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The physiology and genetics of the pigments of barley (Hordeum volgare L)

University of British Columbia

1. The extraction and purification of anthocyanins from barley kernels presents problems not commonly encountered in other plant tissues. Special techniques using, for example, a pearler, sonic oscillator and alternate freezing and thawing of extracts have aided in the production of reasonably complete and pure anthocyanin and anthocyanidin extracts from chaff, pericarp and perisperm-spermoderm. Partial extraction of anthocyanin from the very proteinaceous aleurone layer of the grain was made possible by removing the dilute acid-water soluble fraction from the pearled aleurone tissue followed by acid-alcohol extraction. Extraction of anthocyanins from plant tissues presents little difficulty. 2. Paper chromatography has proven to be an excellent means of separating and partially characterizing anthocyanins and anthocyanidins in the barley soma and grain. Special techniques, such as the chromatostripe technique was developed, which greatly assisted the resolution of large quantities of anthocyanins. The Whatman No. 7 and No. 3 chromatographic paper greatly improved the resolution and reduced the trailing in comparison to Whatman No. 1 and No. 3 mm. commonly used in anthocyanin chromatography. Electrophoresis, too provided an excellent means for separating the yellow flavanoids from the anthocyanins. 3. A peeling technique was developed which greatly extended the possibilities of studying the anthocyanin development in the separate tissues of the caryopsis. This technique may also be of help to breeders and taxonomists in the accurate classification of barley. 4. Exploratory studies were undertaken on the pattern of distribution of anthocyanins in barley kernels of one white, three blue, two purple and two black verieties. Two anthocyanins "B" and "C" (probably cyanidin-3-glucoside) occured in one black (Gatami) and in the blues (Kwan, Montcalm and Trebi) and the purples (Gopal and Black Hulless). Additionally, of three anthocyanins found in the purple varieties, two "D" and "E" were common to both and one "F" was found in the variety, Gopal. Also found in the purple varieties was a poorly resolved group of "slow-moving" anthocyanins. The possible aglycones of these anthocyanins have been discussed. 5. These studies which represent the pigments of mature kernels (as a whole) were followed by the investigations on anthocyanins and anthocyanidins present in the separate tissues of the caryopsis viz. awns, hulls, pericarp, perisperm-spermo-derm and aleurone, at different stages of growth. Broad conclusions have emerged from these studies. Some anthocyanins, "fast-moving" under the conditions of chromatography of these investigations, hitherto, not detected in the mature tissues of the caryopsis, were present, in quantity, in the early stages of caryopsis development. In addition, the "slow-moving" anthocyanins, present in the mature kernels, could not be dectected in the early stages of caryopsis development. During later stages of caryopsis development, the "fast-moving" anthocyanins gradually disappeared and the "slow-moving appeared. In mature kernels of all the varieties studied, two antho-cyanidins, viz. delphinidin and cyanidin were present. Additionally, pelargonidin was present in the kernels of the purple varieties. During the developing stages of the kernel, however, only two anthocyanidins viz. cyanidin and pelargonidin were definitely present. Delphinidin could not be recovered. Similarly pelargonidin and cyanidin, hut not delphinidin, have been obtained from the maternal tissues such as the leaf sheath, awns, and pericarp of the barley plant. Delphinidin has been obtained only from the grain and may originate in the aleurone tissues or may come from leuco-anthocyanins; in colorless varieties, it is certain that the delphinidin comes from leuco-compounds but there is some reason to believe that in colored varieties some delphinidin may come from aleurone tissues. In the grain of blue varieties, delphinidin is relatively more abundant than cyanidin but, in purple varieties, the reverse appears to be true. Pelargonidin appears only in the purple varieties. 7. Leuco-anthocyanins which yield, on hydrolysis, cyanidin and delphinidin occur in the white barleys, such as Golden Pheasant, and in black barleys, such as Lion, which contain no anthocyanin. They may well occur with anthocyanins in the blue and purple barley varieties, but methods for their segregation have not been fully worked out. 8. Ocular studies on anthocyanins showed that color appeared in the awn tips about the time of meiosis. Other characteristic changes occurred in the pigment content during the transition from vegetative to reproductive stages. Field observations, then, led to the belief that there is some association of sexuality and anthocyanin development in barley.

Text

2012-01-17

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http://hdl.handle.net/2429/40107

Plant Science

University of British Columbia

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