Water scarcity

Water scarcity is fast becoming one of the major limiting factors in world crop production. In many areas, poor agricultural practices have led to increasing desertification and the loss of formerly arable lands. Consequently, those plant species that are well adapted to survival in dry climates are being looked at for an answer in developing more efficient crops to grow on marginally arable lands.

Plants use several mechanisms to ensure their survival in desert environments. Some involve purely mechanical and physical adaptations, such as the shape of the plant's surface, smaller leaf size, and extensive root systems. Some of the adaptations are related to chemical mechanisms. Many plants, such as cacti, have internal gums and mucilages which give them water-retaining properties. Another chemical mechanism is that of the epicuticular wax layer. This wax layer acts as an impervious cover to protect the plant. It prevents excessive loss of internal moisture. It also protects the plant from external aggression, which can come from inorganic agents such as gases, or organic agents which include bacteria and plant pests.

Researchers have proposed that synthetic waxes with similar protective abilities could be prepared based on knowledge of desert plants. If successfully developed, such a compound could be used to greatly increase a plant's ability to maintain health in such adverse situations as inadequate water supply, limited fertilizer availability, attack by pests, and poor storage after harvesting.

1. This passage deals mainly with

(A) desertification

(B) decreasing water supplies

(C) factors limiting crop production

(D) developing efficient plants

2. Which of the following is a mechanical or physical mechanism that desert plants use?

(A) The plant's shape

(B) The small root system

(C) The vast leaf size

(D) The high water consumption

3. Which is one of the ways in which the epicuticular wax protects the plant?

(A) It helps the plant to avoid excessive moisture intake.

(B) It helps the plant to attack aggressors.

(C) It releases gases against plant pests.

(D) It guards against bacteria.

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Date: 2015-12-12; view: 1262; Нарушение авторских прав