Nov 10; Plant Communication and Behavior

Plant communication and behavior relies on phenotypic plasticity. Plants are unable to run away, they have to live with the consequences of their behaviors.

The various cues that a plant recieves can affect a number of things including, shoot phenotype and root development. How do plants respong to shading, shade from their own leaves and shade from others?

They either confront, avoid, or tolerate. When a plant confronts a competitor the plant will have an elongation response, and increase apical dominance. When a plant avoids a competitor the plant will grow away from the competitor or have dependent germination. When a plant tolerates a competitor it will just be tolerant to the shade morphologically and physiologically.

How do plants perceive light levels and wavelengths? They possess photoreceptors, phytochromes, crytochromes, phototropins, and some unidentified UVB sensitive to particular wavelengths.

Plants can tell the difference between being in the shade of a building or a rock, versus shade of another plant. This is because of the different wavelengths of light that are absorbed by other objects. Red light is absorbed by plant canopy, far-red isn’t. That means a plant with full sun is being exposed to different ratios of red and far-red wavelengths opposed to plants which are being shaded.

Shade avoidance is a collection of responses to vegetative shading. Plants can anticipate and respond to future shade. Plants elongate less when wearing a collar that filters out far-red light reflected from adjacent leaves. Another example of this is Portulaca oleracea, or common parsalin, grows and branches in a wa that minimizs self-shading. When lower red/far-red ratios occuring in one direction the plant grows away from it.

Shade tolerant species tend to be very slow growing. The differences in allocation cause long-lived shade-tolerant plants that invest relatively more resources into defense against herbivores and pathogens.

Ligh information is more than just quantity and spectrum. It is likely that plants respond to a richer range of light cues. Vertical, mid-day shade might indivate a very tall neighbor where the plant would not want to compete to grow larger. Horizontal and late-day low r:fr cues might indivate similarly sized neighbors where the plant would compete with its neighbor.

Somatic Competition happens when plants compete with themselves. There are many redundant organs that compete with each other. In “Somatice Competition” the plant can increase performance by putting more resources into more successful organs. The growth rate can vary. Experimental evidence supports the 3 types of responses; independant, cooperative, competitive.



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