Selective absorption and reflection

An lilt- COI OKs of vegetation around us arise from the selective absorption and reflection of visible light. If our eyes were sensitive to ultraviolet radiation—the electromagnetic radiation at shorter wavelengths (higher frequencies) than violet light—wc would see an even richer tapestry of color, for substances also absorb... 

Chromophores are those groups within an organic structure that are essential to selective absorption and reflection of specific wavelengths of visible light. They are necessary for the appearance of a color other than white. Chromophore groups are represented by ... 

The lipoprotein membranes of the cell act as diffusion barriers they have a high resistance to passive penetration by ions. How then can we explain the rapid active movement of ions across such membranes One explanation is to postulate that the ions undergo reversible binding with some constituent of the membrane (this constituent is usually called the carrier). The ion is then visualised to pass across the thickness of the membrane, not as a free ion but as an ion-carrier complex (Fig. 7.3). This concept has the immediate attraction that it suggests an explanation of selectivity selective absorption would reflect the abundance in the membrane and chemical affinities of the carrier molecules. Ions which compete with one another would be ions capable of combination with the same carrier but the affinities of the carrier for the separate ions of the group... 

Figure 12.7.1 The phenomena of light reflection, absorption, and interference to create the appearance of color. Color arises as certain wavelengths of reflected light are selectively reinforced through constructive interference, while other wavelengths of light are canceled through destructive interference.

The particular colour which we see from objects coloured with dyes and pigments arises from the absorption and selective reflection and transmission of light from the materials containing the colorants into our eyes, there to be received by the photoreceptors and interpreted by the brain. 

The demonstration that eclectic mechanisms have been evolved by insects for coping with the potentially toxic concomitants of their ingested nutrients necessitates careful analyses of the processing of each of these compounds by each adapted herbivore. Furthermore, it is important to realize that in Itself, sequestration is nothing more than an end product of a series of reactions that may reflect selective absorption, metabolism of specific compounds, and excretion of selected allelochemics ). In the present review, these diverse processing strategies will be explored in order to illustrate the various ways in which a multitude of herbivores accommodate potential plant toxins. IVo lepidopterous species will be used as models which, hopefully, will emphasize both the elegance and complexity identified with insects as processors of plant-derived compounds. 

---