[14] Preparation of Extracts from Plants

This chapter describes some particular pitfalls of working with plant materials, along with solutions to these problems. It describes the protocols for the preparation of active cytoplasmic and chloroplastic extracts from a variety of plant tissues. Plant cells resemble bacterial cells more than animal cells in that they possess a rigid cell wall. Like animal tissues, however, many plant tissues are fibrous and difficult to macerate. The more fibrous material can be homogenized by freezing and grinding to a dry powder prior to addition of extraction buffer. When intact organelles must be isolated, however, there is a clear trade-off between yield and intactness. Plant cells contain, apart from the cytoplasm, four organelles from which enzymes might be purified. These are the nucleus, plastid, mitochondrion, and vacuole. For preparation of cytoplasmic, nuclear, or mitochondrial activities, a tissue devoid of chloroplasts is desirable. Commonly used are roots from dark-sprouted peas, soy or other beans, wheat, or maize.