Sunday, November 14, 2010

10 Things About Dormancy

1. Why go to sleep? In dormancy, metabolism virtually comes to a standstill to conserve energy. Dormancy is triggered by environmental changes, such as decreasing temperatures, but living things are also affected by light. In plants, dormancy can also be triggered by drought and heat, such as when lawn grasses turn brown in midsummer.

2. Hibernation. Plants aren't the only living things to utilize dormancy. Animals hibernate, decreasing heart rates by as much as 95%. Hibernating animals prepare for this state by building up reserves of fat to provide them with the fuel needed to get through the winter. (Is that why many humans gain weight before Christmas?)

3 . Diapause. Certain animals, such as roe deer (native to Britain) and marsupials, and some insects enter a state called Diapause. For higher animals, this results in a delay in the attachment of the embryo to the uterine lining, ensuring offspring are born in spring. Insects that enter this state simply suspend their development and growth.

4. Aestivation is almost the same as hibernation, but has opposite causes. Aestivation results from exposure to very hot or very dry conditions. Garden slugs, snails and worms are subject to this type of dormancy.

5. Brumation is similar to hibernation but it happens with reptiles, which can go months without food. They can stay in brumation for as long as eight months. They will occasionally "awake" long enough to get a drink of water, but they do not eat in this state. Brumation can be triggered by cold and reduction of sunlight.

6. Viruses can also go dormant, remaining quiescent in the cells of the human body for long periods. An example of this would be the V aricella zoster virus which cause chickenpox, then sleeps for years until it awakens as shingles ( Herpes zoster). Bacteria can also go dormant.

7. How do they know? Some plants have a kind of biological clock to alert them about when to take a rest. Houseplants, for example, often stop growing when the days get shorter, even though the temperature never varies. You should stop watering as much now and avoid fertilizing.

8. Seeds can also go dormant. When a ripe seed is given all the right conditions but fails to germinate, it is considered dormant, not dead. A 1,300 year old lotus seed was germinated after recovery from a dry lakebed in Northern China. Do you still believe in the end of the world?

9. Deciduous trees and shrubs, as you know, also go dormant, losing their leaves and halting photosynthesis. But they do still need some water in the soil to survive, so be sure to water in late October or when the tree has lost all its leaves. These trees store food reserves of sugars n their roots. (Cold-hardy deciduous trees will not survive indoors in winter, so bonsai growers let them go dormant before storing them in a cool place for the season.)
10. Evergreen trees. Evergreens don't go completely dormant in winter by they slow right down, retaining some moisture in their needles which are protected from desiccation by a waxy coating. They continue to photosynthesise at a reduced rate (which is why their leaves look grey or black as the temperature drops). Help them out by keeping late winter sun glare from drying out their needles. Build a sunscreen (but don't let the burlap touch the needles because it acts like a wick, drawing water away from the tree). You can even simply rough up the snow in front of your evergreen on a south facing lot to deter the drying effects of the sun's reflection off the snow.