Conduction

Water and minerals are transported throughout a plant by the help of a transport system.Water absorbed by the roots of the plant helps in transportation, food production and cooling.

Conducting System of the plant consists of Xylem and Phloem tissues.

Xylemtransports water and minerals (absorbed by roots) in an upward direction, i.e., from roots to stem and leaves.Xylem tissues are composed of cells called tracheids and vessels. Tracheids are long, thin spindle–shaped cells. Water and minerals flow through pits from one tracheid to another. On the other hand, vessels are perforated long cells with tubular passages. Tubular passages are joined end to end with each other to form a channel.

The process of transportation of absorbed water and minerals (sap) from the root to the top of the plant is called ascent of sap. Due to continuous inflow of water, pressure develops in the root. It is called root pressure.

Phloem is a living tissue that is mainly responsible for the conduction of food produced in leaves.Through phloem tissues, the transport of food occurs in upward and downward directions from leaves to all parts of the plant.Cells join end to end to form long tubular channels called sieve tubes.

Plants absorb water continuously from the soil in large quantities, however, only a small amount of water is used by plants while the remaining evaporates from the leaves. Loss or evaporation of water from the leaves (stomata) in the form of water vapours is called transpiration.

Stomata are more on lower surface of the leaves. Therefore, leaves loose more water from the lower surface.

Sunlight, temperature, wind and humidity affect the process of transpiration.

Transpiration brings about cooling effect and regulates plant temperature. It also helps in maintaining concentration of sap.
The raw materials that plants need for various synthetic activities and for the production of energy are termed as plant nutrients.
Depending upon the quantitative requirements of plants, mineral nutrients are broadly classified into macronutrients and micronutrients.

Macronutrients are required in comparatively large amount for normal growth and development in plants.Nitrogen, Phosphorus, Potassium, Carbon, Hydrogen, Oxygen, Calcium, Magnesium, Sulphur are some macronutirents.

Micronutrients are required in minute amount for proper growth and development in plants.Boron, Copper, Chlorine, Manganese, Molybdenum, Nickel, Zinc and Iron are some micronutrients.

These nutrients act as structural elements, components of energy related compounds, enzyme activators or inhibitors, etc.
Deficiency of these nutrients causes chlorosis, necrosis, stunted growth, dieback of shoots, molting, etc.

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  • Q1

    Plant cooling occurs due to-

    Marks:1
    Answer:

    Transpiration

    Explanation:

    Transpiration is the process, where plants absorb water through the roots and then give off water vapor through stomata in their leaves. It has two main functions: cooling the plant; and pumping water and minerals to the leaves for photosynthesis.

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  • Q2

    Which of the following is a macronutrient?

    Marks:1
    Answer:

    Ca

    Explanation:

    Out of the given elements, calcium is a macronutrient, whereas copper, magnese and zinc are micronutrients.

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  • Q3

    Premature leaf fall is due to the deficiency of-

    Marks:1
    Answer:

    Phosphorus

    Explanation:

    In plants, premature leaf fall occurs due to deficiency of phosphorus. Potassium and magnesium deficiencies also cause chlorosis on older leaves, but in phosphorus deficiency chlorosis usually does not retain a distinct interveinal pattern, as is typical of potassium or magnesium deficiencies.

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  • Q4

    Stomata usually open because they have-

    Marks:1
    Answer:

    low concentration of CO2

    Explanation:

    Low concentration of CO2 causes stomata to open. If CO2-free air is blown across stomata in darkness, they will open. High concentration of CO2 causes stomata to close.

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  • Q5

    Which of the following are not micronutrients?

    Marks:1
    Answer:

    P, Mg

    Explanation:

    Phosphorus and magnesium are macro-nutrients.

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