The plant body consists of two basic parts: the shoot system and the root system.
The Root System * Underground (usually) * Anchor the plant in the soil * Absorb water and nutrients * Conduct water and nutrients * Food Storage

The Shoot System * Above ground (usually) * Elevates the plant above the soil * Many functions including: * photosynthesis * reproduction & dispersal * food and water conduction * Note: the shoot system includes the leaves and the reproductive organs, although these will be covered in more detail separately

The shoot system includes organs such as leaves, buds, stems, flowers, and fruits and usually it develops above ground.
The functions of the shoot system include * Photosynthesis, * Reproduction, * Storage, * Transport, * Hormone production.

Photosynthesis,
The most important characteristic of plants is their ability to photosynthesize, photosynthesis is the process in which plants, green algae, and some bacteria convert sunlight, water, and carbon dioxide into oxygen and in the sugars that they need for growth. Light-sensitive pigments called chlorophylls and closely-related pigments like carotenoid are essential to the photosynthetic process. Thanks to photosynthesis plants are autotrophs, which means that they sustain themselves without eating other organisms or substances derived from other organisms. It sustain practically all living being directly or indirectly, making it vital to life on Earth.

Reproduction
In biology reproduction is the sexual or asexual process by which organisms generate new individuals of the same species; procreation.  sexual (or generative) reproduction is the process by which organisms create descendants through the combination of genetic material. These organisms have two different adult sexes, male and female.
 Asexual (or vegetative) reproduction is the biological process by which an organism creates a genetically similar copy of itself without the combination of genetic material with another individual. Most plants are capable of vegetative reproduction

* Storage
Here the food is stored for the plants to feed from

* Transport
Takes water from the root to the leaves

Hormone production
Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, when moved to other locations, in other locations of the plant. Hormones also determine the formation of flowers, stems, leaves, the shedding of leaves, and the development and ripening of fruit. Plants, unlike animals, lack glands that produce and secrete hormones. Instead, each cell is capable of producing hormones. Plant hormones shape the plant, affecting seed growth, time of flowering, the sex of flowers, senescence of leaves, and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity, and even plant death. Hormones are vital to plant growth, and, lacking them, plants would be mostly a mass of undifferentiated cells. So they are also known as growth factors or growth hormones.

The root system includes roots as well as modified stem structures such as tubers and rhizomes and usually it develops underground.

The functions of the plant root system include:
1. Anchorage and support. The plant root system anchors the plant in the soil and provides physical support. Redwood trees (a gymnosperm) about 100 meters tall have stood erect for thousand years only because millions of individual fibrous roots dig into the ground, even though the depth of penetration is only up to about 5 meters. In general, however, taproot system provides more effective anchorage such that they are more resistant to toppling during storms.
2. Absorption and conduction. The plant root system absorbs water, oxygen and nutrients from the soil in mineral solution, mainly through the root hairs. They are capable of absorbing inorganic nutrients in solution even against concentration gradient. From the root, these are moved upward. Plants with a fibrous root system are more efficient in absorption from shallow sources.
In the desert plants called phreatophytes like the mesquite, the roots seek permanent underground water reserves. These plants are water indicators and knowledge of such plants has been put to use by digging wells where they grow (Went and The Editors of Life 1963).
3. Storage. The root serves as storage organ for water and carbohydrates as in the modified, swollen roots of carrot, sweet potato (camote) and yam bean (sinkamas). Fibrous roots generally store less starch than taproots. Some roots are capable of storing large amounts of water; the taproots of some desert plants store more than 70 kg of water (Moore et al. 2003). (Click to read Starchy Root Crops, Tuber Crops and Corm Crops)
4. Photosynthesis. Some roots are capable of performing photosynthesis, as in the epiphytic orchids and aerial roots of mangrove.
5. Aeration. Plants that grow in stagnant water or other watery places have modified roots called pneumatophores to which oxygen from the air diffuses.
6. Movement. In many bulb- and corm-forming plants, contractile roots pull the plant downward into the soil where the environment is more stable.
7. Reproduction. The plant root system also serves as a natural means of perpetuating a species. In mature Norfolk Island pine and certain plants, clonal seedlings or offshoots are commonly seen growing profusely around the trunk from horizontally growing roots. Likewise, new plants emerge from left-over tuberous roots after harvest in fields grown to sweet potato and yam bean (Pachyrhizus erosus). As a rule, plants with a fibrous root system are easier to transplant than those with tap roots.