Chapter 14 Flowers and Fruit

Chapter 14: Flowers and Fruit Flowering plants come in three basic types: 1. annuals grow in a single season or year and die after they flower. They only flower once. 2. biennials grow for two seasons, and flower and die the second year. They only flower once. 3. perennials grow for many years and can flower repeatedly. Flowers may be single, or grouped together to form an inflorescence. The main types of inflorescences are: catkins - hang down with flowers close together. Fig 8.3 umbels - have several flowers all attached to the same point in a semi-circle. Fig 8.7 spike - has flowers joined directly to a tall stem raceme - has flowers on stalks alternating up the stem corymb - has flowers that form a flat surface, yet are attached to different points of the stem. Flowering plants are either : 1. Short day ( long night ) plants : flower in winter/spring eg poinsettia, strawberry 2. Long day ( short night ) plants : flower in summer eg lettuce, tomato 3. Day neutral plants : flower any time of year eg peas, corn, rice Plants actually measure night length, not day length. A flash of bright light in the night will reset the plants internal clock. Night length is measured using a protein : phytochrome which has two forms : Pr ( absorbs red light ) and Pfr ( absorbs far red light ). After pollination, the seed develops inside a fruit. Fruit is made of three layers: the exocarp is the outer layer. The mesocarp forms the fleshy tissue in the middle and the endocarp surrounds the seed. Fig 8.8. Types of fruit Pome - most of the fruit is formed from the receptacle (under the flower) eg pear, apple Drupe - has fleshy fruit and a single seed with a hard endocarp eg peaches, coconut and olives Berry - has many seeds eg tomatoes, peppers and cucumber but not strawberries! Aggregate fruit - develop from one flower with many pistils eg strawberries. Legumes - split along two sides eg beans, peas Capsules - are dry fruit that have several carpels eg orchids Nuts - have one seed and a hard pericarp eg acorns Grains - have the fruit and seed joined closely together eg wheat, rice, barley. Multiple fruits - come from several different flowers joined together eg pineapples.