Plants Knowledge Organiser Review
Comprehensive Botanical Terminology and Plant Physiology
A plant is defined as a living thing that utilizes energy from sunlight to synthesize its own food. To grow effectively, plants require a specific set of conditions including light, warmth, water, air, nutrients, and adequate physical space. Several key terms define the life cycle and biological processes of plants. A bud is a newly formed flower. Chlorophyll is a green chemical found within leaves that captures sunlight energy to produce food. During the autumn season, most plants cease food production, causing chlorophyll to break down and reveal other colors within the leaves. Fertilisation occurs when pollen and eggs join to create seeds, while fertilizer refers to extra nutrients added to soil to assist growth.
Reproductive components include the flower, which contains the reproductive organs, and the fruit, which develops after the petals fall off and the ovary begins to grow around the developing seeds. Germination is the incipient stage of growth where a tiny root and shoot sprout from a seed. Pollination is the process of transferring pollen from a stamen to a stigma; this can occur via insect pollination, where pollen sticks to an insect's body and is rubbed onto a stigma, or wind pollination, where pollen is carried by air currents.
Structural components include the leaves, which facilitate food production through photosynthesis; the roots, which anchor the plant and absorb water; and the stem or trunk, which supports the plant and transports water and food. Stamen represents the male organ, while the stigma represents the female organ. Nutrients mandatory for healthy growth include nitrogen, potassium, and phosphorus. Seed dispersal describes the methods by which seeds are scattered to regrow, encompassing animal, wind, water, and explosive mechanisms.
Characteristics of Living Things (MRS NERG / MRS GREN)
All living organisms, including plants, share seven vital characteristics often remembered by the acronym MRS NERG or MRS GREN. Movement in animals involves physical relocation, whereas in plants, it involves growing toward light and extending roots into the soil. Respiration is the chemical process of using oxygen to convert food into energy. Sensitivity describes how living things react to their environment. Nutrition is essential as food provides the energy required for living things to survive. Excretion is the process of removing waste products from the body. Reproduction ensures the continuation of the species, with animals having babies and plants growing from seeds. Finally, Growth describes the development of both animals and plants over time.
The Chemical Process of Photosynthesis
Photosynthesis is a chemical process employed by plants and algae to convert energy from sunlight into glucose, which is a carbohydrate. This process takes place primarily within the chloroplasts found in leaves. The requirements for photosynthesis are sunlight, water absorbed from the soil, carbon dioxide taken from the air, and chlorophyll, the green substance responsible for absorbing light energy. The chemical reaction can be summarized by the following equation:
In this process, carbon dioxide gas and water are converted into food in the form of sugar and starch. Oxygen gas is released as a waste product of this reaction.
Specialized Adaptations of Leaves for Photosynthesis
Leaves possess four primary adaptations that maximize their efficiency in photosynthesis. First, they have a large surface area to maximize light absorption. Second, they contain chloroplasts, which are concentrated near the top of the leaf where they receive the most sunlight. Third, leaves are equipped with veins that deliver water to the cells and transport the produced glucose away to other parts of the plant. Fourth, they feature stomata, which are small holes that facilitate gas exchange by allowing carbon dioxide to enter and oxygen to exit the leaf structure.
Functions of Stems and Roots
Stems and roots serve as the primary transport and support systems for the plant. Stems move water from the roots up to the leaves and carry produced food from the leaves down to the roots; they also serve as food storage units. Roots fix the plant firmly in the ground and are responsible for taking in water and essential minerals such as nitrogen, phosphorus, and potassium. Like stems, roots are also used to store food. The health of a plant is directly dependent on absorbing these minerals from the soil.
Plant Anatomy and Reproductive Organs
Flowers are composed of several specialized parts categorized into male and female reproductive organs. The male parts are called stamens, which consist of the anther and the filament. The anther produces pollen containing male sex cells, while the filament supports the anther. The female parts are called carpels, which include the stigma, style, and ovary. The ovary contains ovules, which store the female sex cells. Other floral parts include petals, which are often bright and colourful to attract insects, and sepals, which protect the flower while it is still in the bud stage.
Comparison of Pollination and Fertilisation Processes
Pollination is the transfer of pollen from the stamen to the stigma. Insect-pollinated flowers typically have bright petals, scented sugary flowers, anthers positioned inside the flower, and sticky stigmas to capture pollen from visiting insects. Wind-pollinated flowers usually have dull petals, no scent, exposed anthers on long filaments, and feathery stigmas designed to catch drifting pollen.
Fertilisation is the subsequent process where two sex cell nuclei join. This begins when pollen lands on the stigma. A pollen tube then grows down through the style, allowing the male sex cell nucleus to travel through the tube and join with the female sex cell nucleus inside the ovule. Following fertilisation, a seed forms from the ovule, and the ovary develops into a fruit surrounding the seed.
Seed Structure and Mechanisms of Dispersal
A seed is composed of three main parts: the embryo, which is the internal precursor to the plant; a food store used by the embryo to begin growing when conditions are appropriate; and a hard outer coat for protection. Seeds must disperse or scatter to ensure that new plants grow with less competition from one another for resources.
There are four primary methods of seed dispersal. Wind dispersal uses structures like parachutes or wings to help seeds fly away. Explosion dispersal occurs when seeds are flicked out of a structure. Animal dispersal happens either when fruit is eaten and seeds are dropped in animal waste, or when seeds have hooks that catch on animal coats. Finally, the drop and roll method occurs when fruit hits the ground, splits, and the seeds roll away.
Scientific Investigation of Seed Dispersal
Evaluating the effectiveness of seed dispersal can be done through controlled experiments. One method is a simple drop test from a set height above a starting point to record how far a seed disperses. This experiment should be repeated three times to calculate an average distance. A second method uses a fan to simulate wind dispersal, comparing the average distance dispersed with the fan active versus a control with no wind. In these investigations, maintaining a fair test is crucial. Variables that must be kept constant include the person dropping the seed, the drop height, and the fan speed and distance from the drop point.