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
Total eclipse of 1999. The chromosphere (literally, sphere of color) is the second of the three main layers in the Sun 's atmosphere and is roughly 2,000 kilometers deep. It sits just above the photosphere and just below the solar transition region. The density of the chromosphere is very low, it being only 10 â4 times that of the photosphere, the layer just below it, and 10 â8 times that of the atmosphere of Earth. This makes the chromosphere normally invisible and it can be seen only during a total eclipse, where its reddish color is revealed.