Reading. 3.Read the text and find out the words from ex

3. Read the text and find out the words from ex. 2 and translate the sentences with those words.

A Chance for Seeds to Germinate

Fortunately for the understory, the dormant trees sleep until later into the spring. By the time the trees arose themselves, the understory has enjoyed several weeks of early springtime growth, and seeds that survived winter in the soil have had an opportunity to germinate.

Seed germination requires warm soil temperatures and plentiful water, both of which occur at this time of year. If, by chance, seeds should germinate in summer, the dim light on the forest floor often causes seedlings (newly germinated, baby plants) to grow with spindly stems and poorly developed leaves. Their chances for survival are slight.

The best time of year for seeds to germinate in the forest is early spring. By the time the canopy closes, the young plants are strong, well established, and able to survive for several months in the shade.

When a seedling grows in full sun, its stem is short and thick, the leaves are closely spaced, and they are green and fully expanded. The same plant in heavy shade has a thin, stretched-out stem bearing small, pale leaves.

Plants spend a lot of time and energy making seeds, because it is from them that the next generation grows. Many forest species have seeds with a built-in system that promotes germi­nation in spring and prevents wasteful germination under the canopy in summer. This system depends on red light reaching seeds on the forest floor.

Sunlight is composed of the various colors seen in a rainbow. When light enters a leaf, the red and blue parts of the visible spectrum are trapped by leaf pigments. (The pigments channel the light's energy into food production in photosynthesis.) Under a heavy leaf canopy, very little red light reaches the ground, but green wavelengths pass right through the leaves. That is why leaves look green.

Many seeds possess special chemicals that, when stimulated by red light, start the seeds' germination. This happens in springtime in the forest, before the dominant trees have opened their new leaves. When the sun's red wavelengths reachand penetrate into the soil, the waiting seeds are stirred into activity.

In winter and spring in a deciduous forest, most of the sunlight reaches the soil between the trees' bare branches. When the snow melts and the soil warms in spring, red wavelengths in sun­light waken dormant seeds. In summer, the leaf canopy filters the sunlight. Very little red light penetrates to the forest floor. The green wavelengths that do reach the ground have no effect on seed germination.

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