Ответ по предмету Математика: Расстояние между пунктами A и B - 210 км.Из них одновременно навстречу друг другу выехали две автомашины и встретились через полтора часа.Скорость одной из них была 60 км|ч.Найдите скорость второй машины ..

Предмет: Английский язык, автор: akmaralkosylbaj

4.3. Прочитайте и переведите текст.
Leaf Structure
Leaves vary in shape, size, and arrangement on a plant. You can identify many plants just by studying their leaves. But whether a leaf is needle shaped, as in pine trees, or broad and flat, as in maple trees, almost all leaves have the same important function. A leaf is a plant's food-manufacturing site, the place where photosynthesis occurs. The structure of a leaf allows it to capture the sun's energy and build complex molecules from raw materials.
The leaves of most dicots have two main parts, a blade and a petiole. The flattened blade is the main part of the leaf. The petiole is a slender stalk that attaches the blade to a stem. In many dicot leaves, the petiole continues into the leaf blade to form the midrib of the blade. A midrib is a major vein that runs down the middle of a blade. Other leaves have several large ribs − or major veins − that branch out through the blade from the petiole. Ribs help support a leaf. All the veins of a leaf contain xylem tubes and phloem tubes. Xylem tubes supply leaf cells with water and minerals. Phloem tubes transport manufactured food from the leaf to other parts of the plant.
Unlike dicot leaves, most monocot leaves do not have petioles. The leaf blade narrows toward the base of the leaf. The blade attaches directly to the stem. Instead of having a branching network of veins, most monocots have veins that run nearly parallel to each other. Although dicot and monocot leaves differ in appearance, both types of leaves manufacture food for the plant.
Dicot leaves can be either simple or compound. If a leaf consists of a single blade, it is a simple leaf. The leaf edge can be indented in various ways.
If the leaf blade is divided into two or more bladelike parts, the leaf is compound. Each part of a compound leaf is called a leaflet. Telling a simple leaf apart from a leaflet is often difficult. However, a bud forms at the base of a leaf where the petiole joins the stem. A bud never forms at the base of a leaflet.
Compound leaves grow in two distinct patterns: pinnate and palmate. Pinnately compound leaves have leaflets attached along a single midrib. Leaves of ash trees are an example of pinnately compound leaves. The leaflets of palmately compound leaves radiate from a central point, like the fingers of a hand.
The structure of some leaves enables them to carry out special functions other than photosynthesis. Some plants, called succulents have thick, fleshy leaves which store water or food. An onion plant is one type of succulent. The onion bulb is made up of food storage leaves, which are attached to a very small stem. When you eat an onion, you are eating leaves.
Some leaves are modified to catch insects. Some plants have pitcher-shaped leaves that are usually filled with water and digestive enzymes. Stiff downward pointing hairs line the inside of the "pitcher". These hairs allow insects to crawl down into the pitcher but not out again.
The leaves of a few plants produce plantlets which have small leaves and roots. These tiny plantlets separate from the leaf and fall to the ground where they can take root and form new plants.
Ответьте на вопросы по тексту (упр. 4.3):
1.What is the main function of a leaf?
2.What is the difference between dicot and monocot leaves?
3.What is a midrib?
4.What do all the veins of a leaf contain?
5.How do simple dicot leaves differ from the compound ones?
6.What do pinnately compound leaves attach to?
7.Where do the leaflets of palmately compound leaves radiate from?
8.What other functions can leaves fulfill?
9.How can leaves be modified in order to catch insects?
10.What role do plantlets play in the formation of new plants?
8.Pinnately compound leaves radiate from the central point.
9.Succulents have fleshy leaves which can store water or food.
4.8 Расположите пункты плана в логической последовательности на основании содержания текста (упр. 4.3):
1.Simple and compound leaves
2.General information about leaves
3.Special types of leaves

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