Tag: seed dormancy

Stratification involves the treatment of seeds at low temperature (5-10 degree C) under sufficiently moist conditions to break its dormancy and to induce germination.

Dormancy is defined as the condition of seed when it fails to germinate even though the envoirnment condtions, usually considered favourable for active growth, are present.

A. Ethylene serves as a hormone in plants. It acts at trace levels throughout the life of the plant by stimulating or regulating the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves.

B. Cytokinins are plant hormones that cause increased celldivision by stimulating the process of mitosis. 

C. Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in terminal buds. This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season.

So, the correct answer is 'Abscisic acid'.

A. The storage function  of Lecythis and (Brazil nut) Bertholletia is neither endosperm nor cotyledon, but hypocotyl.

B. Nymphae- Food stored in perisperm.

C. Cotton- Food stored in cotyledons.

D. Rice- Food stored in endosperm.

So, the correct answer is 'Bertholettia'.

Germination Inhibitors: They occur in the seed coats and cotyledons of the embryos. The important germination inhibitors causing seed dormancy are abscisic acid, phenolic acid, ferulic acid, coumarin, short fatty acids and cyanogenic chemicals, e.g., Apple, Peach, Ash, Cucurbita, Iris, Xanthium. Counteracting Inhibitors: Inhibitors are destroyed by dipping seeds in KNO$ _3$, thiourea, ethylene chlorohydrin and gibberellin. IBA, GA, ethylene are counteracting inhibitors of seed dormancy while ferulic acid is a germination inhibitor. So, the correct answer is 'Ferulic acid'.

Gibberellins (GA) are well-known plant hormones that promote seed germination and are effective in breaking seed dormancy.

A. Scarification: Hard, impermeable seed coat is weakened or ruptured by filing, chip­ping, hot water 

B. Vernalisation- The cooling of seed during germination in order to accelerate flowering when it is planted.

C Impaction- It means to strike something with force. This method implies to the vigorous shaking of the seeds

D. Stratification: Seeds are moistened and exposed to oxygen for variable period at very low (chilling) or high temperature.

So, the correct answer is 'Stratification'.

Thiourea acts as a chemical agent that helps break seed dormancy by counteracting the effects of germination inhibitors present in the seed.

Quiescence is a condition in which seeds do not germinate due to unfavourable environmental conditions. When favrouable conditions return, the seed will germinate. Seeds of some plants do not germinate even under favourable conditions. This is called as dormancy. It is under endogenous control.

Abscisic acid (ABA) is the primary plant hormone responsible for inducing and maintaining seed dormancy to prevent premature germination.

Reasons of seed dormancy:

1. Immaturity of embryo: Embryo is immature at the time of seed shedding. The seed will remain dormant till the embryo becomes mature, e.g., Anemone nemorosa, Ranunculus ficaria.

2. After-Ripening: The seeds require a period of dry storage for developing the ability to germinate, e.g., Wheat, Oat, Barley.

3. Impermeable seed coat: The seed coat is impermeable to water and gases, e.g., Apple, Chenopodium.

4. Hard seed coat: The seed coat is mechanically resistant and does not allow the embryo to grow, e.g., Amaranthus, Lepidium.

5. Germination Inhibitors: They occur in the seed coats and cotyledons of the embryos. The important germination inhibitors causing seed dormancy are abscisic acid, phenolic acid, ferulic acid, coumarin, short fatty acids and cyanogenic chemicals, e.g., Apple, Peach, Ash, Cucurbita, Iris, Xanthium.

So, the correct answer is ‘Hard impermeable seed coat’.