Both micro- and macroalgae have long been used to augment plant productivity and food production in various regions of the world through their beneficial effects when applied to soils. Interactions of algae with the soil community undoubtedly are complex and benefits are dependent on the crop and the local environmental conditions. This has resulted in much speculation as to mechanisms involved as well as the validity of the results reported. It is now 60 years since the first commercial seaweed extract was manufactured for agricultural use. These aqueous extracts allowed for the first time the direct application of soluble seaweed constituents to specific plant organs such as leaves and roots. The earlier concept that benefits of seaweeds and their extracts were due mainly to their manurial value or to their micronutrient suites is no longer tenable. Seaweeds likewise have been used for millennia as fodder supplements to improve animal nutrition and productivity. Recent research is focusing on their mode of action, specific health benefits, and the mechanisms of action in animals. Improved analytical techniques and instrumentation coupled with the use of molecular genetic tools are establishing that seaweed extracts can modify plant and animal responses at a fundamental level. It therefore seems appropriate to review key developments over the years and to remark on novel findings. A new and exciting vista has opened for seaweed extracts in both plant and animal applications.

Seaweed extract stimuli in plant science and agriculture

THE FIRST of this group of papers (Steward et al., 1958) described the various ways in which freely suspended cells from certain dicotyledonous plants grow and multiply to form a relatively unorganized nmulticellular mnass. The growth in question occurs under prescribed and controlled nutritional and environmental conditions. The purpose of this paper is to show hoAv the growth may be carried forward into the formation of roots and shoots and, in fact, the development of whole plants.

GROWTH AND ORGANIZED DEVELOPMENT OF CULTURED CELLS. II. Organization in Cultures Grown from Freely Suspended Cell

Coconut water (coconut liquid endosperm), with its many applications, is one of the world's most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.

/pdf/the-chemical-composition-and-biological-properties-of-3d8v1ttk6r.pdf

The Chemical Composition and Biological Properties of Coconut (Cocos nucifera L.) Water

Despite long-standing observations on diverse cytokinin actions, the discovery path to cytokinin signaling mechanisms was tortuous. Unyielding to conventional genetic screens, experimental innovations were paramount in unraveling the core cytokinin signaling circuitry, which employs a large repertoire of genes with overlapping and specific functions. The canonical two-component transcription circuitry involves His kinases that perceive cytokinin and initiate signaling, as well as His-to-Asp phosphorelay proteins that transfer phosphoryl groups to response regulators, transcriptional activators, or repressors. Recent advances have revealed the complex physiological functions of cytokinins, including interactions with auxin and other signal transduction pathways. This review begins by outlining the historical path to cytokinin discovery and then elucidates the diverse cytokinin functions and key signaling components. Highlights focus on the integration of cytokinin signaling components into regulatory networks in specific contexts, ranging from molecular, cellular, and developmental regulations in the embryo, root apical meristem, shoot apical meristem, stem and root vasculature, and nodule organogenesis to organismal responses underlying immunity, stress tolerance, and senescence.

/pdf/cytokinin-signaling-networks-3428h56930.pdf

Cytokinin Signaling Networks

Neurospora. ii. methods of producing and detecting mutations concerned with nutritional requirements

WHILE ATTEMPTING to induce artificial parthenogenesis by inj ecting physiologically active substances into unfertilized ovaries of Datura stramonium (16) it was realized that some of these substances might never penetrate the ovules far enough to reach the egg cell. With this in mind experiments were planned by which the development of the egg cell and the subsequent parthenogenetic embryo, should such be obtained, could take place in vitro. In order to accomplish this, two major steps are necessary: (a) division of the egg cell must be induced, and (b) development of the resulting embryo into a viable plant must be accomplished. It seemed obvious to try to control step (b) before attempting (a). The present paper deals with step (b), the culture of small embryos in vitro. Successful culture of embryos has been reported in the literature (10, 14, 20). For a review of the literature, see LaRue (10) and White (19). The media used by the different authors vary considerably. Tukey (14) concluded that there was no appreciable difference in effect between the different salt solutions used by various workers. The concentration, too, could be varied from one to ten times without much effect. It seems clear, however, that the necessity of adding organic substances to the medium greatly depends upon the stage at which the embryos are isolated. Thus mature embryos can be grown in a strictly inorganic medium. The addition of sugar even retards their growth (14). Nearly mature embryos require sugar (10, 14). According to Tukey, the younger stages require more than the older ones. Still younger embryos require, in addition to sugar, the heat stable factors found in yeast extract or fibrin digest (10, 20). LaRue employed indoleacetic acid in low concentrations to replace yeast extract in his media. Although the embryos successfully cultured by the authors mentioned above were often very immature, they still were isolated at a relatively advanced stage of development. LaRue (10), who successfully grew the embryos of a large number of species, makes the following statement: ". . . embryos 0.5 mm. or slightly less in length can be grown successfully . . . those of still smaller size have not yet been brought under control. . . . at a length of 0.5 mm. we may have reached a new lower threshold which will be difficult to pass." It is well to remember that the actual size of an embryo is not a measure of the stage of development in different species. Thus an embryo 0.5 mm. long of a plant having relatively large embryos, such as Datura, will be in a much earlier stage of development than an embryo of the same length of a plant such as Nicotiana, which has minute embryos. White (20) isolated young heart-shaped embryos from Portulaca. These embryos grew from 0.12 to

