Plant Growth and Development

A set of vocabulary flashcards covering plant growth factors, hormones, types of plant movements, dormancy, photoperiodism, and vernalisation based on the lecture notes.

Growth

An irreversible activity that occurs in a living cell resulting in an increase in its overall size or the size of its parts.

Phytohormones

Organic molecules produced in small amounts in one or several parts of a plant and transported to target sites to regulate growth and development.

Auxins

Hormones derived from the Greek word auxein (to grow) that are responsible for cell elongation, vascular tissue differentiation, and apical dominance.

IAA

The only naturally occurring auxin that shows physiological activity.

Apical dominance

The inhibition of lateral bud formation triggered by auxins produced in the apical meristem.

Cytokinins

Hormones that stimulate cell division by promoting cytokinesis and lateral bud development.

Zeatin (Z)

The most active naturally occurring cytokinin, isolated from kernels of corn.

Gibberellins

A class of hormones produced in the shoot apex and seeds that promotes stem elongation, seed germination by breaking dormancy, and flowering.

Ethylene

A gaseous hormone found in ripening fruits and stem nodes that promotes fruit ripening and leaf abscission.

Ethaphon

A commercial substance used to induce fruit ripening.

Abscissic acid (ABA)

A natural hormone that acts as a growth inhibitor, promoting fruit and leaf abscission and maintaining seed dormancy.

Plant Movements

The capacity of plants to change their position in response to external environmental or internal stimuli.

Movement of Locomotion

Physical movement from one place to another, involving the whole plant body, an organ, or material within a cell.

Cyclosis

The movement of cytoplasm within a cell, also known as protoplasmic streaming.

Phototactic movements (Phototaxis)

The locomotion of a free-living organism towards or away from light.

Movement of Curvature

A bend or curvature seen in fixed plants as they change position to carry on functions effectively.

Xerochasy

A mechanical movement occurring due to the loss of water, such as the bursting of fern sporangia.

Hydrochasy

A mechanical movement occurring due to the absorption of water, such as the coiling of Equisetum elaters.

Nutation

A nodding growth movement in two directions exhibited by the stem apex of twiners like peas or beans.

Circumnutation

The spiral coiling of stems and tendrils resulting from the region of greater growth passing gradually around the growing point.

Epinasty

A non-directional movement caused by rapid growth on the upper surface (abaxial side) of an organ, occurring during the opening of leaves.

Hyponasty

A non-directional movement caused by greater growth on the lower side (adaxial side), such as closed sepals in a floral bud.

Tropic Movements

Directional growth movements of curvature where the response occurs either towards or away from an external stimulus.

Phototropism

A growth movement where a plant organ, such as the stem, curves due to a unilateral light stimulus.

Geotropism (Gravitropism)

Growth movements induced by the stimulus of gravity.

Hydrotropism

Growth movements in response to an external stimulus of water; roots are typically positively hydrotropic.

Thigmotropism (Haptatropism)

Plant movements that occur due to contact with a foreign body, most conspicuous in tendrils coiling around a support.

Nastic Movements

Non-directional movements of variation or turgor that are determined by the properties of irritable cells rather than the direction of the stimulus.

Nyctinastic movements

Diurnal 'sleeping' movements of leaves and flowers that respond to changes in day and night.

Seismonastic movements

Movements brought about in response to the external stimulus of shock or touch, notably seen in Mimosa pudica.

Dormancy

A temporary period of rest or inactivity when metabolic processes are at a minimum, primarily maintained by respiration.

Scarification

The physical destruction or scratching of a hard testa to make a seed permeable to water and oxygen to break dormancy.

Photoperiodism

The response of plants and animals to the length of the day and night.

Long Day Plants (LDP)

Plants that require more exposure to light for flowering, such as radish and spinach.

Short Day Plants (SDP)

Plants that require less exposure to light for flowering, such as rice and soybeans.

Day Neutral Plants (DNP)

Plants that flower based on a developmental stage regardless of day length, such as tomatoes and cucumber.

Vernalisation

The induction of flowering through exposure to cold temperatures, typically between $0\,^{\circ}C$ and $10\,^{\circ}C$.