Introduction

A plant is a living thing. This means that plants reproduce, grow and feed. Plants live on water, air, and sunlight.

Plants are broken into two main groups, flowering and non-flowering.

• Flowering Plants - Most of the plants around us are flowering plants. Flowering plants have roots, stems, leaves, flowers and fruits.
• Non- flowering Plants - These do not have flowers and include plants like algae, ferns, fungi and mosses.

Parts of a Plant

In order to discuss plants in a meaningful way, it is important to know the proper names for the all the different parts a plant can have. Flowering plants have four major part types:

• Leaves
  Leaves make all the food for the plant. They do this by changing light, water and gases into food. This process is called photosynthesis.
  
  

• Stems and branches
  Stems and branches hold up the leaves and space the leaves out. This helps the plant to get the light it needs.

• Roots
  Roots help fix the plant to the soil or to other plants. Roots take in water and nutrients.

• Flowers
  Flowers contain the male and female parts of the plants. Successful pollination of the flower can result in the production of fruit and seeds.

Roots

All roots are responsible for:

• anchoring the plant to the ground
  
• extracting water and minerals from the soil

In a typical root we can distinguish the following parts:

1. Primary root - the thickest . It grows downwards.

2. Secondary roots - arise from the primary root. They are not as thick as the primary one. They go sidewards.

3. Root cap - is a kind of protection the roots end with. It is designed to drill the soil and it is able to guide the root growth by perceiving gravity.

4. Root hairs - are minute filaments roots are covered with. They absorb water and nutrients from the soil.

Stems

• supporting leaves and flowers physically
  
• holding the leaves and flowers in the best position for food gathering and reproduction
  
• using xylem and phloem to transport materials from areas of plenty to areas of need in various parts of the plant
  
• storing nutrients for future use

bud - an underdeveloped and unelongated stem composed of a short axis with compressed internodes, a meristematic apex, and primordial leaves and/or flowers. 

terminal bud - a bud at the tip of a stem responsible for terminal growth. 

axillary bud or lateral bud - buds along side the axis of a stem; they were produced by the terminal bud during growth; once they grow out and form a lateral stem they become terminal buds of the lateral branch. 

flower bud - a bud containing a floral meristem which develops into flowers; usually larger than vegetative buds. 

leaf scar - a scar marking the former point of attachment of a leaf or petiole to the stem. 

internode - the part of the stem between nodes 

node - part of stem marking the point of attachment of leaves, flowers, fruits, buds and other stems. 

lenticel - rough areas on stems (and some fruits, ex. apple) composed of loosely packed cells extending from the cortex through the ruptured epidermis; serve as "breathing pores" for gas exchange. Only occur on young stems. 

growth rings - bud scale scars from the last terminal bud; they denote flushes of growth (usually per year). Can be used to age stems because usually 1 set of growth rings is produced per year on temperate trees in the Temperate Climatic Zone.

Leaves

All leaves are responsible for:

• absorbing the sun's rays
  
• the majority of photosynthetic production (which can take place in any green part of a plant),
  
• taking in carbon dioxide and releasing oxygen and water vapor (breathing)
  
• removing waste products from the plant
  
• using osmotic pressure to draw water up from the roots

Parts of a leaf

Photosynthesis

Photosynthesis is the process in which carbon dioxide (CO₂) and water (H₂O) are used to produce  carbohydrates and evolve oxygen (O₂) in the presence of light and chlorophyll; the net result is light energy (radiant energy) is converted into chemical energy in the form of fixed carbon compounds (carbohydrates).

Flowers

All flowers are responsible for one important function: reproduction.

The Flower:
The flower is the reproductive unit of some plants (angiosperms). Parts of the flower include petals, sepals, one or more carpels (the female reproductive organs), and stamens (the male reproductive organs).

The Female Reproductive Organs:
The pistil is the collective term for the carpel(s). Each carpel includes an ovary (where the ovules are produced; ovules are the female reproductive cells, the eggs), a style (a tube on top of the ovary), and a stigma (which receives the pollen during fertilization).

The Male Reproductive Organs:
Stamens are the male reproductive parts of flowers. A stamen consists of an anther (which produces pollen) and a filament. The pollen consists of the male reproductive cells; they fertilize ovules.

Pollination

Pollen must fertilize an ovule to produce a viable seed. This process is called pollination, and is often aided by animals like bees, which fly from flower to flower collecting sweet nectar. As they visit flowers, they spread pollen around, depositing it on some stigmas. After a male's pollen grains have landed on the stigma during fertilization, pollen tubes develop within the style, burrowing down to the ovary, where the sperm fertilizes an ovum (an egg cell), in the ovule. After fertilization, the ovule develops into a seed in the ovary.

Most flowering plants (ninety percent) depend on animals to make the vital pollen-grain delivery. The remaining flowering plants rely on wind and some-times splashing raindrops to ferry pollen, but this is a less precise method. Pollinating animals do the job for a reward: food, usually in the form of nectar.

Fruit and Seeds

The fruit is that part of a plant which is in charge of protecting the seeds and guarantee their dispersal. It becomes as a result of the fertilization inside the carpel, which produce the ripening of the ovary walls that will create the fruit. Some fruits, however, have another origin, deriving from the flower receptacle or some other parts of the flower.

We have many kinds of fruits but the most typical fruit shows the following parts:

• The pericarp is the external part of a fruit. It is all that surrounds the seed. It is divided into:
• The exocarp is the outer covering. In an apple, for instance, it is what we know as the "skin".
• The mesocarp is the middle covering. In a peach what we ordinary call the "flesh".
• The endocarp is the inner covering , in many cases the stiffened part normally covering the seed. In a plum , for example, what we commonly know as the "stone".

Types of Fruit

There are many different types of fruit that we can eat:

• Soft fruits, eg raspberry, blackberry, redcurrant, strawberry, bilberry.
• Citrus fruits, eg orange, lime, lemon, kumquat, grapefruit.
• Stone fruits, plum, apricot, peach, lychee, cherry, mango.
• Fleshy fruits, eg apple, papaya, pineapple, pear, banana
• Vine fruits, eg grape, water melon, cantaloupe

Seeds

The seed is enclosed inside the endocarp.This is a typical seed. We can see the following parts:

• The radicle is the part of the embryo which emerges first. Once outside it develops into a main root, producing root hairs and secondary roots.
• - The plumule is like a leaf in its early development.
• - The hypocotyl is the space between the radicle and the plumule. It develops into a stem.
• The endosperm is the food supply contained in the seed. This is sometimes included in the cotyledons, which either achieve the function of primary leaves or food storage, even both of them in some cases.
• According to the number of cotyledons, we classify plants in two groups: monocotyledons or monocots and dicotyledons or dicots. In the first group we find so important plants as cereals, palms, lilies, tulips or orchids. The members of the second group are more numerous and comprises most of the trees and flowers.
• The seed coat or testa - is the outer layer of the seed.
• The micropyle is a litle pore on the seed coat , through which, apart from entering the sperm, the seed absorbs water to begin germination.