Botany lecture notes

Heterospory and Seed Habitat in Pteridophytes (Short Notes)

Significance of Heterospory

Heterospory and Seed Habitat
(Origin of Seeds and Seed Habitat in Vascular Plants from Heterospory)

Heterospory is the production of two or more types of spores

Heterospory is a condition of the production of more than one type (usually two) of spores in a single plant. These two types of spore differ in their formation, structure and most importantly its functions and sexuality. In Pteridophytes, these two spores are called as Microspores and Megaspores.

(1). Microspores:

Microspores are small sized spores produced in large numbers inside the microsporangium. They are male spores which on germination produce male gametophyte.

(2). Megaspores:

Megaspores are comparatively large spores produced in limited numbers (1 to 4) inside the megasporangium. They are female spores which on germination produce the female gametophyte.

Learn more: Difference between Microspores and Megaspores

The production of two types of spores with different sexuality was first evolved in Pteridophytes. Even though, the condition of heterospory is now represented only by eight living species of Pteridophytes, they are Selaginella, Isoetus, Marsilea, Salvinia, Azolla, Pilularia, Regnellidium and Platyzoma.

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Botany lecture notes

Mutation Breeding Technique for the Improvement of Crop Plants (with PPT)

what is mutation breeding

Mutation Breeding
(Induced Mutations for Crop Improvement)

What is mutation?

Mutation is the “Sudden heritable change in an organism”. Mutation may be the change in gene, chromosome or plasmagene (genetic material inside mitochondria and chloroplasts. The mutation produced by change in the base sequence of gene is called point mutation or gene mutation. The gene mutation may be further classified as transition, transversion, deletion, duplication or inversion. Chromosomal mutations are the change in chromosome structure. The change in the structure of chromosome can occur as a result of large deletion, inversion, duplication, translocation and change in chromosome number. Most of the mutations are lethal to the organism. A very small number of mutations are beneficial to the organism. Additionally, by the use of mutation inducing agents, a breeder can induce desirable changes in the genetic constitution of plants and thereby he can improve the performance of a cultivated variety.

Mutation Breeding

Definition: “The utilization of induced mutations in crop improvement is called mutation breeding”

The term mutation breeding was first coined by Freisleben and Lein in 1944 to refer to the deliberate induction and development of mutant lines for crop improvement.

Spontaneous and Induced mutations:

(1). Spontaneous mutation:

Mutation occurs in nature are called spontaneous mutation. Spontaneous mutation occurs in the organism without any treatment at low rate in the nature. The frequency of spontaneous mutation is 10-6 (one in 10 lakhs). Different genes in and organism show different mutation rate.

(2). Induced mutation:

Mutations induced in an organism by treatment with physical or chemical mutagen are called induced mutations. The agents which are used to induce mutation are called mutagens. Certain genes in an organism promote the mutation of other genes nearby in the chromosomes. For example, the gene Dt in Chromosome number 9 of maize increases mutation rate of other genes.

Characteristics of Mutation:

Ø  Mutations are generally recessive; Dominant mutations do occur in nature.

Ø  Mutations are generally harmful to organism; small percentage of mutation is beneficial.

Ø  Mutation occurs at random in the chromosome, may occur in any gene.

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Botany lecture notes

Parenchyma Cells in Plants: Structure, Classification and Functions (PPT)

functions of parenchyma

(Structure, Classification and Function of Parenchyma)

What is simple tissue?

Ø  The tissue (a group of cells with particular function) composed of single type of cells.

Ø  Three types of simple tissue system in plants:

(1).  Parenchyma

(2).  Collenchyma

(3).  Sclerenchyma

What are the characteristics of Parenchyma (Parenchymatous Cells)?

Ø  Parenchyma is a simple permanent tissue.

Ø  They are living cells which contains plenty of water.

Ø  Cells are nucleated with prominent nucleus.

Ø  They are thin walled cells.

Ø  Cell wall composed of cellulosic primary cell wall only.

Ø  No lignin deposition in the cell wall of parenchyma.

Ø  Parenchymatous cells are relatively undifferentiated

Ø  Parenchyma is the least specialized along simple permanent tissues in plants.

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Ecology Lecture Notes

Xerophytes: Ecological Adaptations with PPT

ecological adaptations of xerophytes ppt

Xerophytic Adaptations of Plants
(Ecological Adaptations of Desert Plants)

What are xerophytes?

Ø  Xerophytes (xerophytic plants) are plants growing in dry habitats (xeric conditions) where the availability of water is very less.

Ø  Xeric habitat: places where water is NOT present in adequate quantity.

Ø  Xerophytes are the characteristic plants of deserts or semi-deserts areas.

Ø  Xerophytes can also grow in mesophytic conditions.

Ø  Xerophytes can tolerate:

$.  Extreme dry condition

$.  Low humidity

$.  High temperature

$.  High wind-flow

Ø  Three types of xeric habitats occurs on the earth:

(1). Physically dry habitat: the water retaining capacity of the soil very low and climate is dry (Example: a desert).

(2). Physiologically dry: water is present in excess, but not in the absorbable conditions or the plants cannot absorb it (Example: high salt water, high acidic water and high cold water, water as snow).

(3). Physically and physiologically dry: water present as mist, plants cannot absorb water from the atmosphere directly. (Example: mountain slopes)

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Ecology Lecture Notes

Characteristics of Hydrophytes with PPT (Classification and Adaptations)

Water plants adaptations PPT

Hydrophytes: Classification and Adaptations
(Morphological, Anatomical and Physiological Adaptations of Aquatic Plants)

What is an adaptation?

Ø  “Any feature of an organism which enables it to exist under conditions of its habitat is called adaptation”.

Ø  Adaptations are for withstanding adverse conditions of environment and to utilize the maximum benefit of the environment (nutrition or conditions).

Ø  Adaptations in plants may be in:

1.   Morphological features

2.   Anatomical features

3.   Physiological characters

4.   Reproductive characters

Classification of plants based on water relation (Warming, 1990)

(1). Hydrophytes: plants growing in or near water.

(2). Xerophytes: plants adapted to survive under very poor availability of water.

(3). Mesophytes: plants growing in an environment which is neither very dry nor very wet.

What are hydrophytes?

Ø  Hydrophytes (aquatic plants, water plants) are plants growing in or near water.

Ø  These plants are adapted to survive in excess of water in their surroundings.

Ø  Greek: Hudor = water; Phyton = plant: water plant

Ø  Examples: Utricularia, Vallisneria, Hydrilla, Chara, Ceratophyllum, Trapa

Ø  Aquatic plants are the producers of the aquatic ecosystem.

Ø  They fix sunlight and ensures the survival of an aquatic ecosystem.

Ø  Even though plants originated in water, except algae, most of the aquatic plants are evolved from their mesophytic relatives.

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