Fruits - Indehiscent • Dry Fruits That Do Not Split at Maturity (Indehiscent) Achene Nut Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Grain Samara Schizocarp Fruits - Indehiscent • Achene- a single-seeded fruit in which the seed is attached to the pericarp only at its base • The pericarp, the husk, is easily separated from the seed. • Ex. Sunflower, dandelion Fruits - Indehiscent • Nut- achene variation- one seeded, dry fruit with a hard, thick pericarp; develops with a cup or cluster of bracts at base • Ex- acorn, chestnut, hazelnut Fruits - Indehiscent • Grain (caryopsis)- a dry fruit in which the pericarp is tightly fused to the seed • Ex- corn, rice, wheat Fruits - Indehiscent • Samara- a dry fruit whose pericarp extends around the seed in the form of a wing • Ex. Maple, ash Fruits - Indehiscent • Schizocarp- a twin fruit that separates at maturity into two one-seeded fruitlets • Ex- parsley, carrot, dill Fruits • Aggregate Fruits- derived from a single flower with several to many pistils • Individual pistils mature as a clustered unit on a single receptacle • Ex- raspberries, strawberries Fruit • Multiple Fruit- derived from several to many individual flowers in a single inflorescence • Ex. Pineapple, fig, Osage orange, mulberries Fruit and Seed Dispersal • Wind Dispersal Small and Lightweight seeds. May have attachments like wings or hairs to help give them lift. Example- maple, ash, dandelion • Animal Dispersal Seeds can pass through an animal’s digestive tract. Some fruits and seeds have spines or thorns that catch in fur or feathers. Oils attract ants. Fruit and Seed Dispersal • Water Dispersal Some fruits contain trapped air. Some have a waxy coating. Both means help the seed to float. Example- coconut • Mechanical Ejection of Seeds Capsules dry and split in a way that flings the seeds far from the parent plant. Example witch hazel How Seeds Form • Pollination is the transfer of pollen from an anther to a stigma. • This may occur by wind or pollinating insects, birds or other animals. • Wind pollinated flowers usually lack showy floral parts and nectar since they don’t need to attract a pollinator. • Their non-showy flowers, however, do produce a lot of pollen to increase the likelihood that a pollen grain will land on a receptive stigma. Corn- pollinated by wind How Seeds Form • Brightly colored flowers, those with distinct markings or patterns on petals, containing fragrance or nectar, are most likely pollinated by insects, birds, or other animals. Birds, Butterflies, and Bats How Seeds Form • The surface of the stigma contains a chemical which activates the pollen, causing it to grow a long tube down the inside of the style to the ovules inside the ovary. • Fertilization is the union of the male sperm nucleus from the pollen grain and the female egg found in the ovary. • If fertilization is successful, the ovule will develop into a seed. How Seeds Form • Self-pollinating plants are capable of fertilizing themselves. That is, pollen from a single plant unites with an egg on the same plant. • In some plants, self-pollination may take place before the flower even opens. • In others, complex floral structure decrease the probability that pollen from another plant will reach the ovule. How Seeds Form • Cross-pollination occurs when pollen from one plant fertilized the ovule of a genetically different plant. • The surface of the stigma of self- incompatible plants recognized its own pollen and prevents it from germination, or causes the pollen to grow so slowly that it is not likely to reach the ovule before another pollen grain fertilized the ovule. How Seeds Form • Many fruit trees require cross-pollination for fruit development. How Seeds Form • Structure Cotyledons - Food storage organs that function as first seed leaves. Plumule - Embryo shoot. Epicotyl - Stem above cotyledon. Hypocotyl - Stem below attachment point. Radicle - Stem tip developing into a root. Germination • Germination is the beginning or resumption of seed growth. Seed must be viable. Some require period of dormancy. Scarification - After Ripening Favorable Environmental Factors - Imbibe water Germination of Dicot Seeds- ex. bean • 1. The radicle begins to grow and emerges from the seed to form the first root, called the primary root. • 2. The hypocotyl elongates, pushing its way out of the seed and above the soil. • 3. Below the soil, secondary roots begin to branch off of the primary root. • 4. When the hypocotyl emerges into the light, it straightens out and the epicotyl becomes visible, revealing a pair of true leaves and the apical meristem of the plant. • 5. The leaves expand and begin to do photosynthesis. Germination of Monocot Seed- ex. corn • 1. The radicle grows first, piercing the kernel and growing downward into the soil to form the primary root. • 2. The primary leaf of the shoot grows upward, pushing its way out of the kernel and the soil. • 3. Once the primary leaf reaches the light, it pushes through the coleoptile and begins to expand. • 4. Under the soil, lateral roots begin to develop from the primary root. • 5. In corn and other monocots, adventitious roots called prop roots also develop from the stem and push their way into the soil. How Seeds Grow • Viability of most seeds is significantly extended when the seeds are stored under conditions of low temperatures and kept dry. A few species produce seeds with no period of dormancy. - Vivipary How Seeds Grow • Viviparous plants produce seeds that germinate before they detach from the parent. • In many mangroves, the seedling germinates and grows under its own energy while still attached to its parent. • Some drop into the water and are dispersed by currents, but others develop a heavy straight taproot that commonly penetrates mud when the seedling drops, thereby effectively planting the seedling. How Seeds Grow Poa alpina, a grass which shows vivipary: the seeds germinate while still Red mangrove seeds germinate attached to the mother plant. while still on the parent tree. .