Download FRUITS A FRUIT IS A MATURE OVARY CONTAINING SEEDS. A

FRUITS
A FRUIT IS A MATURE OVARY CONTAINING
SEEDS. A VEGETABLE IS A PLANT PART NOT
INVOLVED IN SEXUAL REPRODUCTION:
LEAVES (LETTUCE, CABBAGE, CELERY), STEMS
(POTATOES), ROOTS (PARSNIPS, CARROTS) OR
FLOWER BUDS (BROCCOLI). THIS IS THE
BOTANICAL DEFINITION. LEGALLY, SOME
FRUITS ARE CALLED VEGETABLES
(TOMATOES, CUCUMBERS, STRING BEANS)
BECAUSE FRUITS ARE CONSIDERED TO BE
SWEET AND IN THE NATURE OF A DESSERT
FOOD WHILE VEGETABLES ARE SAVORY AND
ARE EITHER SALADS OR MAIN COURSE FOODS.
ALL FRUITS ARISE FROM FLOWERS (PISTILS)
AND SO ARE FOUND EXCLUSIVELY IN THE
1
ANGIOSPERMS. FERTILIZATION USUALLY
DETERMINES WHETHER OR NOT THE OVARY
(OVARIES) OF A FLOWER WILL DEVELOP INTO
A FRUIT. TYPICALLY IF AT LEAST A FEW OF
THE OVULES ARE FERTILIZED A FRUIT WILL
FORM; IF NO OVULES ARE FERTILIZED THE
FLOWER WITHERS AND DROPS OFF.
IN SOME CASES POLLEN GRAINS CONTAIN
HORMONES THAT MAY START FRUIT
DEVELOPMENT AND THIS MAY BE ENOUGH –
NO FERTILIZATION NEEDED. HOWEVER,
HORMONES PRODUCED BY THE DEVELOPING
OVULES PROMOTE THE GREATEST FRUIT
GROWTH – THESE HORMONES IN TURN
STIMULATE THE PRODUCTION OF MORE FRUIT
GROWTH HORMONES BY THE OVARY WALL.
2
FRUITS THAT DEVELOP FROM OVARIES
HAVING UNFERTILIZED EGGS ARE
PARTHENOCARPIC – THEY ARE SEEDLESS
(NAVEL ORANGES, BANANAS, SOME GRAPES &
FIGS). IN SOME PLANTS FERTILIZATION DOES
OCCUR BUT THE OVULES FAIL TO DEVELOP
(GREEN SEEDLESS GRAPES). PARTHENOCARPY
CAN BE INDUCED ARTIFICIALLY BY APPLYING
HORMONE SPRAYS TO FLOWERS (SEEDLESS
TOMATOES). SOME SEEDLESS FRUITS ARE THE
RESULT OF HYBRIDIZATION: BY CROSSING
TYPES WITH DIFFERENT CHROMOSOME
NUMBERS. THE FI GENERATION IS STERILE SO
FERTILIZATION & SEED FORMATION DOES NOT
OCCUR (SEEDLESS WATERMELONS).
3
THE OVARY WALL FORMS THE BULK OF THE
FRUIT USUALLY. THE SKIN FORMS THE
EXOCARP (OUTERMOST LAYER), THE
INNERMOST LAYER AROUND THE SEED IS THE
ENDOCARP, THE MESOCARP IS THE NAME
GIVEN TO THE LAYER BETWEEN THE EXOCARP
AND ENDOCARP. THE THREE REGIONS
COLLECTIVELY ARE CALLED THE PERICARP.
A GOOD EXAMPLE IS A PEACH, PLUM OR
CHERRY. THE SKIN IS THE EXOCARP, THE
FLESHY PART THAT FORMS THE BULK OF THE
FRUIT IS THE MESOCARP; THE HARD “PIT” IN
THE CENTER IS THE ENDOCARP. INSIDE THE
ENDOCARP IS THE SEED.
IN MANY CASES THESE LAYERS ARE
INDISTINGUISHABLE AND IN SOME CASES NOT
4
ALL ARE PRESENT. IN SOME FRUITS THE
PERICARP MAY BE QUITE THIN OR EVEN FUSED
TO THE SEED COAT. SOME FRUITS HAVE
ADJACENT FLOWER PARTS, SUCH AS THE
RECEPTACLE OR CALYX, FUSED TO THE
OVARY AND BECOME PART OF THE FRUIT.
KINDS OF FRUITS
THERE ARE MANY KINDS OF FRUITS, MOST
BASED ON THE TYPE OF MATURATION OF THE
OVARY WALL OR PERICARP.
FLESHY FRUITS ARE THOSE WHOSE MESOCARP
IS AT LEAST PARTLY FLESHY AT MATURITY
(PEACHES).
SIMPLE FLESHY FRUITS ARE THOSE DERIVED
FROM A FLOWER WITH A SINGLE PISTIL.
5
AN AGGREGATE FRUIT IS ONE THAT IS
DERIVED FROM A SINGLE FLOWER WITH
SEVERAL TO MANY PISTILS. EACH PISTIL
MATURES AS A CLUSTERED UNIT ON A SINGLE
RECEPTACLE (RASPBERRIES, STRAWBERRIES).
MULTIPLE FRUITS ARE DERIVED FROM
SEVERAL TO MANY FLOWERS IN A SINGLE
INFLORESCENCE. EACH FLOWER HAS ITS OWN
RECEPTACLE BUT AS THE FLOWERS DEVELOP
INTO FRUITS THEY UNITE OR FUSE TO FORM A
SINGLE LARGE “FRUIT” (PINEAPPLES, FIGS,
MULBERRIES).
DRY FRUITS ARE THOSE WHOSE MESOCARP IS
DRY AT MATURITY. THE PERICARP IS OFTEN
THIN AND NOT DISTINGUISHABLE INTO
6
LAYERS. DRY FRUITS ARE DIVIDED INTO TWO
GROUPS:
1. DEHISCENT FRUITS – THE FRUIT AT
MATURITY NATURALLY SPLITS OPEN TO
RELEASE THE SEEDS.
2. INDEHISCENT FRUITS – DO NO SPLIT OPEN AT
MATURITY TO RELEASE SEEDS. FLESHY
FRUITS ARE ALSO INDEHISCENT.
FRUIT FUNCTIONS
FRUITS HAVE TWO PRIMARY FUNCTIONS:
1. TO PROTECT THE YOUNG & DEVELOPING
OVULES AND SEEDS.
2. TO AID IN DISPERSAL OF THE SEEDS. FRUITS
USE WIND, WATER, AND VARIOUS ANIMALS
(INCLUDING HUMANS) TO DISPERSE THEIR
7
SEEDS AROUND THE WORLD. FRUITS MAY BE
EATEN BY ANIMALS, THE SEEDS PASS
THROUGH THE DIGESTIVE TRACT AND ARE
DEPOSITED IN FECES (FERTILIZER) SOME
DISTANCE FROM THE PARENT PLANT. FRUITS
MAY ALSO STICK TO THE FUR OR FEATHERS
OR CLOTHES OF AN ANIMAL AND FALL OFF
LATER. SOME FRUITS ACT AS A CATAPULT –
WHEN THEY DRY AND SPLIT OPEN THEY
CATAPULT THEIR SEEDS SOME DISTANCE.
FRUITS CAN FLOAT IN THE AIR ON
PARACHUTES OR FLOAT ON THE WATER LIKE
A BOAT. THE WAYS FRUITS DISPERSE SEEDS IS
EXTREMELY DIVERSE.
8