Clifford J. Pollard

Soluble carbohydrates of dry and developing seeds

Abstract Sucrose was present in seeds of 31 species at all ages and stages of their development. The raffinose family of oligosaccharides is present in most mature and dry seeds; tomato and tobacco seeds contain planteose, whereas sesame seeds contain this sugar and a higher member of the planteose series. Cotton seeds contain raffinose, stachyose, verbascose and an unidentified ketose. Free monosaccharides were not detected in any of the dry seeds; although free glucose and fructose were detected in some immature seeds, these sugars decreased in amount and eventually disappeared during seed maturation. Sucrose, stachyose, raffinose and verbascose accumulated, in developing soybeans, in that sequence. Maltose, a sugar rarely found in plant tissues, is present in immature soybean and honey locust seeds but does not occur in the other seeds examined. It increases to a maximum during development, subsequently decreases in amount during maturation and ripening and eventually disappears completely. The petioles of old leaves and stems of the soybean plant contain maltose, but the petioles of young soybean leaves, empty pods, leaf blades and roots do not.

Fructose oligosaccharides: Possible markers of phylogenetic relationships among dicotyledonous plant families

Abstract Stems from more than 555 species representing 440 genera of approximately 210 dicotyledonous families were surveyed for the presence of fructose oligosaccharides. The tissues from 372 species representing 312 genera and 187 families did not contain such oligosaccharides. The sugars occurred sporadically or in small amounts in members of the following families: Crossosomataceae, Lauraceae, Malpighiaceae, Cornaceae, Myrisinaceae, Melianthaceae, Greyiaceae, and Simaroubaceae. The fructosyl sucrose trisaccharide, isokestose, aswell as its fructose tetrasaccharide homolog (but not higher inulin oligosaccharides) were present in members of the families Hippocastanaceae and Limnathaceae. Stems from members of the families Clethraceae and Monotropaceae, and some members of the Polemoniaceae, contained two series of fructose oligosaccharides: one based on isokestose (the inulin series) and the other one based on kestose (the levan series). The inulin or isokestose-based series of fructose oligosaccharides, alone, was present in members of the following families: Menyanthaceae, Boraginaceae, Campanulaceae, Goodeniaceae, Stylidiaceae, Brunoniaceae, Calyceraceae and Compositae. The primary metabolites occur ubiquitously and consistently in tissues of plants of these families. We hypothesize that this conservative character represents several phylogenetic alliances among them.

Early effects of gibberellic acid on barley aleurone layers

Abstract The most obvious effects resulting from the application of the hormone gibberellic acid (GA) to cereal aleurone layers are the secretion of metabolites and the de novo synthesis and secretion into the medium of enzymes, mostly hydrolases ( Varner, 1964 ; Varner et al., 1965 ; Chrispeels and Varner, 1967 a,b ; Jacobsen and Varner, 1967 ). For that reason research on the mode of action of GA has focused on the elucidation of the roles of protein synthesis and RNA synthesis in the responses. The present report follows observations that the effects of GA occur sequentially ( Pollard, 1968 ). Furthermore, we have found that GA enhances the secretion of more than 20 metabolites and enzymes. It is desirable to identify the earliest of these reponses since they are most likely to be near the primary action of the hormone. We wish to report (1) the effect of GA on the secretion of soluble carbohydrates and several phosphatases, the earliest effects it has been possible to detect and (2) data relating the effects of the hormone to other aspects of metabolism, especially protein synthesis, RNA synthesis and respiration.

THE DEOXYRIBONUCLEIC ACID CONTENT OF PURIFIED SPINACH CHLOROPLASTS.

Abstract Chloroplasts isolated from spinach leaves in aqueous media and purified by a variety of techniques were found to contain DNA. Identification of the DNA was based on its chemical properties and on the absorption spectra of the reaction products of the material with diphenylamine, cysteine-sulfuric acid, and indole. Values of 1.3–7.1 μg. of DNA per milligram of protein were found; however, values of 3–4 μg. DNA per milligram protein were typical.

Rapid gibberellin responses and the action of adenosine 3',5'-monophosphate in aleurone layers.

