20-foot screened enclosures. Each held about 600 sunflower plants. For one type of sunflower, seed size and total seed weight per flower head were about the same, regardless of which bees did the pollinating. For the second kind of sunflower, pollination by the sunflower leafcutting bee produced about a 30-percent increase in seed size and total seed weight per flower. Results of a follow-up test should be ready later this year or in early 2000.
Plants use phytochromes to sense sunlight.
Phytochrome-sensitive genes may trigger many responses such as flowering or making sugar for energy from sunlight, air and water. Phytochrome B doesn't bind if it is kept in the dark, according to the researchers' lab tests. The phytochrome investigations may eventually lead to new ways to change when and how plants respond to sunlight. This could speed development of genetically engineered plants that, for example, germinate or flower at times controlled by growers. New clues about how phytochrome B interacts with PIF3 to control genes should serve as a helpful new model of how other signaling pathways might work, such as those that control genes for resistance to drought or insects.