What is "geotropism"

Usage examples of "geotropism".

We may therefore conclude that the initial power of an irritant on the apex of the radicle of the bean, is less than that of geotropism when acting at right angles, but greater than that of geotropism when acting obliquely on it.

With the pea, therefore, the irritation from an attached object, and from geotropism when acting at right angles to the radicle, are nearly balanced forces.

The fact of tubers being formed by the foregoing three widely distinct plants, makes us believe that their protection from animals at an early age and whilst tender, is one at least of the advantages gained by the remarkable elongation of the petioles of the cotyledons, together with their power of penetrating the ground like roots under the guidance of geotropism.

The tips of the radicles were placed so as just to touch the upper end of the glassplates, and, as they grew downwards they pressed lightly, owing to geotropism, on the smoked surfaces, and left tracks of their course.

In coming to a conclusion with respect to the effects of cauterising the tips of these radicles, we should bear in mind, firstly, that horizontally extended control radicles were always acted on by geotropism, and became somewhat bowed downwards in 8 or 9 h.

In those cases in which radicles with attached filaments were placed so as to stand up almost vertically, they curved downwards through the action of geotropism, circumnutating at the same time, and their courses were consequently zigzag.

The capsules and flowerheads of some plants are bowed downwards through geotropism, and they then bury themselves in the earth for the protection and slow maturation of the seeds.

As this latter movement occurred in complete darkness, and with peduncles arising from upright and from dependent branches, it cannot be due to apheliotropism or to epinasty, but must be attributed to geotropism.

Uncauterised specimens similarly placed became much bent downwards through geotropism in the course of 5 or 6 hours.

Vicia faba, circumnutation of radicle, 29, 30 --, of epicotyl, 3133 --, curvature of hypocotyl, 92 --, sensitiveness of apex of radicle, 132134 --, of the tips of secondary radicles, 154 --, of the primary radicle above the apex, 155158 --, various experiments, 135143 --, summary of results, 143151 --, power of an irritant on, compared with that of geotropism, 151154 Vicia faba, circumnutation of leaves, 233235 --, circumnutation of terminal leaflet, 235 --, effect of apogeotropism, 444 --, effect of amputating the tips of radicles, 523 --, regeneration of tips, 526 --, short exposure to geotropic action, 527 --, effects of amputating the tips obliquely, 528 --, of cauterising the tips, 529 --, of grease on the tips, 534 Vines, Mr.

This apparently was due to epinasty and not to apogeotropism, for the apex, soon after passing the perpendicular, curved so rapidly downwards that we could not doubt that the movement was at least aided by geotropism.

Means of observation Apogeotropism--Cytisus--Verbena--Beta--Gradual conversion of the movement of circumnutation into apogeotropism in Rubus, Lilium, Phalaris, Avena, and Brassica--Apogeotropism retarded by heliotropism--Effected by the aid of joints or pulvini--Movements of flowerpeduncles of Oxalis--General remarks on apogeotropism--geotropism--Movements of radicles--Burying of seedcapsules--Use of process--Trifolium subterraneum--Arachis--Amphicarpaea--Diageotropism--Conclusion OUR object in the present chapter is to show that geotropism, apogeotropism, and diageotropism are modified forms of circumnutation.

The benefits derived from geotropism, apogeotropism, and diageotropism, are generally so manifest that they need not be specified.

Considering the several facts given in this chapter, we see that the course followed by a root through the soil is governed by extraordinarily complex and diversified agencies,--by geotropism acting in a different manner on the primary, secondary, and tertiary radicles,--by sensitiveness to contact, different in kind in the apex and in the part immediately above the apex, and apparently by sensitiveness to the varying dampness of different parts of the soil.

We will therefore speak of circumnutation, which is always in progress, as modified by epinasty, hyponasty, geotropism, or other agencies, whether internal or external.