All About Plants 

by Inamdar Habiba

• Plants

• Plants Structure

• Word to know

• Plants Development

• Plants disease
• How Do Plants Help the Environment

 Plants

A plant is any organism in the kingdom Plantae. Kingdoms are the main divisions into which scientists classify all living things on Earth. The other kingdoms are: Monera (single-celled organisms without nuclei), Protista (single-celled organisms with a nucleus), Fungi, and Animalia (animals). The scientific study of plants is called botany.

A general definition of a plant is any organism that contains chlorophyll (a green pigment contained in a specialized cell called a chloroplast) and can manufacture its own food. Another characteristic of plants is that their rigid cell walls are composed mainly of cellulose, a complex carbohydrate that is insoluble (cannot be dissolved) in water. Because of the vast number of plants that exist, cellulose is the most abundant organic compound on Earth. Biologists have identified about 500,000 species of plants, although there are many undiscovered species, especially in tropical rain forests.

Plant structure

Those plants that produce seeds are the dominant and most studied group of plants on the planet. The leaves of these plants are all covered with a cuticle, a waxy layer that inhibits water loss. The leaves have stomata, microscopic pores, that open during the day to take in carbon dioxide and release oxygen during photosynthesis (process by which sunlight is used to form carbohydrates from carbon dioxide and water, releasing oxygen as a by-product).

Words to Know

Carbohydrate: A compound consisting of carbon, hydrogen, and oxygen found in plants and used as a food by humans and other animals.

Chlorophyll: Green pigment found in chloroplasts that absorbs sunlight, providing the energy used in photosynthesis.

Chloroplasts: Small structures in plant cells that contain chlorophyll and in which the process of photosynthesis takes place.

Meristem: Special plant tissues that contain actively growing and dividing cells.

Phloem: Plant tissue consisting of elongated cells that transport carbohydrates and other nutrients.

Photosynthesis: Process by which sunlight is used by plants to form carbohydrates from carbon dioxide and water, releasing oxygen as a by-product.

Stomata: Pores in the surface of leaves.

Transpiration: Evaporation of water in the form of water vapor from the stomata.

Xylem: Plant tissue consisting of elongated cells that transport water and mineral nutrients.

Leaves are connected to the stem by veins, which transport water and nutrients throughout the plant. There are two special types of cells in this vascular system (the vessels that carry water and nutrients): xylem and phloem. Xylem (pronounced ZEYE-lem) are mainly responsible for the movement of water and minerals from the roots to the stems and leaves. Phloem (pronounced FLOW-em) are mainly responsible for the transport of food, principally carbohydrates produced by photosynthesis, from the leaves throughout the plant. The vascular system of plants differs from the circulatory system of animals in that water (in the form of vapor) evaporates out of a plant's stomata (a process called transpiration), whereas an animal's blood is recirculated throughout the body.

The roots of a plant take up water and minerals from the soil, and also anchor the plant. Most plants have a dense, fibrous network of roots, and this provides a large surface area for the uptake of water and minerals.

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Plant development  

As a plant grows, it undergoes developmental changes. Most plants continually produce new sets of organs, such as leaves, flowers, and fruits. In contrast, animals typically develop their organs only once and these organs merely increase in size as the animal grows.

A plant begins its life as a seed. Various environmental cues such as sunlight, temperature changes, and the presence of nutrients signal a seed to germinate (grow). During early germination, the young seedling depends upon nutrients stored within the seed itself for growth. As the seedling grows, it begins to produce chlorophyll and turn green. Most plants become green only when exposed to sunlight because the production of chlorophyll is light-induced.

In contrast to animals, whose bodies grow all over as they develop, plants generally grow in specific regions, referred to as meristems. A

Meristem is a special tissue that contains actively growing and dividing cells. Apical meristems are at the tips of shoots and roots and are responsible for elongation of a plant. Lateral meristems are located along the outer sides of the stem of a plant and are responsible for thickening of the plant.

Plant diseases

Plant diseases can be infectious (transmitted from plant to plant) or noninfectious. Noninfectious diseases are usually referred to as disorders. Common plant disorders are caused by a shortage of plant nutrients, by waterlogged or polluted soil, and by polluted air. Too little (or too much) water or improper nutrition can cause plants to grow poorly. Plants can also be stressed by weather that is too hot or too cold, by too little or too much light, and by heavy winds. Pollution from automobiles and industry and the excessive use of herbicides (to kill weeds) can also cause noninfectious plant disorders.

