Unit - 10

Plant Physiology

Q1) Describe plant physiology?

A1) A biological science that concerned with the plants and their general patterns governing the life processeshappening in plants. 

Plant physiology is a branch of study in Botany that deals with the functions of the plant and the various physiological processes that occur in plants. Specifically, it is a show a descriptive study of structure and variation of plants at the cellular and molecular level leading to ecological, physiological and biochemistry related aspects of plants exploration.

As plants evolved on land, they required various methods to survive with the separation of carbon dioxide and water.

Plant physiology gives an account of the different parts of the plant and how they function.

Q2) Explain the importance of leaves roots and stem in plants?

A2) Leaves

Leaves are the most important organ of the plant. The leaves help in photosynthesis. They have many veins and have the pigment chlorophyll; the leaves grow in a variety of shapes and sizes. They are the primary centre of photosynthesis where the food is prepared.

Stem

The stem is the backbone of the plant they provide support and structure to the plant. The stem is of different type in many species, they are branched or may be a single stem, they perform many important functions such as plant growth, compete and survive in different environments, etc.

Roots

The roots are the part of the plant that help the plant to fix in the soil, they help the plant to stand firmly. It helps in absorption of water and nutrients from the soil. Thus, they are an important part of the plant.

Q3) Define Respiration?

A3) All living organism, containing plants, get their energy necessary for their survival from a series of chemical reactions termed respiration. The process of Respiration needs glucose to start the reactions which are changed into energy and later produce carbon dioxide and water as byproducts.

The method by which cells get chemical energy by the consumption of oxygen and the liberation of carbon dioxide is called respiration.in order to carry on respiration, plant cells require oxygen and a means of disposing of carbon dioxide just as animals cell do. In plants, every par such as root stem executes respiration as plants do not possess any particular organs for exchange of gases.

The method of respiration is written as:

Oxygen+ glucose------water + carbon dioxide with energy.

As plants do not have any specialized organs like lungs to breathe, plants do not breathe they respire, they respire with the help of lenticels and stomata that exist on stems and leaves which carry out the function of exchange of gases.

Q4) Explain the function of Xylem and phloem?

A4) The xylem and the phloem make up the vascular tissue of a plant and transports water, sugars, and other important substances around a plant. What is commonly referred to as ‘sap’ is indeed the substances that are being transported around a plant by its xylem and phloem.

The separation between plants that have veins and plants that do not is one of the great divides within the plant kingdom. This separates plants into vascular and non vascular plants. Most plants have xylem and phloem and are known as vascular plants but some more simple plants, such as mosses and algae, do not have xylem or phloem and are known as non-vascular plants.

Phloem and xylem are closely associated and are usually found right next to one another. One xylem and one phloem are known as a ‘vascular bundle’ and most plants have multiple vascular bundles running the length of their leaves, stems, and roots.
Xylem tissue is used mostly for transporting water from roots to stems and leaves but also transports other dissolved compounds. Phloem is responsible for transporting food produced from photosynthesis from leaves to non-photosynthesizing parts of a plant such as roots and stems.

Q5) Explain the types of Respiration?

A5) Types of respiration

There are two kinds of respiration which are categorize on the basis of presence or absence of oxygen.

Aerobic respiration

The respiration that occurs in the presence of oxygen is called aerobic respiration due to air that which has oxygen. The aerobic respiration contains utilization of oxygen for the breaking of chemical bonds in Glucose to liberate energy in high volumes. It is the central source of energy for all organisms, Animals and plants that use oxygen for respiration are aerobes. Mostly all the animals have aerobic respiration.

C6H12O6+6O2-6CO2+6H2O+Energy

Aerobic respiration takes more energy because a complete breaking of glucose takes place during respiration with the use of oxygen. 

Anaerobic Respiration

The respiration that occurs in the absence of oxygen is known as anaerobic respiration. In this process, the incomplete oxidation of food substance is being made by carbon dioxide CO2 and alcohol (OH). Beside this other organic matter such as citric acid, oxalic acid, lactic acid etc. are produced.

