Seed germination is the process by which a seed emerges from dormancy to sprout and grow into a seedling. A seed contains an embryo plant and food reserves to fuel initial growth. The germination rate describes the percentage of seeds that will germinate under proper conditions, and is useful for crop planning. Seed germination is influenced by external factors like water, temperature, oxygen, and light as well as internal factors.

4. GERMINATION RATE:- IN AGRICULTURE AND GARDENING, THE GERMINATION RATE DESCRIBES HOW MANY SEEDS OF A PARTICULAR PLANT SPECIES, VARIETY OR SEED LOT ARE LIKELY TO GERMINATE. IT IS USUALLY EXPRESSED AS A PERCENTAGE, E.G., AN 85% GERMINATION RATE INDICATES THAT ABOUT 85 OUT OF 100 SEEDS WILL PROBABLY GERMINATE UNDER PROPER CONDITIONS. THE GERMINATION RATE IS USEFUL FOR CALCULATING THE SEED REQUIREMENTS FOR A GIVEN AREA OR DESIRED NUMBER OF PLANTS.

5. FACTOR AFFECTING OF SEED GERMINATION:- (A) EXTERNAL FACTOR (B) INTERNAL FACTOR

9. AFTER THE SEEDLING EMERGES FROM THE SEED COAT AND STARTS GROWING ROOTS AND LEAVES, THE SEEDLING'S FOOD RESERVES ARE TYPICALLY EXHAUSTED; AT THIS POINT PHOTOSYNTHESIS PROVIDES THE ENERGY NEEDED FOR CONTINUED GROWTH AND THE SEEDLING NOW REQUIRES A CONTINUOUS SUPPLY OF WATER, NUTRIENTS, AND LIGHT.

13. MANY SEEDS GERMINATE AT TEMPERATURES SLIGHTLY ABOVE ROOM-TEMPERATURE 60-75 0 F (16-24 C), WHILE OTHERS GERMINATE JUST ABOVE FREEZING AND OTHERS GERMINATE ONLY IN RESPONSE TO ALTERNATIONS IN TEMPERATURE BETWEEN WARM AND COOL. SOME SEEDS GERMINATE WHEN THE SOIL IS COOL 28-40 0 F (-2 - 4 0 C), AND SOME WHEN THE SOIL IS WARM 76-90 0 F (24-32 0 C). SOME SEEDS REQUIRE EXPOSURE TO COLD TEMPERATURES (VERNALIZATION) TO BREAK DORMANCY.

14. SEEDS IN A DORMANT STATE WILL NOT GERMINATE EVEN IF CONDITIONS ARE FAVORABLE. SEEDS THAT ARE DEPENDENT ON TEMPERATURE TO END DORMANCY HAVE A TYPE OF PHYSIOLOGICAL DORMANCY. FOR EXAMPLE, SEEDS REQUIRING THE COLD OF WINTER ARE INHIBITED FROM GERMINATING UNTIL THEY TAKE IN WATER IN THE FALL AND EXPERIENCE COOLER TEMPERATURES. FOUR DEGREES C IS COOL ENOUGH TO END DORMANCY FOR MOST COOL DORMANT SEEDS, BUT SOME GROUPS, ESPECIALLY WITHIN THE FAMILY RANUNCULACEAE AND OTHERS, NEED CONDITIONS COOLER THAN -5 0 C.