Two isogenic lines of tobacco, Nicotiana tabacum L., were used in an investigation of the effect of light quality on leaf shape and chlorophyll content. The plants received eight-hour days in a controlled environment chamber. At the end of each day, for six consecutive weeks, plants were exposed to red or far-red radiation to set phytochrome in the biologically active or inactive form, respectively. Plants that received red light last, each day, developed short broad leaves with a relatively high chlorophyll content, in contrast to the long, narrow, light green leaves formed on plants that received far-red light at the end of each day. Some potential problems relative to use of plant growth chambers were discussed.

(Full article published with kind permission from "Tobacco International")