth substance upon the growth of younger and older portions of the same coleoptile may be examined independently

Sprouting of oats: a new approach to quantify compositional changes

Background and objectives: The aim of this research was to gain a deeper insight into the effect caused by the addition of sprouted oat to food products. The effect of temperature and duration of the sprouting process was systematically studied by sprouting oat grains between 10 and 30°C for up to 3 days. Findings: Overall, it was found that temperatures between 20 and 25°C yield the most dramatic changes in the properties of sprouted oats. Based on the data, a simple system to characterize the sprouting progress by a visual inspection of the lengths of the coleoptile and radicles was developed. This degree of sprouting (DoS) was correlated with further grain properties. Conclusions: It was found that an exponential relationship between the DoS and grain properties existed. Furthermore, the observed increase in the reducing sugar content (up to 14.6 g/100 g) with increasing DoS was closely related to the increase in α‐amylase activity (up to 25 U/g). Significance and novelty: The good predictive power found indicates that the application of the concept degree of sprouting could develop into a reliable characterization method for sprouted grains usable for product development and specification.TU Berlin, Open-Access-Mittel - 201

Studies on the growth hormone of plants VII. The fate of growth substance in the plant and the nature of the growth process

Since the early work of Went (1928), it has been known that the growth substance of the Avena coleoptile may be obtained in the usual way, i.e. by diffusion into agar blocks, only from that part of the plant which produces it, namely the tip. The hormone is not recoverable in this way from those parts of the plant, such as the lower zones, which only make use of it. Recent work (Thimann, 1934) has, however, shown that by extraction with chloroform some growth substance is recoverable from the lower zones of the coleoptile. The results of this extraction method confirmed the earlier view that there is a marked concentration gradient of growth substance from tip to base

Concentration and localization of zinc during seed development and germination in wheat

In a field experiment, the effect of foliar Zn applications on the concentration of Zn in seeds of a bread wheat cultivar (Triticum aestivum L. cv. Balatilla) was studied during different stages of seed development. In addition, a staining method using dithizone (DTZ: diphenyl thiocarbazone) was applied to (1) study the localization of Zn in seeds, (2) follow the remobilization of Zn during germination, and (3) develop a rapid visual Zn screening method for seed and flour samples. In all seed development stages, foliar Zn treatments were effective in increasing seed Zn concentration. The highest Zn concentration in the seeds was found in the first stage of seed development (around the early milk stage); after this, seed Zn concentration gradually decreased until maturity. When reacting with Zn, DTZ forms a redcolored complex. The DTZ staining of seed samples revealed that Zn is predominantly located in the embryo and aleurone parts of the seeds. After 36 h of germination, the coleoptile and roots that emerged from seeds showed very intensive red color formation and had Zn concentrations up to 200 mg kg1, indicating a substantial remobilization of Zn from seed pools into the developing roots (radicle) and coleoptile. The DTZ staining method seems to be useful in ranking flour samples for their Zn concentrations. There was a close relationship between the seed Zn concentrations and spectral absorbance of the methanol extracts of the flour samples stained with DTZ. The results suggest that (1) accumulation of Zn in seeds is particularly high during early seed development, (2) Zn is concentrated in the embryo and aleurone parts, and (3) the DTZ staining method can be used as a rapid, semiquantitative method to estimate Zn concentrations of flour and seed samples and to screen genotypes for their Zn concentrations in seeds

Auxin-induced growth inhibition a natural consequence of two-point attachment

It is characteristic of a great number of biologically active substances that the responses which they elicit are twofold, low concentrations of the material promoting a particular activity, and higher concentrations inhibiting it. This is the case with the auxin-induced growth responses of plants. An active auxin such as indole acetic acid (IAA) brings about and is essential to growth in length of stems, hypocotyls and other plant organs including the Avena coleoptile