. Agricultural botany, theoretical and practical. Botany, Economic; Botany. ' SMUT ' OF OATS 717 healthy, the straw very rarely showing any evidence of ' smut.' It is generally observed that when one ear is destroyed, all the others produced by the same plant are similarly injured. ' Smut' is known in some localities as ' dust-brand,' and 'chimney-sweeper,' and in former times frequently destroyed from 30 to 50 per cent, of the oat crop on some farms. Cause.—The ' smut' or sooty powder is composed of thousands of chlamydospores of the fungus Ustilago avems Jens. Each chlamydospore (Fig. 240) i
. Agricultural botany, theoretical and practical. Botany, Economic; Botany. ' SMUT ' OF OATS 717 healthy, the straw very rarely showing any evidence of ' smut.' It is generally observed that when one ear is destroyed, all the others produced by the same plant are similarly injured. ' Smut' is known in some localities as ' dust-brand,' and 'chimney-sweeper,' and in former times frequently destroyed from 30 to 50 per cent, of the oat crop on some farms. Cause.—The ' smut' or sooty powder is composed of thousands of chlamydospores of the fungus Ustilago avems Jens. Each chlamydospore (Fig. 240) is round or oval in form and possesses a thick, dark, olive- brown outer coat which is slightly rough, and a thin transparent inner one. When placed in water, after resting through winter the spores readily ger- minate and each gives rise to a short hypha, or conidiophore which is often termed a promvceliuni. The latter is divided into cells by four or five transverse septa, and from it are produced small transparent conidia, one from each cell as at b, Fig. 240. When these fall off others are pro- duced from the same cells of the promyceliura. In ordinary water the conidia give rise to delicate germ-tubes {d), but in water from dung-heaps and in solutions of nutrient materials generally, they multiply rapidly for a time by ' budding' (e); after the superabundant food is diminished, each conidium formed in the ' budding ' process may develop a germ-tube. Although the chlamydospores from diseased ears are blown on to the leaves of surrounding healthy plants, they do not spread. Fig. 240.—s Chlamydospores of oat-smut, Ustilago avents Jens.; a conidiophore with conidia b; c detached conidia; d conidia germinating in water ; e ' budding' of the conidia as seen when the latter are grown in nutrient solutions (enlarged about 500 diameters).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and a
Size: 2077px × 1203px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
