Plant Tropisms Research Paper Example | Topics and Well Written Essays - 750 words

Plant Tropisms - Research Paper Example Higher plants compensate for this deficiency through elaborate specialized chemical metabolic pathways. For instance plants exude toxins on their surface to ward off potential enemies; others alter their pigments in reaction to light intensity and others still, enhance their reproductive efficiency through chemo-attractants (Hart, 4). In all these cases plants sense an external stimulus and respond to it appropriately. The ability of plants to sense unfavorable conditions in their immediate environment and as a result alter their growth is referred to as tropism. Tropisms are directional movements in plants in response to directional stimulus. Tropic responses are brought about by differential growth on the part of the plant organs. Positive tropism occurs when the plant alter growth in the direction of the incoming stimulus. Negative tropism on the other hand, occurs where plant growth happens in the opposite direction to the incoming stimulus. Orthotropic response is where a stimulated organs aligns itself with the plane of the stimulus. These can be negatively or positivelyorthotropic. Seedlings wholly display one or the other of these two types of tropisms. Mature tissues however, vary greatly. Plagiotropic responses occur when an organ orients itself at an angle to the direction of incoming stimulus such as occur in branches and some roots. Orientation at right angles is termed diatropic ( Hart 23). Phototropism is the directional growth of an organ in response to blue light. It is under the control of blue light photo – receptors called phototropins (Hangarter, 2000, p. 25). Plants need light energy in order to carry out the process of photosynthesis. As such many aerial parts of the plant show some form of positive phototropism. These include leaves, branches, stems and most roots. Plant phototropism is not only restricted to blue light however, plant morphogenesis