PLANTS

A living organism of the kind exemplified by trees, shrubs, herbs, grasses, ferns, and mosses, typically growing in a permanent site, absorbing water and inorganic substances through its roots, and synthesizing nutrients in its leaves by photosynthesis using the green pigment chlorophyll.

Parts of a plant

A typical plant has different parts in its body. Different parts of the plant are the roots, stem, leaves, flowers and fruits. The parts which are present underground are the roots. Parts which are present above the ground are stem, leaves, buds, flowers, fruits and seeds.

                                                                                                        

Root

The roots of a plant are mostly seen underground and look brown in color. The tiny thread-like structures over the roots are the root hairs. The tip of the root is covered by root cap which is preventive in function. Root and the root hairs form the root system.

Features of root

Root grows towards the soil and away from the light. Hence, it is called as geotropic structure.
Root does not possess green color pigment, the chlorophyll. It cannot produce food.
Root does not bear leaves, buds or flowers.
Roots along with their root hairs absorb water and minerals from the soil.

Functions of root

They hold the plant firmly in the soil, thereby serving as an anchor to the plant.
They absorb water and nutrients from the soil required for the growth of the plan
Some roots also store starch and sugars in them
Some roots also help in respiration. They possess special structures called as pneumatophores.
Some roots have useful bacteria in them to increase the soil fertility with nitrogen content.

Types of roots

Roots are of two types - tap root and fibrous roots.
Tap root is a primary root that grows more or less straight down into the soil, and is tapered towards the end. It is found in many of the plants. It is also called as true root. Smaller roots that branch out from the tap root are called as lateral roots. Examples of plants with tap roots are hibiscus, carrot, turnip and sunflower.
Fibrous roots are a group of lateral roots arising at the base of the stem. In the plants bearing fibrous roots, tap root slowly weakens and replaced by bunch of roots arising from the base of the stem. These bunch of roots form the fibrous roots. Examples of plants with fibrous roots are banana, grass and onion.

Modifications of roots

Roots in many plants are modified to perform additional functions by some modifications.
Storage roots are the roots modified to store food in them. e.g. Carrot, turnip, radish, sweet potato etc.
Respiratory roots are the roots modified for respiration. The plants in mangroves have roots with special structures called as pneumatothodes to obtain more oxygen.
Parasitic roots are the roots which arise from the stem and absorb nourishment from the host plant. e.g. Cuscuta.

Climbing roots are the roots which help the plant to climb and cling on to the support. e.g. Money plant, betel.
Reproductive roots are the roots which help in the process of producing the offspring.
Prop roots are the roots which offer support to huge structure of the tree. e.g. Banyan tree

Stem

The stem is the part of the plant seen above the ground. It bears the leaves, flowers and fruits of a plant. It is almost green or woody. It grows towards the sunlight. It moves away from the ground.

Features of stem

They support the entire plant to stand as a whole.
They are always phototropic. i.e. they grow towards light.
Stem has nodes separated by inter nodes. Stem bears branches, leaves, flowers and fruits.





Functions of stem

Stem helps in transportation of absorbed water and nutrients through vascular tissue from roots to leaves

Stem also transports food from the leaves to different storage organs.

Stem exposes leaves to light and help them in performing the process of photosynthesis.

The stem bearing leaves helps in the process of transpiration. Transpiration is the process by which plants release excess water in the form of water vapor through minute openings in the leaves called as stomata.

Sometimes stem can store food which is mostly underground.

Stem can store water by becoming fleshy as in desert plants.

Stem can perform photosynthesis when leaves are reduced or absent as in desert plants.

Modifications of stem

Stems in many plants are modified to perform additional functions by some modifications.

Storage of food: In some plants, underground stem is modified to store food in the form of starch. Three types of underground modifications of stem are tubers (e.g. Potato), rhizome (e.g.Ginger) and bulb (e.g.Onion).

Photosynthesis: In some desert plants, leaves are absent or reduced to spines. Here, the stem performs photosynthesis to synthesis food.

