Plant Transport and Physiology

Nastic movements are non-directional movements in which direction of response or movement is determined by the structure of responsive region. Nastic movement for instance, could be due to changes in the turgor pressure.

Seismonasty is defined as the nastic movement in response to shock, especially rapid folding of te leaflets of the sensitive plant due to changes in turgor pressure caused by vibration. It is also called as thigmonasty, because the external stimuli is touch.

Haptonasty or thigmonasty is the non-directional movement of a plant part in response to the touch of an object. The closing of the lamina of Venus fly trap is a type of haptonasty as a result of contact with an insect. If an insect happens to cross the lamina, the leaf will close quickly to prevent its escape. 

Nastic movements are responses of plant parts to stimuli. Seismonasty is the nastic response of a plant to touch or vibration. Dropping down of leaves of Mimosa pudica upon touching is due to seismonasty. Nyctinasty is the rhythmic nastic movement of plant in response to the onset of darkness. Chemonasty is the nastic response of a plant to external chemical. 

Nastic movement is the movement shown by plant part in response to environmental stimuli. This movement is repeatable and reversible. Examples include the folding of leaves of Mimosa pudica when touched. The folding and recoiling of leaves of Mimosa pudica in response to touch is called as thigmonastic movement.

Hygroscopic movement is that, which is caused by changes in moisture content of unevenly thickened cell walls. E.g., elators or the awns of the grains of some grasses. Also hygrometric movement, imbibitional movement.

Nastic movements are non-directional responses to stimuli and are usually associated with plants. The movement can be due to changes in turgor or changes in growth. Nastic movements differ from tropic movements in that the direction of tropic responses depends on the direction of the stimulus, whereas the direction of nastic movements is independent of the stimulus's position.

The free type of movements induced by some external stimuli like light, temperature, chemicals, etc are called as tactic movements. They are of three types: Phototactic, chemotactic and thermotactic.

The movement of chloroplasts in palisade cells in response to light is called as phototactic movement. Phototaxis is the movement of an organism in response to light; that is, the response to variation in light intensity and direction.

Growth movements are brought about by the unequal growth in different regions of the same organ. If shoot growth occurs at a faster rate alternately on right and left sides of the axis, resulting in a zig-zag axis, the movement is said to be nutation. When the leaves mature in growth and the flower buds open, more rapid growth occurs on the upper surface. This results in unfolding of coiled leaves and opening of the flowers. These are categorised under autonomic movement of growth.

Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by long, weak stems, smaller, sparser leaves due to longer internodes and a pale yellow colour called as chlorosis.  It increases the likelihood that a plant will reach a light source, often from under leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it.

Vernation is the formation of new leaves or fronds. Circinate vernation is the manner in which a fern frond emerges. As the fern frond is formed, it is tightly curled so that the tender growing tip of the frond is protected within a coil. At this stage it is called a crozier or fiddlehead. As the lower parts of  the frond expand and toughen up, they begin to photosynthesize, supporting the further growth and expansion of the frond. In case of many fronds, long hairs or scales provide additional protection to the growing tips before they are fully uncoiled. Circinate vernation may also be observed in the extension of leaflets, in the compound leaves of Cycads.

Rapid rotational movement of cytoplasm is due to increase in water content. Cytoplasmic streaming also called as protoplasmic streaming, the movement of the fluid substance within a plant or animal cell. The motion transports nutrients, proteins and organelles within cells. First discovered in the 1830s, the presence of cytoplasmic streaming helped convince biologists that cells were fundamental units of life.

A response of a plant, that causes movement independent of the direction of the stimulus is a nastic response. It is not a growth response, is reversible, and can be repeated many times. 

Scotopic in general means under low light conditions or night. For example scotopic stomata are stomata open during night and closed during day as against phototropic stomata, which are open during day but closed during night.