Botany; Geotropism; Plants -- Irritability and movements
Squares of card were attached to one side of the tips of 11 radicles
within the same jars in which the above trials were made, and five of
them became plainly, and one slightly, curved away from this side.
Other
analogous cases will be immediately described. The fact is here
mentioned because it was a striking spectacle, showing the difference
in the sensitiveness of the radicle in different parts, to behold in
the same jar one set of radicles curved away from the squares on their
tips, and another set curved towards the squares attached a little
higher up. Moreover, the kind of curvature in the two cases is
different. The squares attached above the apex cause the radicle to
bend abruptly, the part above and beneath remaining nearly straight; so
that here there is little or no transmitted effect. On the other hand,
the squares attached to the apex affect the radicle for a length of
from about 4 to even 8 mm., inducing in most cases a symmetrical
curvature; so that here some influence is transmitted from the apex for
this distance along the radicle.
Pisum sativum (var. Yorkshire Hero): Sensitiveness of the apex of the
Radicle.—Little squares of the same card-like paper were affixed (April
24th) with shellac to one side of the apex of 10 vertically suspended
radicles: the temperature of the water in the bottom of the jars was
60°–61° F. Most of these radicles were acted on in 8 h. 30 m.; and
eight of them became in the course of 24 h. conspicuously, and the
remaining two slightly, deflected from the perpendicular and from the
side bearing the attached squares. Thus all were acted on; but it will
suffice to describe two conspicuous cases. In one the terminal portion
of the radicle was bent at right angles (A, Fig. 66) after 24h.; and in
the other (B) it had by this time become hooked, with the apex pointing
to the zenith. The two bits of card here used were .07 inch in length
and .04 inch in breadth. Two other radicles, which after 8 h. 30 m.
were moderately deflected, became straight again after 24h. Another
trial was made in the same manner with 15 radicles; but from
circumstances, not worth explaining, they were only once and briefly
examined after the short interval of 5 h. 30 m.; and we merely record
in our notes “almost all bent slightly from the perpendicular, and away
from the squares; the deflection amounting in one or two instances to
nearly a rectangle.” These two sets of cases, especially the first one,
prove that the apex of the radicle is sensitive to slight contact and
that the upper part bends from the touching object. Nevertheless, on
June 1st and 4th, 8 other radicles were tried in the same manner at a
temperature of 58°–60° F., and after 24 h. only 1 was decidedly bent
from the card, 4 slightly, 2 doubtfully, and 1 not in the least. The
amount of curvature was unaccountably small; but all the radicles which
were at all bent, were bent away from the cards.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account