Protective structures: In some plants like rose, stems are modified into thorns to protect the plant from being eaten by animals.

Supportive structures: In climbing plants, stems are modified sometimes into structures which twine around the support.

Storage of water: In some plants like cactus and jade, stems become fleshy and succulent to store water.

Leaves

Leaves are the structures which develop on branches. These are green coloured structures rich in chloroplasts. As they have chlorophyll in them, they are considered to be food factories of the plant. Photosynthesis occurs in the leaves. Each leaf bears a bud in its axil.

                                                                                                  Parts of leaf

The point of attachment of the leaf to the node on the stem is called as leaf base.

Leaf bears a stalk with which it is attached to the stem. It is called as petiole.

The flat part of the leaf exposed to light is called as lamina.

A thin structure which extends from the leaf base to the tip on the lamina is called as mid-vein. Many small thread like structures extend from the mid rib to the leaf margin. These are called as vein lets. Arrangement of veins on the lamina of the leaf is called as venation. Veins help in transportation of food and water.

Two types of arrangement of veins on the leaf are parallel venation and reticulate venation.

Types of leaves

Leaves can be simple leaf or compound leaves.
Simple leaf is a single leaf with undivided lamina.
Compound leaf is a leaf which has divided lamina into a number of leaflets. The central structure called rachis bears all the leaflets.

Arrangement of leaves

Leaves are arranged in different patterns at the node on the stem. Arrangement can be alternate, opposite, whorl etc.
Alternate leaves are the ones which arise one at a node.

Opposite leaves are the leaves which arise as two at a node.
Whorl type of arrangement includes three or more leaves arise at a node.

Structure and surface of the leaf

Leaf has two surfaces namely, dorsal surface and ventral surface. Dorsal surface is the upper surface which is exposed to sunlight. It has number of chloroplasts having lot of chlorophyll in them. Upper surface of the leaf is dark green in colour.
Leaf has many pores called as stomata on both of its sides. These stomata help in exchange of gases like oxygen and carbon dioxide. Stomata also help in loss of excess water by the process of transpiration.

Functions of leaf

Leaves are the food factories of the plant which help in the process of photosynthesis to synthesise their food. They make use of raw materials like carbon dioxide and water in the presence of chlorophyll and sunlight.
Leaves lose excess water by the process of transpiration. Transpiration cools the body of the plant by regulating the temperature.

Modifications of leaf

In weak stemmed plants, leaves are modified into special structures which twine around a support. These are tendrils. These offer support to the plant while climbing up.
In some plants like onion, leaves are modified to store food. These are termed to be scaly leaves.
In some desert plants like cactus, leaves are reduced to spines so as to reduce loss of water through transpiration. These spines are also called as thorns. Thorns protect these plants from grazing animals.
In some insectivorous plants, leaves are modified into pitchers where they are used to trap insects. These insects can be digested inside the body of the plant. In this way, plants obtain nitrogen from animals.

Flower

Flower is a reproductive structure of the plant. The different parts of a flower include sepals, petals, stamens and pistil. Flower helps the plant to give rise to new plants by the process of sexual reproduction.

Parts of a flower

The green leaf-like structures surrounding the bud are called as sepals.
The colored parts of a flower are called as petals. These help in attracting insects.
The male reproductive part of a flower is called as stamen. It carries pollen grains.
The female reproductive part of a flower is called the pistil. It carries ovules.

Fruits

Fertilization is the union of male and female cells in a flower to produce a fruit. Fruit is basically the fertilized ovary. This grows in size to store sugars. Ovules develop into seeds. So, fruits enclose seeds.

Posted by: Rea Ritchel J.de Arao

Puberty: Changes for Females

Puberty – it's a crazy time. Your body's changing, and so is everything else. But, what is causing all these changes?

You know how everyone says that puberty is all about raging hormones? It's kind of true. Hormones that were hibernating suddenly awaken and signal your body to enter puberty. You might think this doesn't mean a lot, but hormones cause the changes that are associated with puberty.

