Base your answers to questions 69 and 70 on the information below and on your knowledge of biology.
scientists reprogram plants for drought tolerance
source: lancaster farming 2/21/15/aaas
arabidopsis plants respond to drought conditions by producing a stress hormone called aba. this hormone slows down plant growth and leads to a decrease in the plant’s use of water.
aba binds to specific receptors in the plant that cause the guard cells on the leaf surfaces to close the stomatal openings through which water vapor can normally pass. this reduces water loss during the drought conditions.
although it has been suggested that spraying plants with aba during a drought could be beneficial, it is not practical. the chemical is expensive to produce and quickly loses its ability to bind to cell receptors in the plant cells.
recently, however, scientists have found a way to modify the aba receptors in arabidopsis plants so they can be activated by another chemical that is both stable and inexpensive.
69 describe how the shape of molecules, such as the hormone aba, is critical to their function in the arabidopsis plant. [1]
70 explain how the response of the guard cells to a drought is part of a feedback mechanism. [1]