Infectious plant diseases are caused by living microorganisms that infect a plant and rob it of nutrients. Bacteria, fungi, and viruses are the living agents that cause plant diseases. None of these microorganisms are visible to the naked eye, but the diseases they cause can be detected by the symptoms of wilting, yellowing, stunting, and abnormal growth patterns.

Some plant diseases are caused by rod-shaped bacteria. The bacteria enter the plant through natural openings, like the stomata of the leaves, or through wounds in the plant tissue. Once inside, the bacteria plug up the plant's vascular system and cause the plant to wilt. Other common symptoms of bacterial disease include rotting and swollen plant tissues. Bacteria can be spread by water, insects, infected soil, or contaminated tools.

About 80 percent of plant diseases can be traced to fungi, which can grow on living or dead plant tissue. They can penetrate plant tissue or grow on the plant's surface. Fungal spores, which act like seeds, are spread by wind, water, soil, and animals to other plants. Warm, humid conditions promote fungal growth.

Viruses are the hardest pathogens (disease-causing organisms) to control. Destroying the infected plants to prevent spreading to healthy plants is usually the best control method. While more than 300 plant viruses have been identified, new strains continually appear because these organisms are capable of mutating (changing their genetic makeup). Viruses are spread by contaminated seeds and sucking insects (aphids, leafhoppers, thrips) that act as carriers of the virus. The symptoms of viral infection include yellowing, stunted growth in some part of the plant. Leaf rolls and narrow leaf growth are other indications of viral infection. The mosaic viruses can infect many plants. Plants infected with this virus have mottled or streaked leaves.

How Do Plants Help the Environment 

Oxygen Provision:Without plants, humans and animals would have less fresh air to breathe. Through the process of photosynthesis, plants release oxygen back into the atmosphere. What you may not have known is that plants from the ocean are what provide most of the air that we breathe². These single celled plants that thrive in the ocean are also known as phytoplankton. Green terrestrial plants make up the rest of atmospheric oxygen that’s essential for the survival of living organisms³.

 Carbon Sinks:During this time of climate uncertainty, it’s important to realize the role plants can play to help mitigate the effects of climate change. One of the biggest environmental issues the world faces today is the burning of fossil fuels which has resulted in high levels of carbon dioxide in the atmosphere. Although climate change is a reality the world must face, society is still highly reliant on fossil fuels to supply energy needs. This is where plants come in to play. Terrestrial and oceanic plants are considered carbon sinks because of their ability to store carbon dioxide from the atmosphere⁴. Important carbon sink ecosystems include: grasslands, boreal forests, tropical rainforests, peat bogs, wetlands, coral reefs and coastal ecosystems.

 
 

Habitat:Plants are also important because they provide habitats for wildlife and humans. For example, many species of birds rely on trees and shrubs for habitat, whether they live in the crevices of trees or build nests on branches. Healthy habitats also provide wildlife with roosting cover and shelter from predators⁵. Unfortunately, habitat loss is considered one of the causes for species endangerment and extinction. Forest ecosystems continually face deforestation in the form of fires, clear cutting for agriculture and ranching, and unsustainable logging⁶. Plants play a pinnacle role in many of the Earth’s ecosystems so their presence is important to ensure wildlife and ecosystem health.

Food:Since plants are considered primary producers, they play an important role in feeding the Earth’s wildlife and humans. Herbivores, such as deer, rely on plants directly to meet their dietary needs, while carnivores, such as lions, feed on animals that also feed on plants for their survival. And omnivores, such as humans, rely on both. Whether directly or indirectly all wildlife and humans rely on plants for sustenance.

Water Cycle Regulation: About 10% of the moisture in the atmosphere is released by plants through the process of transpiration⁷. Plants uptake water through their roots and release water vapour through small pores on the underside of their leaves. Through this process of transpiration plants also help circulate water from the soil back into the atmosphere. Not only that, but plants help stabilize bodies of water such as rivers, lakes and streams.  Plant roots improve soil stability, prevent landslides, and keep these ecosystems intact.

Despite the many benefits that plants provide, one of the environmental issues we face is environmental degradation. The Earth’s ecosystems are subject to deforestation, development and resource extraction. Because of the many ways plants help humans and the environment, ecosystems and plants need to be protected. During this time of environmental uncertainty, it’s important that we don’t take their presence for granted.