Plant Growth

Science background gives teachers more in-depth information about the phenomena students explore in this unit on matter and energy cycles. Below is an excerpt from the science background information on plant growth. 

Plants and animals have many similarities. Like all living things, plants and animals grow, develop, and reproduce. 

Plant cells have certain structures that animal cells do not, including chloroplasts and a cell wall. They also respond and adapt to their environment. Finally, both are living things, so both need to obtain and use energy.

However, the way in which plants and animals obtain energy is different. As a result, plant cells and animal cells have a few key differences. Plant cells use energy from the sun to make their own food. They are able to do this because plant cells have chloroplasts, which contain a green pigment called chlorophyll. This pigment absorbs sunlight and gives plant cells their green color.

The sunlight absorbed by the chloroplasts begins the process of photosynthesis, which uses the sun’s energy to convert carbon dioxide and water into a kind of sugar called glucose, which the plant uses for energy.

Animals lack chloroplasts and do not photosynthesize, so they must consume plants or other animals for energy. Ninety percent of a plant cell is taken up by the central vacuole, which fills with water and waste from the cell. A plant wilts if its cells lose water in their central vacuoles.

Plant cells also have cell walls, which are stiff fibers that help plants stay rigid and stand up. Animal cells lack cell walls, so they are less rigid and therefore can take many different shapes. Plant cells contain a larger central vacuole than animal cells.

All ecosystems include living things; oxygen and carbon dioxide from the atmosphere; water; and energy from the sun.

Plants are essential parts of all ecosystems. An ecosystem is a community of different organisms that depend on interacting with each other and their physical environment for survival.

Plants are essential to all ecosystems because they are able to capture light energy from the sun and turn it into chemical energy in the form of glucose through photosynthesis. Chemical energy is energy stored in the bonds of atoms and molecules. The glucose produced in photosynthesis also provides the building blocks necessary for proteins, DNA, and all other parts cells need to grow and reproduce.

The leaves are important external structures in photosynthesis. Not only do the cells in plant leaves contain the most chloroplasts, but leaves are also where plants have stomata, which are pores that take in carbon dioxide from the environment and release oxygen. This exchange of gasses in plants is called respiration.

Plants also have roots, which gather water and nutrients from the soil. Roots hold the plant in the ground and withstand the forces of wind and moving water. As the plant grows upward, the roots prevent the plant from becoming unbalanced and toppling over. The stems transport water and nutrients between the roots and the rest of the plant.

Without sunlight, carbon dioxide, and water, plants would not be able to photosynthesize, and without photosynthesis, plants would die. During photosynthesis, plants transform matter that is not food, including air and water, into matter that is food, specifically glucose, allowing the plant to grow and develop.