School of Sciences, Lautoka Campus BIO509 Botany Lecture 21: Angiosperms Photo courtesy of Prof. Randy Thaman

Flowers , Fruits and seeds

Learning Outcomes Know the parts of a flower and the function of each part. Understand the differences between monocot and dicotyledonous plants. Know the different types of fruits. Learn the adaptations of fruits and seeds that aid in dispersal.

Flowers Flowering plants are essential for animals and humanity. Provide countless products. 80% of world’s food resources. Flowering plant habitats are varied as their forms.

Flowering plant types Annuals – life cycle is completed in a single season, parent plant dies. Biennials – life cycle is completed in two growing seasons. Perennials – life cycle is completed over several growing seasons.

Two major classes Monocots Dicots More than ¼ of angiosperm species are monocots (~70,000 sp.) More than ⅔ of angiosperm species are eudicots (~170,000 sp.)

All flowers share the basic features

Inflorescences Groups of several to hundreds of flowers that may open at the same time

Seed and fruit formation After fertilization Seeds develop from the ovules. Fruits develop from the ovary.

Fruit Matured ovary and its accessory parts. However, it may have other bits fused to it (E.g. hypanthium, calyx, etc). Some form by apomixis (seed formation without sexual fusion).

What is the function of fruits?

Mature fruit had three major regions Ovary wall (known as pericarp in the fruit) often thickens and develops into 3 layers Exocarp – outer layer Mesocarp – middle layer Endocarp – inner layer

Classification is based on these features. Fruits may be fleshy or dry at maturity. May or may not split to expose the seeds. May be derived from a single ovary or from multiple ovaries. Classification is based on these features.

Different kinds of fruits

Fleshy fruits Mesocarp is partly fleshy at maturity. Simple fleshy fruits – formed from a flower with single carpel (ovary), superior or inferior ovary. Fruit types include: - Drupe - Berry - Pepo - Hesperidium - Pome

Drupe Simple fleshy fruit with one seed enclosed by a hard stony endocarp or pit. Usually superior ovary. Mesocarp not always obviously fleshy (e.g. coconut). E.g. cherry, peach, plum, olive, almond, coconut

Berries Thin-skinned simple fleshy fruit with mesocarp and endocarp difficult to distinguish from each other Derived from superior, compound ovary Most more than one seed Avocados and dates one-seeded E.g., grapes, peppers, egg-plant, tomato, papaya, guava.

Pepo Berry with a relative thick rind Restricted to members of the pumpkin family (Cucurbitaceae) E.g. squash, cucumber, pumpkin, gourd, watermelon, cantaloupe

Hesperidium Berry with a leathery skin containing oils. Restricted to and characteristic of the citrus family (Rutaceae).

Accessory fruit with thick hypanthium. Pomes Accessory fruit with thick hypanthium. Bulk of flesh comes from enlarged floral tube or receptacle that grows up around the ovary. E.g Apples and pears.

Compound Fleshy Fruits - derived from several ovaries or flowers. Fruit types include: Aggregate fruit Multiple fruit Synconium (multiple fruit)

Aggregate fruit Develop from a single flower with numerous pistils. Pistils mature as a clustered unit on a single receptacle E.g. Raspberries, Strawberries.

Multiple fruits Develop from many individual flowers in a single inflorescence. E.g. Pineapples, figs, maize, noni (kura), pineapple, breadfruit, mulberry.

Multiple fruits

Syconium A type of multiple fruit in which the receptacle entirely encloses the inflorescence. Characteristic of figs (genus Ficus). Pollinated by tiny wasps that enter the tiny opening at the top.

Individual flowers

1 2 Fig Pollination 3 4

Dry Fruits Fruits with a dry pericarp Dehiscent fruits Split open at maturity, seed fused to pericarp. Fruit types include: Follicles , Legumes, Siliques, Capsules.

Follicle Formed from single carpel & splits open down one side to release the seeds. Splits open along a seam. E.g., milkweed, magnolia, banksia, monk’s hood.

Legume (pod) Splits along two seams. Formed from single carpel with seeds in one row. Mostly in legumes (Fabaceae = Leguminosae). E.g. Peas, beans. Peanuts unusual: do not split on their own

Silique Splits along two seams, with seeds borne on a central partition. Originates from 2 carpels. Characteristic of mustard family (Brassicaceae). E.g., mustard, watercress, cabbage, raddish.

Capsule Formed from a compound ovary, splits open along multiple seams or forms pores. May open along seams, between seams, or by pores. E.g. poppy, cotton, orchids, lilies.

Indehiscent fruits Do not split open at maturity, seed fused to pericarp. Fruit types include: Achene Nut Caryopsis Samara Schizocarp

Achene only the base of seed is fused to pericarp. Seed is easily separated from ovary wall. All of Asteraceae, e.g. sunflower seeds The real fruits of the strawberry are also achene but are fleshy fruits.

Nut Like achene, but larger and pericarp harder & thicker. Single seed with hard pericarp/husk Develops with a cluster of bracts at base. Acorns, hazelnuts, hickory nuts, walnut.

Many fruits called nuts in English are not actually nuts. E.g., peanuts, coconut, Brazil nuts almonds, cashews

Caryopsis (grain) Indehiscent fruit with the pericarp tightly united with the seed and inseparable. One-seeded fruit/seed fused with seed coat (pericarp) All members of the grass family (Poaceae)

Samara Pericarp extends out to form a wing or membrane. One wing common, but sometimes more. Aids in dispersal. E.g., maple, ash

Schizocarp Comprises two or more segments (mericarps) that separate from each other. Split apart at maturity. Whole seed separates to form 2 separate 1-seeded fruitlets Apiaceae (carrot family) species: twin fruits (more in other families)

Questions??