. Introduction to botany. Botany. SEEDS AND SEEDLINGS 165 the cotyledons remain underground, inclosed in the seed coats, and gradually empty their stores of reserve food into the growing seedling. In the bean the cotyledons come out of the ground but never become leaf-lilte, while in the squash, castor bean, buckwheat, and morning-glory (fig. 144) they emerge from the ground and become short-lived lea^'es. 157. Reserve food of seeds digested by enzymes. One of the most surprising thmgs about the early growth of seedlings is the rapid way in wliich many kinds begin to grow even m sawdust or on
. Introduction to botany. Botany. SEEDS AND SEEDLINGS 165 the cotyledons remain underground, inclosed in the seed coats, and gradually empty their stores of reserve food into the growing seedling. In the bean the cotyledons come out of the ground but never become leaf-lilte, while in the squash, castor bean, buckwheat, and morning-glory (fig. 144) they emerge from the ground and become short-lived lea^'es. 157. Reserve food of seeds digested by enzymes. One of the most surprising thmgs about the early growth of seedlings is the rapid way in wliich many kinds begin to grow even m sawdust or on moist blotting paper. Evidently the plant food must all come from the seed in the begmning, and the removal of most of the reserve food of the seed greatly retards the growth of the seedling (fig. 14(3). It is not at once clear how the proteins and the starch of some seeds and the oil or cellulose of others are so quickly withdrawn from them and transferred to the growing plantlet. ]Most of the reserve substances found in seeds are difficultly soluble or quite insoluble in water or the watery sap of plants, but the msoluble substances, before being transferred into the seed- ling, are transformed into soluble ones. This is due to the action of certain substances known as enzymes or soluble fer- ments. An enzyme as found ia seeds is a substance secreted. Fig. 146. Pea seedlings growing in water A, deprived of l)otli cotyledons; B, with eotyledoBS uninjured. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917; Caldwell, Otis William, 1869- joint author. Boston, New York, [etc. ] Ginn and company
Size: 1010px × 2473px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisher, booksubjectbotany
