Shankar IAS Test: Plant Diversity Of India - UPSC MCQ

Plant Classification:

1. Herb is defined as a plant whose stem is always green and tender with a height of not more than 1 meter.

2. Shrub is defined as a woody perennial plant differing from a perennial herb in its persistent and woody stem. Not more than 6 meters in height. 3. Tree is defined as a large woody perennial plant having a single well-defined stem with a more or less definite crown.

4. Parasites - An organism that draws a part or whole of its nourishment from another living organism. These plants do not draw moisture and mineral nutrients from the soil. They grow on some living plant called the host and penetrate their sucking roots, called haustoria, into the host plants.

• Extremely high intensity favours root growth than shoot growth which results in increased transpiration, short stem, smaller, thicker leaves.

• On the other hand, low intensity of light retards growth, flowering and fruiting.

• Effect of frost on plants: Killing of young plants - Even a light radiation frost chills the soil resulting in freezing the soil moisture. The plants growing in such soil, get exposed to direct sunlight in the morning, they are killed due to increased transpiration when their roots are unable to supply moisture. This is the main reason for innumerable death of sal seedlings.

• Death of plants due to damage to cells - As a result of frost, water in the intercellular spaces of the plant gets frozen into ice which withdraws water from the interior of the cells. This results in increased concentration of salts and dehydration of cells. Thus coagulation and precipitation of the cell colloid result in the death of the plant.

Let's analyze the given statements regarding the effect of temperature on plants:

1. Excessive high-temperature results in the death of plant due to coagulation of protoplasmic proteins.

   • This statement is correct. High temperatures can lead to the denaturation or coagulation of proteins in the protoplasm, which can cause cell death and, consequently, the death of the plant.

2. It disturbs the balance between respiration and photosynthesis, thereby causes depletion of food resulting in greater susceptibility to fungal and bacterial attack.

   • This statement is correct. High temperatures can disturb the balance between respiration and photosynthesis. Increased respiration rates can lead to a depletion of stored food reserves, making plants more susceptible to diseases and stress factors such as fungal and bacterial attacks.

Since both statements are correct, the answer is:

4. Neither of them

• Refers to the progressive dying usually backwards from the tip of any portion of the plant.

• This is one of the adaptive mechanisms to avoid adverse conditions. In this mechanism, the root remains alive for years together, but the shoots die. E.g. Sal, Red sanders, Terminalia tomentosa, Silk cotton tree, Boswellia serrata.

Causes for dieback

1. Dense overhead canopy and inadequate light

2. Dense week growth

3. Un-decomposed leaf litter on the surface

4. Frost

5. Drip

6. Drought

7. Grazing

• These plants are specialized in trapping insects and are popularly known as insectivorous plants.

• They are very different from typical plants in their mode of nutrition.

• They, however, never prey upon humans or large animals as often depicted in fiction.

• Insectivorous plants can broadly be divided into active and passive types based on their method of trapping their prey.

• The active ones can close their leaf traps the moment insects land on them.

• The passive plants have a ‘pitfall’ mechanism, having some jar or pitcher-like structure into which the insect slips and falls, to be digested eventually. The insectivorous plants often have several attractions such as brilliant colours, sweet secretions and other curiosities to lure their innocent victims.

Invasion and Species Richness:

• The invasions potentially lead to an increase in species richness, as invasive species are added to the existing species pool.

• But it also leads to the extinction of native species, resulting in a decrease of species richness.

• Effects

1. Loss of Biodiversity

2. The decline of Native Species (Endemics).

3. Habitat Loss

4. Introduced pathogens to reduce crop and stock yields

5. Degradation of marine and freshwater ecosystems

Types of Trees: There are two main types of trees: deciduous and evergreen.

(i) Deciduous trees: lose all their leaves for part of the year; In cold climates, this happens during the autumn so that the trees are bare throughout the winter; In hot and dry climates, deciduous trees usually lose their leaves during the dry season.

(ii) Evergreen trees: don’t lose all their leaves at any time (they always have some foliage); They do lose their old leaves a little at a time with new ones growing in to replace the old. An evergreen tree is never complete without leaves.

Annual rings: Inside the trunk of a tree, there are several growth rings.

Each year of the tree’s life, a new ring is added, so it is referred to as the annual rings. It is used to calculate Dendro-Chronology (Age of a tree) and Paleo-Climatology. The number of growth rings can determine the age of a tree. The size of the growth ring is determined in part by environmental conditions - temperature, water availability.

Root types:

Taproot - Primary descending root formed by the direct prolongation of the radicle of the embryo.

Lateral Root: Roots that arise from the taproot and spread laterally to support the tree.

Adventitious Roots: Roots that are produced from the parts of the plant other than the radicle or its subdivision.

• Pneumatophore: It is a spike-like projection of the roots of the swamp/mangrove tree above the ground. It helps the submerged roots to obtain oxygen. Ex: Heritiera spp, Bruguiera spp.

• Haustorial roots are the roots of parasitic plants that can absorb water and nutrients from another plant. • Eg: mistletoe (Viscum album) and dodder.

• Storage roots are modified roots for storage of food or water, such as carrots and beets. They include some taproots and tuberous roots.

Mycorrhiza - structure produced from the combination of the modified rootlet with fungal tissue.