Practical 11

Study of fruit

Objectives: To study different types of fruits.

Requirements: Dissecting microscopes and magnifying lens.

Plant material:

Fruits of Mirabilis, Maize, Sunflower, Walnut, Pea, Calotropis, capsule of Cotton, Mango, Coconut, Tomato, Lemon, Cucumber, Apple, Clematis or Strawberry, Custard Apple, Michelia, Jackfruit and Ficus.

Seeds of Castor, Maize, Pea

Definition - A fruit results from maturation and fertilization of one or more flowers, and the gynoecium of the flower(s) forms all or part of the fruit.

On this basis of involvement of flower (s), inflorescence, ovule (s) fruits are classified into three main groups as -

A. Simple fruits

B. Aggregate fruits / Etaerio

C. Composite or multiple fruits

A. Simple fruits

Simple fruits can be either dry or fleshy, and result from the ripening of a simple or compound ovary in a flower with only one carpel. Dry fruits may be either dehiscent (opening to discharge seeds), or indehiscent (not opening to discharge seeds)

I. Simple, Dry, Indehiscent fruits

  1. Achene: The fruit develops from polycarpellary syncarpous unilocular ovary. Pericarp and testa are very close to each other surrounding a single seed but are separable. e.g. Mirabilis, Amaranthus.
  2. Caryopsis: The fruit develops from bicarpellary, syncarpous, superior, unilocular ovary. Pericarp and testa are fused to form hull. e.g. Corn, wheat.
  3. Cypsela: The fruit develops from inferior, bicarpellary, syncarpous, unilocular ovary. Pericarp and testa are separable. e.g. Sunflower.
  4. Nut: The fruit develops from polycarpellary, syncarpous, ovary. It has thick, hard, woody pericarp, which is free from testa. e.g. Walnut, Oaknut.

II. Simple, Dry, Dehiscent fruits

  1. Legume: This fruit develops from superior monocarpellary ovary. It opens on both the sutures, dorsal and ventral and produces two valves. e.g. Beans, pea, groundnut.
  2. Follicle: The fruit develops from polycarpellary, partially syncarpous gynaecium. Ovaries are free each developing into a follicle that opens along one suture only forming one valve. e.g. Vinca, Nerium, Calotropis.
  3. Capsule: The fruit develops from polycarpellary, syncarpous superior or inferior gynaecium. Fruit opens by several splits or pores forming many valves. e.g. Cotton, poppy, Lady’s finger.

III. Simple Fleshy fruits: Pericarp is succulent, juicy at maturity, hence indehiscent.

a) Drupe: 1- to 2-seeded; pericarp is differentiated into three layers with stony endocarp, hence called stone fruit. It has two types as -

i. Fleshy drupe: It develops from polycarpellary, syncarpous, superior ovary. Outer layer of the fruit is epicarp, middle edible, fleshy is mesocarp, and endocarp is hard and stony. e.g. Mango.

ii. Fibrous drupe: It develops from tricarpellary, syncarpous, superior ovary. Epicarp is leathery; mesocarp is fibrous; endocarp is hard and stony. Edible part is solid and liquid endosperm. e.g. Coconut.

b) Berry: The fruit develops from polycarpellary, syncarpous, superior or inferior, multilocular gynaecium. It is one to many-seeded, pericarp is undifferentiated, and placenta forms flesh of the fruit in which seeds are embedded. e.g. Brinjal, Tomato, Guava.

c) Hesperidium: Special type of berry develops from polycarpellary, syncarpous, superior or inferior, multilocular gynaecium. Here pericarp is differentiated into three layers –Outer Epicarp – called as rind, Middle mesocarp – fibrous, inner endocarp develops into juicy, hair like sacs. e.g. Lemon, Orange.

d) Pepo: This fruit develops from inferior, tricarpellary, unilocular ovary. Pericarp undifferentiated, tough, Placenta forms bulk of flesh. e.g. Cucumber, Gourds.

e) Pome: This berry develops from polycarpellary, apocarpous, superior; gynaecium. Thalamus grows and surrounds the achenes after fertilization. It forms edible portion; hence pseudocarpic fruit. e.g. Apple, peach.

B. Aggregate fruits

These fruits develop from single flowers that have multiple carpels (style + stigma + ovary) which are not joined together, i.e. each pistil contains one carpel.

i. Etaerio of achenes: Each achene possesses persistent hairy style that helps is dispersal of fruit. e.g. Clematis, Strawberry.

ii. Etaerio of follicles: Individual fruitlet is of follicle type. All the follicles are attached to thalamus. They dehisce by dorsal suture. e.g. Michelia, Sterculia.

iii. Etaerio of berries: Numerous free carpels are placed on conical thalamus that develops into one seeded berries and compact mass. e.g. Custard apple.

3. Composite or multiple fruits:

Formed by fusion of several separate pistils of several grouped flowers/ inflorescence. Peduncle with accessory parts is involved in formation of fruit. Hence, they are pseudocarpic fruits.

i. Syconus: Hypanthodium inflorescence axis is in the form of thick, fleshy, cup shaped receptacle. Many achenes are present inside it. Receptacle is edible. e.g. Ficus.

ii. Sorosis: In pineapple, the peduncle of the spike, fertile bracts and perianth all become thick and fleshy at maturity. Individual fruit is of achene type. e.g. Ananas sativus. In jackfruit, many sterile, elongated, spiny bracts in the spadix are present which produce spiny rind of the fruit. Perianths of the individual flowers are thick and fleshy which are edible. e.g. Artocarpus.