Lettuce. Lettuce is a fairly hardy, cool-weather vegetable that thrives when the average daily temperature is between 60 and 70Â°F. It should be planted in early spring or late summer. At high temperatures, growth is stunted, the leaves may be bitter and the seedstalk forms and elongates rapidly.ipburn is a physiological condition that causes lettuce to die back at the edges of the leaves. It results from a change in the moisture relationship between the soil and the plant. Clip off any brown leaf tissue and use the remainder of the leaf.
chromosphere. A layer of gas that lies above the photosphere of a star, such as the Sun. Thesaurus Antonyms Related Words Synonyms Legend: Switch to new thesaurus . Noun: 1. chromosphere - a gaseous layer of the sun's atmosphere (extending from the photosphere to the corona) that is visible during a total eclipse of the sun layer - a relatively thin sheetlike expanse or region lying over or under another
A star is a hot dense ball of gas so we should expect it have a continuous spectrum. But stars also have thin, transparent outer layers that light has to pass through. These layers produce absorption lines. Thus the light from the sun and stars are examples of absorption spectra.The stars' spectra differ from each other depending on temperature and composition. When astronomers first observed these differences in the 19 th century they devised a classification system that assigned letters to various spectral types.he lines occur where atoms of the gas have absorbed specific wavelengths of light. Hence we call this type of spectrum an absorption spectrum. If we view this transparent gas against a black background we would see that it also emits light (if it has an enough energy), giving an emission spectrum.