Seed dispersal is necessary for plant propagation and survival. Seeds can be dispersed either by the plant itself through explosive mechanisms, or by external agencies like wind, water, and animals. Some plants have adapted wings, hairs or hooks to aid dispersal by wind or animal transport, while others produce light, buoyant fruits that can spread via water. Common methods of dispersal include explosive seed pods that fling seeds distances, floating seeds carried by water, or berries eaten and dispersed through animal feces.

1. SEED DISPERSAL

2. NEED FOR DISPERSAL To spread out and grow in new places. To get sufficient space, light, and nutrients for propagation. Evolution of species.

3. HOW IT WORKS? Seeds lacks power of locomotion so are dependant on external agencies for dispersal.

4. AGENCIES INVOLVED:- Two broad categories are:- BY PLANT ITSELF BY EXTERNAL AGENCIES

5. BY PLANT ITSELF {autochory} Plants disperse their seeds on their own. They disperse seeds by bursting with a sudden jerk. Loud sounds can be produced too during their dehiscence. The process may also be termed as “EXPLOSIVE MECHANISM”

6. MAIN EXAMPLES OF AUTOCHORY:- DRY PODS OF FAMILY LEGUMINOSEAE (PEA, BEAN) FIRST BREAKS INTO TWO HALVES.

7. THEN THESE HALVES TWIST SPIRALLY TO THROW SEEDS TO LONG DISTANCES THE TWO HALVES CURLS BACK ND FLICK OUT THE SEEDS IN AN EXPLOSIVE MANNER. (COMPARE THE CURLED POD WITH THE ENTIRE ONE)

8. EXAMPLE 2nd GORSE IS A GOOD EXAMPLE. IN SUMMERS THE EXPLODING PODS SOUNDS ALMOST LIKE GUN SHOTS. SMALL SEEDS ARE THROWN VERY EFFECTIVELY FROM IMMEDIATE AREA.

9. THE EXTERNAL AGENCIES ANEMOCHORY (BY AIR) HYDROCHORY (BY WATER) ZOOCHORY (BY ANIMALS)

10. ANEMOCHORY:- MAIN CHARACTERISTICS :- SEEDS ARE DISPERSED BY THE AGENCY OF WIND. SEEDS MUST BE LIGHT ND SMALL. THEY MAY ADOPT DIFFERENT ADAPTATIONS LIKE OUTGROWTHS, HAIRS, WINGS etc… WHICH INCREASE THEIR SURFACE AREA TO FLY IN WIND FOR LONGER.

11. MAIN EXAMPLES :- “ PEPPER POT TYPE” The flower ovary contains the seeds .It becomes dry and disperses the seeds when shaken by wind

12. 2. “PARACHUTE TYPE ” FEATHERY HAIRS HELPS THEM TO FLOAT ON WIND FOR LONG TIME.

13. MORE TYPES MAY BE:- WINGED SEEDS COTTON GRASS

14. HYDROCHORY:- MAIN CHARACTERISTICS ARE:- PLANTS GROWING NEAR WATER DISPERSES SEEDS THROUGH WATER. SOME KIND OF FLOATING DEVICES ARE ALSO FORMED LIKE FIBROUS MESOCARP IN COCONUT, EMBEDDING OF SEEDS IN LONG THALAMUS IN CASE OF LOTUS OR SMALL, LIGHT AND AIR FILLED SEEDS IN LILLY etc….

15. 1. “POND IRIS” THE SEED POD BREAKS OPEN WHEN THEY RIPEN WITH A FORCE. BEING LOCATED NEAR WATER THOSE SEEDS THAT FALL IN WATER FLOWS AWAY THROUGH LONG DISTANCES.

16. ZOOCHORY:- MAIN CHARACTERISTICS ARE:- THE SEEDS ARE LIGHT AND ARE STICKY OR PROVIDED WITH HOOKS SOME PLANTS PRODUCE FLESHY EDIBLE FRUITS THAT ARE DISPERSED THROUGH THE WASTES EXCREATED BY THE ANIMALS. HUMAN TRAVELLERS ALSO CARRY SOME SEEDS WITH THEM.

17. 1. “BURDOCK SEED HEAD” AS SHOWN THESE SEEDS OF THE PLANTS HAVE HOOKS ON THEIR SURFACE. THESE ARE EDHERED TO FUR OF MAMMALS AND ARE SPREAD .

18. 2. “THE BERRIES” THE BERRIES ARE EATEN BY THE BIRDS SUCH AS BLACKBIRDS AND PIGEONS. MICE, DEER AND EVEN FOXES ALSO EAT THEM. THE SMALL HARD SEED IS HIDDEN INSIDE THE FRUIT THAT PASSES INTO THE GUT OF THE OF THE ANIMAL. THE SEED REMAINS UNDIGESTED AND IS EXCREATED OUT AS SUCH AND IS DISPERSED.

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