Control Systems In Plants


Control Systems In Plants

Plant Hormones

Five known classes of hormones control plant growth and development

Auxin – promotes fruit growth

Cytokinins – stimulate cell division

Gibberellins – stimulate growth in leaves and stems

Abscisic Acid – slows plant growth

Ethylene – inhibits root growth


Phototropism –bends shoot towards light; enhances photosynthesis

Gravitropism – uses specialized plastids


Roots display positive gravitropism

(grows down towards the earth) and the shoot displays negative gravitropism

(grows up out of the earth)



Developmental response to mechanical stimulation

Example: thicker stemmed plants are found in locations where the winds are strong

Turgor Movements

Turgor movements are relatively rapid, reversible plant responses

Biological Clocks

Biological clocks control circadian rhythms in plants and other eukaryotes


Photoperiodism synchronizes many plant responses to changes of season


Phytochrome functions as a photoreceptor in many plant responses to light and photoperiod

Control Systems

Control systems enable plants to cope with environmental stress


The study of plants began when early humans began to distinguish edible plants from poisonous ones.

Then began to make things from wood and other plant products.

Modern Science

Today scientists aim for increasing crop productivity, but the fun of discovery is what motivates most plant scientists.


Plant biology, one of the oldest branches of science, is driven by curiosity and need – curiosity about how plants work and a need to feed, clothe, and house an increasing human population. Plant biology is in the midst of a renaissance, in which new methods, coupled with clever choices of experimental organisms, have catalyzed a research explosion.