Botany lecture notes

Secretory Tissue System in Plants (Structure, Classification and Functions + PPT)


secretory cells

Secretory Cells and Tissues in Plants
(Structure and Classification of Secretory Tissue System in Plants with Examples)

What are plant secretions?

Most of the plants release many substances from their cell cytoplasm to the exterior and they are called as Plant-secretions. Among these secretions, some are beneficial to the plant and some are not. The beneficial substances secreted from the plant parts are called as secretions. The chemical composition of plant secretions highly varies. The secretions may be water, nectar, salt, tannins, resins, latex, gums, digestive enzymes, hormones etc.

Secretory Cell/Tissue

Cells or tissue associated with or facilitate the secretion is termed as the secretory cell or secretory tissue. The structure, arrangement and the origin of secretory cells/tissues highly varies.

Classification of Secretory Tissues

Ø  The secretory tissue is broadly classified into two categories based on their position in the plant body. They are

(I). External secretory tissue

(II). Internal secretory tissue

Continue reading

Botany lecture notes

General Characters of Gymnosperms (Lecture Notes with PPT)


characteristics gymnosperms

Gymnosperms – Characteristics
(Morphology, Reproduction and Life Cycle of Gymnosperms with PPT)

Gymnosperms are primitive seed-producing plants of Spermatophytes (Phanerogams). They are ‘Naked-Seed’ Plants. The term is derived from two Greek words: ‘gymnos’ meaning naked and ‘sperma’ meaning seeds. They are characterized by naked ovules (i.e., ovule without the ovary). The ovules of Gymnosperms are borne directly on the surface of the megasporophyls. Unlike Angiosperms, in Gymnosperms the seeds are NOT enclosed in the fruit. Thus the Gymnosperms are also known as “Phanerogams without ovary”.

seeds of gymnosperms

General Characteristics of Gymnosperms

Distribution

Ø  Gymnosperms are a small ancient group of seed plants consisting of 83 genera and 1080 species.

Ø  Distribution: Temperate and Tropical regions.

Ø  Gymnosperms were originated in the Paleozoic Era (541 – 252 million years ago).

Ø  They were the dominant plants of Jurassic and Cretaceous periods of the Mesozoic era.

Continue reading

Botany lecture notes

Hydathode or Water Stomata–Structure and Functions (Short Notes)


water stomata notes

Hydathode – Water Stomata
(Structure and Functions of Hydathodes)

What are Hydathodes?

Hydathodes are specialized pores (openings) particularly present on the leaf margins, which exudes or secretes drops of water. The exudation of water as drops from the tip or margin of the leaves is called guttation. The process of guttation is facilitated by the hydathodes.

Ø  They are also called as Water Stomata because they structurally resemble stomata and they facilitate guttation (secretion of droplets of water from the pores of plants).

Ø  Hydathodes are commonly found in Angiosperms, especially in grasses.

Ø  They are also present in some other plants such as water hyacinth, balsam, roses, Hibiscus and rarely in some non-angiospermic plants.

Continue reading

Difference between Tropic Movements and Nastic Movements – Comparison Table


Tropic vs Nastic Movments

Tropic Movements vs Nastic Movements
Similarities and Differences between Tropic Movements and Nastic Movements in Plants

Tropic movements and Nastic movements are the two types of induced or paratonic movements of curvature in plants.

Tropic movements: The paratonic (induced) movement of growth is called tropic movements. Here the stimuli are external and unidirectional. Example: phototropic movements (movement towards the light) geotropic movements (movement towards gravity), chemotropic movements (movement towards chemicals) etc.

What is Phototropism

Nastic movements: The paratonic movements of variations are called nastic movements. Here the stimuli are external and diffused (not unidirectional). Example: nyctinastic movements (movements in response to darkness), Seismonastic movements or Thigmonastic movements (movements in response to touch) etc.

What is Nastic Movment

The present post discusses the Similarities and Differences between Tropic Movements and Nastic Movements in Plants with a Comparison Table.

Continue reading

Biostatistics Study Materials

Statistical Data /Variables – Types and Classification (Biostatistics Short Notes)


What is Data or Variable

Statistical Data / Variables – Introduction
(Classification of Statistical Data / Variable – Numeric vs Categorical)

What is ‘data’ or ‘variable’?

Ø  Data is a set of values of qualitative or quantitative variables.

Ø  In biostatistics (also in statistics) data are the individual observations.

Ø  The scientific investigations involve observations on variables.

Ø  The observations made on these variables are obtained in the form of ‘data’.

Ø  Variable is a quantity or characteristic which can ‘vary from one individual to another’.

Ø  Example: Consider the characteristic ‘weight’ of individuals and let it be denoted by the letter ‘N’. The value of ‘N’ varies from one individual to another and thus, ‘N’ is a variable.

Ø  Data and variable are not exact but used frequently as synonyms.

Ø  The variables can also be called as ‘data items’.

Ø  Majority of the statistical analysis are done on variables.

Type of Variables in Statistics

Statistical variables can be classified based on two criterion (I) Nature of Variables and (II) Source of variables

I. Classification of variable based on Nature of Variables

Ø  Based on the nature of variables, statistical variables can be classified to TWO major categories such as (1) Numerical and (2) Categorical.

Continue reading