• timing of puberty
• breasts
• pubic hair
• growing
• acne

Timing of Puberty

Puberty starts at different times and lasts for different periods of time for everyone. It can start as early as 8 years of age to as late as 13 years of age. The sequence of puberty – from breast development to complete physical maturation – may take a year and a half or last as long as 6 years.

This is sometimes very difficult for girls as some of their peers may have entered and completed puberty before they have even started. However, there is no way to slow or speed up the process, but puberty happens to everyone, so never fear, it will happen to you!

You may have heard that girls mature more quickly than guys, and that is somewhat true, since girls usually enter puberty about 2 years earlier than boys.

Below is a general time line for physical changes that occur during puberty (for girls):

Puberty Event		Age at which it happens
Growth of breasts		8-13
Growth of pubic hair		8-14
Body Growth		9 1/2-14 1/2
First Period		10-16 1/2
Underarm Hair		2 years after pubic hair shows up
Acne		Around the same time as underarm hair

Remember, puberty is not the same for everyone, so some girls will grow pubic hair before they develop breasts, and that is absolutely normal.

More Information on Each Physical Change

Breasts

Breast development begins between 8 years of age and 13 years of age and continues through puberty.

Breast development starts with the flat area around the nipple (areola) becoming enlarged and some breast tissue forming under the nipple. When breast development is complete, each breast is distinct and the areola no longer appears swollen.

Breast size varies from woman to woman, and there is no way to try to make your breasts larger or smaller other than going through plastic surgery, which is not always a very safe or healthy alternative.

Pubic Hair

Pubic hair starts along the vaginal lips, the outer opening of your private parts. The hair becomes darker and coarser and grows like an inverted triangle. Sometimes, the hair spreads to the insides of thighs, as well.

Growing
Puberty also causes you to go through a growth spurt, which results in an average growth of about 3.5 inches a year.

Your head, hands, and feet are the first things to grow. Then you grow in your arms and legs, and finally your torso and shoulders catch up with the rest of your body.

If it's any consolation, everyone goes through that awkward phase, so you are not alone! Height growth is, of course, accompanied by an increase in weight.

This weight gain is perfectly normal and a part of puberty. Without gaining this weight, you cannot grow taller, develop breasts, or get your first period.

Acne
Finally, underarm hair begins to grow, and your sweat and oil producing glands also start developing, which eventually results in acne when these glands are clogged.

In order to avoid breakouts, you should wash your face twice daily. If you still regularly break out, you may want to speak to a dermatologist.

Respiratory system

A complete, schematic view of the human respiratory system with their parts and functions.

The respiratory system (called also respiratory apparatus, ventilatory system) is a biological system consisting of specific organ and structures used for the process of respiration in an organism. The respiratory system is involved in the intake and exchange of oxygen and carbon dioxide between an organism and the environment. In air-breathing vertebrates like human beings, respiration takes place in the respiratory organs called lungs. The passage of air into the lungs to supply the body with oxygen is known as inhalation, and the passage of air out of the lungs to expel carbon dioxide is known as exhalation; this process is collectively called breathing or ventilation. In humans and other mammals, the anatomical features of the respiratory system include trachea, bronchi, bronchioles, lungs, and diaphragm. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveoli (air sacs) in the lungs.
In fish and many invertebrates, respiration takes place through the gills. Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants also includes anatomical features such as holes on the undersides of leaves known as stomata.

The Parts of a Flower

Peduncle: The stalk of a flower. Receptacle: The part of a flower stalk where the parts of the flower are attached. Sepal: The outer parts of the flower (often green and leaf-like) that enclose a developing bud. Petal: The parts of a flower that are often conspicuously colored. Stamen: The pollen producing part of a flower, usually with a slender filament supporting the anther. Anther: The part of the stamen where pollen is produced. Pistil: The ovule producing part of a flower. The ovary often supports a long style, topped by a stigma. The mature ovary is a fruit, and the mature ovule is a seed. Stigma: The part of the pistil where pollen germinates. Ovary: The enlarged basal portion of the pistil where ovules are produced.