Cultivation in vitro of small datura embryos

An analysis of the function of the leaf in the process of root formation in cuttings

THE CLASSICAL concept of water uptake into cells by means of osmosis is so universally accepted that it is often regarded more as a fact than a convenient theory. Root pressure also is often considered to be entirely osmotic in nature (Sabinin, 1925; Crafts and Broyer, 1938). However, experiments are known which make it appear as if osmosis is inadequate to explain the water uptake of cells. Ursprung and Blum's experiments (1921, 1925) seem to show that water uptake by the cells of the endodermis is possible against an osmotic gradient. Bennett-Clark and Bexon (1940) have experiments which tend to show that the "water absorbing power" of the leaf cells exceeds the osmotic pressure of the vacuole. Heyl (1933) concluded from a study in which he investigated the effect of temperature upon the rate of bleeding and the rate of backward movement of the exudate under influence of plasmolytica, that the mechanism of bleeding cannot be exclusively osmotic in nature. The purpose of this investigation was to find out experimentally whether or not osmosis alone is capable of explaining root pressure. In order to do this, a simple basic experiment was designed by which it was possible to measure (A) the osmotic pressure of the exudate2 and (B) the pressure with which water is taken up by the roots. If these two values are equal in magnitude, root pressure can be explained on the basis of osmotic pressure alone. If the pressure with which water is taken up by the roots (root pressure) is larger than the osmotic pressure of the exudate, then root pressure is due to other causes in addition to osmosis.3 The root pressure was determined as the osmotic pressure of a mannitol solution which exactlv compensated the root pressure. TEcHNIQuE.-Seeds of "San Jose Canner" tomatoes were sown in sand in flats and watered with Hoagland solution. After the seedlings were six to eight weeks old, they were transferred to culture solutions with forced aeration in one of the air-conditioned greenhouses (26.50C. and 70 per cent humidity). For constancy of temperature and other properties of these greenhouses, see Went (1942). In order to avoid "shock" reactions the experiments (with the exception of the one mentioned in fig. 3) were carried out at the same constant conditions as those under which the plants were grown. The in1 Received for publication April 18, 1942. 2 The nomenclature regarding osmotic quantities proposed by Meyer (1938) and Meyer and Anderson (1939) is used throughout. Therefore "osmotic pressure" of the exudate denotes "osmotic value" or "osmotic concentration" of the older literature. 3 It is assumed that the osmotic pressure of the exudate equals, or at least is not higher than, that of the contents of the vessels down in the water-absorbing region of the roots. Evidence for the correctness of this assumption is given later in the paper. dividual plants were held with non-absorbent cotton in paraffined wooden lids, which were placed on onegallon mayonnaise jars which were painted white over a black undercoat and filled with Hoagland solution (Hoagland and Arnon, 1938). In order to obtain plants rich in carbohydrates which would be capable of carrying on metabolism for a considerable time after they were decapitated, the nutrient solution was not renewed, but the water lost by transpiration was replaced by distilled water. In this way low-salt plants which are rich in carbohydrates (Hoagland and Broyer, 1936; Grossenbacher, 1938) were obtained. The pH was adjusted periodically and maintained between 5 and 6, and ferric chloride was added weekly. The Hoagland solution was renewed in a few special experiments which will be mentioned later. In the experiments mentioned in the last section, dealing with the effects of KCN, a nutrient solution suggested by Arnon and Hoagland (1940, p. 477) was employed. Exceptional root growth was obtained in this solution and the pH adjustments were not necessary. Iron citrate was given twice weekly. After the plants had grown from four to seven weeks in the culture solution, they were cut about one to two inches above the uppermost roots. This decapitation was done about noon, because it was found that plants cut earlier in the day often did not bleed at all, even when left for a day or longer. After decapitation the plants were transferred to distilled water. In some experiments distilled water was put in the culture jars a few days before the plants were decapitated (fig. 1). The root system was put in distilled water because it eliminates accumulation of solutes as a complicating factor in the process of exudation; it also increases the rate of exudation over that of root systems kept in nutrient solution. In some experiments (fig. 2) the roots were kept in a full-strength Hoagland solution instead of in water. This did not influence the results, however. It only caused a slower rate of exudation and a higher osmotic pressure of the exudate. During the experiments, as well as during the growing period, forced aeration was used continuously. The stump of the plant was attached to a thickwalled U-tube with narrow bore, by means of a small piece of rubber tubing firmly attached to the stump with string. In this manner a perfectly water-tight connection was obtained which allowed the U-tube to be interchanged conveniently for a horizontal "potometer" tube (for rate determinations). The majority of plants bled profusely, often at a rate of 2 cc. per hour. After a minimum of 2 cc. of the exudate was collected for freezing point determinations, the U-tube was replaced by a horizontal thick-walled tube (inside diameter 0.042 inches). The meniscus moved rapidly outward.