Abstract 1. 1. Studies on the biological significance of the effects of adenosine 3′,5′-monophosphate (cyclic AMP) and their relation to the responses mediated by gibberellic acid in cereal grains are reported. Increased secretion of soluble sugar by barley (Hordeum vulgare cv. Betzes) aleurone layers within 15 min after applying cyclic AMP or gibberellic acid may be realized if the cells are washed prior to treatment. 2. 2. Although cyclic AMP alone can effectively mimic gibberellic acid, even in causing the synthesis and secretion of amylase, this effect of the nucleotide is only realized sporadically. 3. 3. The responses obtained by treating barley or wheat (Triticum aestivum cv. Genesee) layers with suboptimal concentrations of gibberellic acid are potentiated consistently by treating the tissue simultaneously with cyclic AMP. Similarly, layers that are pretreated with suboptimal concentrations of the hormone, washed and then treated either with higher concentrations of the hormone or with cyclic AMP respond rapidly by secreting increased amounts of metabolites and enzymes into the medium. The potentiation is specific for cyclic AMP, among the nucleotides; its dibutyryl derivative being more active than the parent compound. 4. 4. Adenosine was th eonly radioactive product detected in the medium after incubation of labelled cyclic AMP with barley layers. It is concluded that some criteria for a biologically significant involvement of cyclic AMP in layers have been met. It is postulated, however, that cyclic AMP does not substitute entirely for the growth factor by probably acts by potentiating the responses that are initiated by the hormone.

Fructose oligosaccharides in monocotyledons: A possible delimitation of the order liliales

Abstract Stems from 198 species representing 165 genera of 46 monocotyledonous families were examined for the presence of fructose oligosaccharides. Aside from occurring in the subfamily Festucoideae of the Poaceae, in Cyperaceae and in Zostera marina of the Zosteraceae, the sugars were found exclusively in some closely related liliaceous families. These are the Agavaceae, Alstromeriaceae, Amaryllidaceae, Cyanastraceae, Haemodoraceae, Iridaceae, Liliaceae, Ruscaceae and Xanthorrhoeaceae. On the other hand, the fructosides were not detected in representatives of certain families whose placement in the order Liliales is controversial or dubious. These are the Dioscoreaceae, Philesiaceae, Philydraceae, Pontederiaceae, Smilacaceae, Stemonaceae, Taccaceae and Velloziaceae. These findings support the assertion of some systematists that these latter families should perhaps not be placed in the order.

Initiation of response in aleurone layers by gibberellic acid

Abstract A new procedure for studying the action of gibberellic acid in barley (Hordeum vulgare cv. Betzes) aleurone layers was utilized. Exposure of the layers to gibberellic acid for short periods of time followed by through washing and subsequent incubation in the absence of the phytohormone resulted in increased secretion of enzymes and metabolites. Increased secretion of soluble of soluble sugar (a typical hormonal response) by such treated and washed layers was linearly proportional to the time of exposure as well as to the concentration of hormone in the exposure medium. It was decreased by exposure under anaerobic conditions and was affected by the temperature of exposure. The hormone disappears from the medium during exposure but the results suggest that some of it can be removed from the layers by washing. Since cycloheximide and abscisic acid inhibited hormone-induced secretion when they were applied simultaneously and continuosly with gibberellic acid but had no effect on pretreated layers whereas secretion was inhibited by anaerobiosis in both instances, at least two steps appear to be involved in hormonal action on secretion.

The metabolism of galactose and the raffinose oligosaccharides by germinating bambarra groundnut seeds

Abstract Stachyose is present in the highest amount in the soluble sugar fraction of dry bambarra groundnut cotyledons, followed in descending order by raffinose, sucrose and verbascose. During germination in the dark, the stachyose and raffinose content decrease rapidly, but there is little change in the relatively small amount of verbascose present. The sucrose content increases rapidly during the first two weeks and decreases thereafter. Free glucose and fructose were present in the cotyledons after the 7th day and gradually increased in amount with time of germination. Free galactose and other galactose-containing oligosaccharides were not detected in either the dry or germinated bambarra seeds. During germination, galactose was the only identifiable sugar, aside from traces of sucrose, glucose and fructose, in the extracted soluble sugar fraction in the embryonic axes of all ages when the tissue was incubated with D-[1 14 C] galactose. With the cotyledons, however, most of the radioactivity was in glucose and fructose during the early period of germination and in sucrose later. A small fraction of the radioactivity was lost as CO 2 .

Apparent distinctiveness of the actions of gibberellic acid in aleurone layers

Abstract The relationship of some of the many responses that are induced by gibberellic acid in barley (Hordeum vulgare var. Betzes) was investigated by comparing how some enzymes whose secretion is elicited by the hormone were affected, quantitatively, by various treatments. The effect of heating half seeds at 55° for varying short periods prior to treatment with the hormone as well as the effects of cycloheximide, of dinitrophenol and of abscisic acid on the relative amounts of various enzymes secreted in the presence of the growth factor were observed. All of the hormonal responses were affected differently by all of the diverse treatments. Since the patterns of inhibition and of stimulatin exhibited by the responses were clearly dissimilar, it appears that the hormonal actions on the enzymes are distinct.