Internal Structure of Angiospermous Plants

The plant body is made up of cells which organize themselves to form Tissues. Tissues organize to form tissue system. The study of the internal structure of plants is known 'Plant Anatomy'. 1.1 Tissue: -It is a group of similar or dissimilar cells performing a common function and having a common origin. Types of tissues:-Two types -Meristematic and Permanent. 1. Meristematic Tissues(Meristems): -These are a group of cells which are in a continous state of division. These tissues divide to form new cells which differentiate to give rise to permanent tissues. Types of meristems: -  A. On the basis of origin & development, these are of three types:  i. Promeristem: -It is a group of initial cells that lay down the foundation of an organ or plant part. ii. Primary meristem: -It is formed from promeristem. Primary body, tissue differentiation and their organization' results from activity of primary meristem. iii. Secondary meristem: -These are formed secondarily from permanent tissues which acquire the power of division. B. Depending on their position in plant body, these are of three types: i. Apical meristem: -Present at the tips of stem, root and their branches. Responsible for growth in length. It is dome like with outer layer-Tunica& inner mass-Corpus. It has promeristem which differentiates into three regions: - * Dermatogen: -Outermost layer; gives rise to epidermis of the stem. In roots, it forms 'Calyptrogen' which is a mass of tissues which forms root cap. In dicots-it forms epilema of roots. * Periblem: -next to dermatogen. Forms cortex of root and stem. * Plerome: -lies internal to periblem. Cells elongate here and form procambuim which later forms Xylem & Phloem. ii. Intercalary Meristem: -It is located in between the regions of permanent tissues. These cells divide and continue to add new cells. These are responsible for growth in length. Present at bases of node, internodes and leaves. iii. Lateral Meristem:-These occur on sides & increase the girth of plant.

Understanding Life

INTRODUCTION:  Some organisms are living e.g. Bacteria, animals whereas some organisms are non-living. e.g. bricks ,stones. The main difference between the two is of ‘life’. Defining ‘life’ is difficult. Example of virus supports it. A virus doesn't have a life but when it is inside a cell, it becomes active and multiplies showing that it has life. (1.1) ORGANISMS SHARE SOME BASIC AND UNIFIED CHARACTERISTICS : Living organisms differ from each other in many aspects but they have many things in common like all are built up of cells, which have same structure and function. All have same basic characteristics governed by same physical laws like order, energy utilization, regulation, growth, development, reproduction etc. Common feature of living organisms: * Have fixed shape and size. * Are highly organized. It is because of this organization that living being is called ‘organism’. Cell is the basic structure of organization and there are different levels of organization. * All show metabolism i.e. series of biochemical reactions keep going inside cell. Reactions involving breakdown of compounds are ‘catabolic reactions. Reactions involving synthesis of compounds are ‘anabolic reactions’. * Use energy for metabolism and growth. * Show development and reproduce. * Maintain constant body temperature (Homeostasis) * Adapt to environmental changes. * Gradually evolve into new species.