Water uptake by excised root systems of the tomato due to non-osmotic forces

http://www.plantphysiol.org/content/plantphysiol/15/2/291.full.pdf

Auxin in marine algae.

JUST AS the production of polyploid plants by the colchicine technique has proven of value in plant breeding, so the discovery of a method for producing haploids at will would also be a useful tool. Since the haploids which occur spontaneously'in nature probably arise through reduced parthenogenesis, this would seem to be the most likely means of attaining the desired result. If this procedure could be carried out by artificial methods, such as chemical treatment, a new way would be available for establishing pure lines. Thus a 2n plant could be treated to yield a In plant bearing only maternal characteristics. The chromosome number of this plant could then be doubled by colchicine treatment, producing a plant which would breed true. With this in mind, a study of the effect of various chemicals in stimulating fruit, seed and egg-cell development was made in order to survey the possibilities of producing haploid plants by artificial treatment. Many inorganic and organic chemicals, including plant hormones such as auxins,2 traumatic acid, biotin and pantothenic acid, were injected into the ovaries of plants to observe their effect. Although pseudoembryos were obtained in Datura after auxin treatment, no true embryos resulted from any chemical tested. As a result of observations made in these experiments, combined with information obtained by a survey of the literature on parthenogenesis, haploidy, pseudogamy and related subjects, a working hypothesis of fruit and seed development has been suggested. MATERIALS AND METHODS.-A 4n strain of fieldgrown Melandrium dioicum and both 2n and 4n strains of Datura stramonium were used as test plants. Datura was chosen because detailed information concerning its characteristics is available. Melandrium was chosen because it is dioecious, and because of the nature of the ovary which, with its central placentation, surrounded by a large empty space, greatly facilitates injection with various solutions or emulsions. Flowers to be treated were cut just above the ovary when the buds were about to open. In this way the styles were removed, and in the case of Datura, the anthers also, thus preventing stray pollination. Immediately thereafter the ovaries were injected, by means of a hypodermic syringe, with the various chemicals. Since the Datura ovaries are quite solid and divided into four locules, injections were made through the side of the ovary wall in two to four places. In Melandrium, injections in the side of the ovary proved somewhat injurious to the fruit, frequently causing fungal infection. Infections were avoided by making injections through the top of the 1 Received for publication April 28, 1941. 2 Any substance causing cell elongation in the Avena test is by definition [66] an auxin. ovary. One hole was made to allow air to escape, and another for the inj ection, thus filling the entire space around the ovules with solution. The chemicals were tested in a wide range of concentrations. For each concentration a minimum of ten ovaries was treated. Only the auxins naphthaleneacetic acid and indolebutyric acid prevented abscission of the fruit. Since fruit retention is essential to a further study of the effect of treatment, it was the usual practice to inject a solution of auxin in combination with any other substance to be tested. In order to increase the solubility of the auxins they were converted to their ammonium salts by adding a few drops of dilute ammonium hydroxide until they dissolved. A stock solution of one per cent in distilled water was diluted to give solutions of the desired strength. Auxins were also applied in the lanolin emulsion made with morpholine which has been used successfully as a vehicle for colchicine [62]. A 0.1 per cent auxin-lanolin-emulsion was obtained by adding one volume of stock auxin solution to nine volumes of plain emulsion. The emulsion was applied internally as well as externally by using a regular hypodermic syringe. OBSERVATIONS.-Auxin treatment of Melandrium. -When the styles of Melandrium are removed as outlined above, but not injected with auxins, the ovaries abscise within a few days. Naphthaleneacetic acid, indolebutyric acid, and indoleacetic acid separately and in combinations were injected into Melandrium ovaries in concentrations ranging from 0.000001 per cent to 1.0 per cent. Injection of 0.1 per cent naphthaleneacetic acid into the ovaries gave by far the best results, at least 90 per cent of the ovaries of Melandrium so treated yielding parthenocarpic fruits. Lower concentrations resulted in a very high percentage of abscissions, whereas higher concentrations damaged the ovaries. The size of such parthenocarpic fruits was approximately the same as that of fruits obtained by normal pollination. Indolebutyric acid gave fairly good results but not as good as naphthaleneacetic acid. Indoleacetic acid failed to give satisfactory results, perhaps because it is less stable than naphthaleneacetic acid. Experiments were undertaken to find out whether the auxins could be applied externally, thus preventing injuries from the injections. Emulsions containing auxins (usually naphthaleneacetic acid) were therefore applied, (a) on the peduncle, just below the flower, (b) on the outside of the ovary, (c) in the ovary by injection. The average outside dimensions of fruits resulting from these treatments were nearly the same (fig. 1; table 1). However, when they were opened, great differences were found (fig. 1; table 1). Whereas in ovaries that had been treated externally, the placenta and the ovules had hardly en-

Chemical stimulation of ovule development and its possible relation to parthenogenesis

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