Glucose-Alcohol+CO2+ (Energy)

Anaerobic respiration yields much less energy due to the partial breakdown of Glucose happens in anaerobic respiration in the absence of oxygen. All the organisms which gain energy by Anaerobic respiration can exist without oxygen. E.g., yeast can live in the absence of oxygen, yeast respires anaerobically and all through this process, yeast transforms into alcohol, therefore it is used to make alcohol and in fermentation industry.

Q6) Explain Transpiration and its importance?

A6) Transpiration, is a plants loss of water, mainly through the stomata of leaves. Stomatal openings are present on the leaves, these stomata have openings that allow carbon dioxide inside the leaf and oxygen is given out through the leaves through photosynthesis. Therefore, Transpiration is a very important step in plants that accompany the real function of stomata. It has been observed that transpiration provides the energy to transport water in the plant. Excessive transpiration can be extremely injurious to a plant. When water loss exceeds water intake, it can retard the plant’s growth and ultimately lead to death by dehydration

Transpiration was first measured by Stephen hales (1677–1761), an English botanist and physiologist. He noticed compared to animals’ plants “imbibe” and “perspire” significant amounts of water compared to animals and therefore help measuring the emission of water vapour by plants. He found there was an upward flow of dissolved nutrients and water from the roots and that transpiration occurred from the leaves and he proposed that Transpiration occurred through leaves. Modern research has shown that as much as 99 percent of the water taken in by the roots of a plant is released into the air as water vapour.

Q7) Define Stomata and its function?

A7) The primary sites for Transpiration are the leaf stomates, stomata consist of two guard cells that have small openings. The opening and the closing of the stomata is controlled by the guard cells, this also further depends on environmental stimulus and the guard cells can regulate transpiration to reduce loss of water from leaves. Stomata’s can sometimes close and transpiration can decrease due to darkness and internal water deficit, some factors that help opening of stomata are illumination, ample water supply, and optimum temperature open stomates and increase transpiration. Many plants close their stomates under high temperature conditions in order to reduce evaporation or under high concentrations of carbon dioxide gas, when the plant likely has sufficient quantities for photosynthesis

Q8) How do few plants adapt themselves to reduce water through transpiration?

A8) There are a few other adaptations which also help to reduce water loss through transpiration. Physically, plants that live in areas of low humidity have leaves with less surface area therefore evaporation is minimal or limited. On the other hand, plants in humid areas, which receive very less sunlight, have large leaves to receive sufficient sunlight and keep water loss low. Many desert plants have minute leaves that eliminate water loss during the dry season the leaves are deciduous during drought periods, Sunken stomata waxy cuticle, trichomes and other leaf adaptations help reduce transpiration rates by keeping the surface of the leaf cool, however cacti lack any form of leaves, when conditions are very hot and dry some plants including many succulents, open their stomates during the night to take in carbon dioxide and close them during the day time.

Q9) Explain Mineral Nutrition and the role of nutrients?

A9) The most naturally occurring inorganic nutrient that is found in soil and food is called as Mineral Nutrition, it is essential for the proper functioning of animal and plant body. They are the most vital elements necessary for the body. Both the plants and animals require minerals essentially. For example, for the manufacture of protein and cell division the nutrient Zinc is absolutely essential.

Nutrients which are required by plants in very small amounts are termed as Micro Elements or macronutrients. Some of them include copper, magnesium, iron, boron, chlorine, and molybdenum.

Plants which require Nutrients in large amounts are termed as Macronutrients. Some of them include nitrogen, sulphur, carbon, phosphorus, potassium, calcium, and magnesium.

Role of Nutrients

Q10) What are Micro and Macronutrients specify?

A10) Micronutrients

Functions of some of the Micronutrients are stated below:

Copper

Manganese

Zinc

Macronutrients

Functions of certain macronutrients are stated below:

Phosphorous

Nitrogen

Potassium

Potassium is the only monovalent cation that is necessary for plants. It acts as an enzyme activator including DNA polymerase. The deficiency of potassium leads to Mottled chlorosis.