Fruit develops from the ovary wall (pericarp) or accessory tissue, surrounds and protects the seeds, and aids in seed dispersal. Seed dispersal syndromes: characteristics of the fruit
ex. anemochory FRUIT
Most people think of fruit as something fresh from the market, or canned or frozen, to which you may want to add sugar before eating. However, fruit can be so much more. The key to understanding the diversity of fruit types is to know that there are many different strategies for seed dispersal.
Fruits follow flowers in the life cycle of a flowering plant. They are part of the sporophyte and are diploid. A fruit develops from the ovary of a flower after pollination and ovule development have occurred. Fruit functions, not only to surround and protect the developing seeds, but more importantly, to accomplish dispersal. There are many strategies of seed dispersal, including being carried by wind, water, or animals or even being eaten by animals. Words used to describe seed dispersal usually end in –chory and include anemochory for wind dispersal and epizoochory for being carried on the outside of an animal as well endozoochory for being carried in the gut of an animal.
Try to guess the mode or strategy of seed dispersal for the following fruits. cocklebur maple coconut Blueberries are an example of a simple fruit. One fruit develops from the ovary of each flower.
A first step in categorizng fruit types is to decide whether the fruit is simple (derived from one carpel or the fused carpels of a single ovary of a single flower), aggregate (derived from several separate carpels of a single flower), or multiple (derived from the ovaries of several flowers).
Pineapple A multiple fruit
Fruits can also be categorized as accessory or not. True fruit (pericarp) develops from the wall of the ovary and any other tissue involved is considered accessory. Strawberries are accessory fruits because the flesh edible part develops from the receptacle portion of the stem of the flower rather than the ovary wall. It is also an aggregate fruit!
Strawberry (not a true berry) Accessory fruit FLESHY FRUITS Berries are simple fruits in which all 3 layers (exocarp, mesocarp, and endocarp) of the pericarp are soft or fleshy, as in grapes and tomatoes. Seeds of berries can usually resist digestion and can be transported in the gut of an animal. See the next two slides for different types of berries. A pepo, like the watermelon or any other squash, is a berry with a hard exocarp. A hesperidium, as in the citrus fruits, is a berry with a leathery exocarp. Drupes, as in peaches and plums, are fruits with a stony and inedible endocarp. Whereas an animal may eat a berry and transport seeds in their gut, drupe seeds are protected by the inedible pit and are usually discarded and left behind after the rest of the fruit is eaten. Coconut is an interesting kind of drupe with a fibrous mesocarp for water dispersal and an endosperm within the seed that comes in both a solid and a liquid form. Most of us never see coconuts until after the fibrous exocarp and mesocarp (husk) have been removed. A pome is a kind of fleshy fruit in which the pericarp (from the ovary wall) forms a papery core that surrounds the seeds. The fleshy, edible portion of the fruit develops from specialized stem tissue, called the hypanthium (of a perigynous flower). Pomes, by definition, are accessory fruits! DRY FRUITS
All of the above fruits are classified as fleshy. Other fruits are dry at maturity. A caryopsis, like corn and other grains, is a simple, dry, and single-seeded fruit in which the pericarp is tightly fused to the seed coat. A corn kernel is not jut a seed, but an entire fruit.
caryopsis drupe DRY INDEHISCENT FRUITS
Other dry fruits that are also indehiscent (do not split open to release seeds at maturity) include the wind dispersed samara, the single-seeded achene with the seed attached at a single point inside the fruit (shell of a sunflower seed), and a nut with its single, unattached seed.
samara achenenut nut DRY DEHISCENT FRUITS
Some dry fruits split open to release seeds at maturity and are therefore termed dehiscent. These include the legume that splits on two sides (like a peanut), the capsule (like okra) that splits in several places - one split per carpel, and the follicle that splits on one side only.
legume capsule follicle Categories of simple vs. aggregate vs. multiple can be combined with other categories of fruit type. The so-called “cones” of sweetgum and magnolia are actually aggregate follicles. Strawberries are aggregates of achenes with accessory tissue! Here is an outline of all the fruit types you are responsible for:
I. Simple vs. aggregate vs. multiple
II. Non-accessory vs. accessory
III. A. Fleshy 1. berry a. pepo b. hesperidium 2. drupe 3. pome B. Dry 1. indehiscent a. caryopsis b. samara c. achene d. nut 2. dehiscent a. legume b. capsule c. follicle The life story of an angiosperm
Sporic meiosis Dominant sporophyte Heterospory Flowers and fruits Double fertilization . . . Flower development Pollination Fruit and seed development Ripening Seed dispersal After-ripening Germination Seedling growth and development Primary vs secondary growth . . . Flower development Etc. Within an anther…
Microspores to microgametophytes
tube cell and generative cell WithinAndroecium an anther…
Microspores producedMicrospores by meiosis to Microspores to microgametophytes by mitosis microgametophytes
Tube cell and Generative cell
Pollinationtube cell Pollenand tube extension Spermgenerative by mitosis cell Double fertilization WithinAndroecium an anther…
Microspores producedMicrospores by meiosis to Microspores to microgametophytes by mitosis microgametophytes
Tube cell and Generative cell
Pollinationtube cell Pollenand tube extension Spermgenerative by mitosis cell Double fertilization one with egg, one with central cell Within an ovary….. megaspore to megagametophyte
central cell with GynoeciumWithin – carpels,an ovary….. ovaries, ovules Megasporesmegaspore by meiosis to Megagametophytes by mitosis megagametophyte= 7 cells, 8 nuclei
zygote, within triploid endosperm, within seed coat (integuments) pollination followed by fertilization (double)
Parts of a seed: embryo (zygote) endosperm (fertilized central cell) seed coat (integuments) Stages of embryo development: globular heart-shaped – protoderm, ground tissue meristem, procambium torpedo
Parts of an embryo: cotyledons epicotyl hypocotyl radicle Parts of an embryo: cotyledons – seed leaves epicotyl – embryonic shoot apex, meristem hypocotyl – embryonic stem radicle – embryonic roo tip, meristem Parts of an embryo: cotyledons – seed leaves epicotyl – embryonic shoot apex, meristem hypocotyl – embryonic stem radicle – embryonic roo tip, meristem Types of seeds: albuminous exalbuminous
Exalbuminous – endosperm absorbed by cotyledons Albuminous – endosperm surrounds embryo Ripening
After-ripening scarification fire dormancy etc. Types of germination: 1. epigeous (epigeal) seed germination
Cotyledons rise above the earth. Cotyledons remain below ground. 2. Hypogeous (hypogeal) germination
corn oak