Lichens

Some of the algae exhibit symbiotic association with the higher plants. Some species of algae and fungi are found in association with each other and they are called Lichens.

Phyllotaxy

The arrangement of leaves on the stem or the branches is known as phyllotaxy. The purpose of phyllotaxy is to avoid overcrowding of leaves so as to expose the leaves maximum to the sunlight for photosynthesis.

pH in living organisms

The fluid in the cells and tissues of plants and animals is usually close to neutrality and the pH of extra-cellular fluids under normal conditions varies from 7.35 to 7.5.

Functions of cell membrane

The cell membrane performs following important functions

(i) It holds the cell together
(ii) The membrane is a selectively permeable boundary which allows water, certain required nutrients and metal ions to pass freely
(ii) It secrete waste products
(vi) It keeps out toxic materials
(v) It contain receptors to bind certain regulatory substances such as hormones which regulate the various metabolic activities.

True Fruit & False Fruit

True Fruit: The fruit, which is derived from ovary of a flower and not associated with any noncarpellary part, is known as true fruit. eg. Tomato,Brinjal, Pea, Mango, Banana etc.,

False Fruit: (Pseudocarp) The fruit derived from the ovary along with other accessory floral parts is called a false fruit. eg. Apple.

Parthenocarpy (Fruits Without Fertilization)

Fertilization acts as a stimulus for the development of ovary into fruit. But there are several cases where ovary may develop into fruit without fertilization. This phenomenon of development of fruit without fertilization is called parthenocarpy and such fruits are called parthenocarpic fruits.

Bract

Bract refers the small leaf like structure inside the flower which is specialized to carry out sexual reproduction in higher plants.A bract is usually situated at the base of pedicel.

Inflorescence

When several flowers arise in a cluster on a common axis, the structure is referred to as an inflorescence.

Simple and compound leaves

Simple Leaf: A leaf is said to be simple in which the leaf blade or lamina is
entire. It may be with incision or without incision. e.g. Mango

Compound leaf: Here the lamina is divided in to a number of leaf like lobes
called the leaflets. The leaflets are borne on a common axis and they do not bear
any axillary buds in their axils.

Four Type of Phyllotaxy(Leaf Arrangement)

Alternate phyllotaxy: In this type the leaves are arranged alternatively in the nodes. There is only one leaf at each node.

Opposite Phyllotaxy: In this type of arrangement two leaves are present at each node, lying opposite to each other.

Ternate Phyllotaxy : In this type there are three leaves attached at each node eg. Nerium

Whorled : In this type, more than three leaves are present in a whorl at each node eg. Alamanda.

Tuber

Tubers are the swollen tips of special underground branches. They are different from rhizomes in that they are stouter, with slender internodes and the adventitious roots are generally absent. The tuber bears many scale leaves with axillary buds in the nodes. Potato is a common example for a tuber.

plasmodesmata

The cell wall is not totally complete around the cell. It is interrupted by narrow pores carrying fine strands of cytoplasm, which interlink the contents ofthe cells. They are called as plasmodesmata.

Epiphytes And lithophytes

A few species of algae which live on another plant or another alga are called as epiphytes and some algae which grow attached to rocks are called as lithophytes.

Benthic

Species that are found attached to the bottom of shallow water along the edges of seas and lakes are called Benthic.

phytoplanktons

The free floating and free swimming minute algae are known as phytoplanktons.

Thallus

In Algae the plant body shows no differentiation into root, stem or leaf or true tissues. Such a plant body is called thallus. They do not have vascular tissues.

Mycology

The study of fungi is known as Mycology. It constitutes a branch of microbiology because many of the handling techniques used, such as sterilizing and culturing procedures are the same as those used with bacteria.

Prions

They are proteinaceous infectious particles. They are the causative agents for about a dozen fatal degenerative disorders of the central nervous systems of humans and other animals.

Viroids

A viroid is a circular molecule of ss RNA without a capsid. Viroids cause several economically important plant diseases, including Citrus exocortis.

Virion

An intact, infective virus particle which is non-replicating outside a host cell is called virion.