Science Q&A

How do seeds for annuals survive winter?

New York TimesNovember 4, 2012 

Q: The packets for annual seeds say to plant them after any danger of frost. How do so many annuals seem to make it through the cold months?

The packet warning is aimed at protecting the vulnerable seedlings, not the relatively invulnerable seeds.

In general, the seeds for annual plants are adapted to sprout each year when conditions return to ideal after a season of stress, whether cold or drought. The annual plant dies off, leaving the seeds as something like life rafts to carry the plant’s genetic heritage across to the next generation.

Many annual plants are prolific producers of seeds, ensuring that at least some of them will be in the right place at the right time, usually in spring but sometimes in autumn. Favorable conditions include not just soil temperature and texture but also moisture and light.

Some seeds can lie dormant for years until the conditions are right, and some need a period of moist pre-chilling, called stratification, to prepare them for germination. Others need to have their tough coatings scratched, or scarified, to sprout.

Milk & tea

Q: Does adding milk to tea destroy its antioxidants?

Adding milk to tea may reduce some of its healthful properties, studies show.

Next to water, tea is the most widely consumed beverage in the world. Chock-full of antioxidants, vitamins and other compounds, tea has been linked in a variety of studies to stronger immune function and reduced cell damage. Some research suggests tea may prevent cavities, improve blood sugar levels and perhaps provide cardiovascular benefits.

In many parts of the world, the custom is to serve tea with milk. But in a study published in The European Heart Journal, researchers had 16 healthy adults drink cups of freshly brewed black tea, black tea mixed with a small amount of skim milk, or boiled water. Then the scientists measured the effects on vascular function.

Compared with water, black tea “significantly improved” arterial function, the researchers found, “whereas addition of milk completely blunted the effects of tea.”

The scientists repeated similar tests in mice and found the same results, which they speculated may be a result of proteins in milk binding to and neutralizing antioxidants.

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