teacher resources: The Basics of Botany what is a plant? I Flowers: flowers attract animals and provide nectar while completing the needed process Although this may seem like an easy answer, a of pollination. plant may be defined differently depending on I Fruits: fruits protect and disperse the seeds group the people. An elementary school teacher inside. may describe a plant as a “living green thing”, a high school teacher may narrow this definition, I Seeds: Seeds are young plants that continue and a plant scientist may have a technical un - the lifecycle. derstanding of a plant. All these definitions serve a purpose and the definition needs to be what are the parts of a plant? modified depending on the audience. The plant body can be divided into three main Plants are “green things”, which means they carry parts: roots, stems, and leaves. Some botanists out a process called photosynthesis. There are refer to the latter two as “shoots”. Most many green, photosynthetic organisms, but students have a good understanding of what some of these, such as bacteria, are not plants. these look like, but the distinction between Algae are a group of organisms that may be these can sometimes be fuzzy. considered plants by some teachers, but would Consider that some plants have stems that be called protists by scientists. This distinction is resemble roots (e.g. ginger), or stems that probably not important to school children; the resemble leaves (e.g. prickly pear cactus). It is important message is that these organisms use important that students understand that plants the sun to make their own food. In contrast, a need certain materials to survive; these may be group such as fungi, although plant-like, do not obtained by roots in some plants but through make their own food and should not be consid - the stems or leaves in another. The determina - ered plants. For the purposes of this handout, we tion of whether a plant part is a root or stem, will concentrate on plants that live on land and such as the potato, seems to be less important. are familiar to students of all ages and levels. The flexibility, adaptability of plants and the Defining Characteristics function of their parts should be the focus. I Roots: absorption of water and minerals; anchorage of plant to the soil; usually found underground I Stems: support of leaves, flowers, and fruits; transportation of water –minerals from roots to leaves; found above and below ground. I Leaves: site of photosynthesis or food-mak - ing; usually found above ground. page 1 teacher resources: The Basics of Botany what are roots? I Respiration : Some swamp or flooded plants Roots serve as the most fundamental organ to produce roots or “knees” that grow up and out health of most plants. The root or radicle is the of the water, allowing the roots to exchange first plant part to appear from a seed. Roots act to gases in this oxygen-free environment ( e.g . bald anchor the plant and absorb water and nutrients cypress, mangrove) for photosynthesis; these are called true roots. I Support : Specialized adventitious roots called True roots are usually divided into two forms: prop, stilt, and buttress roots can be found on fibrous and tap . Some plants have a mass of tropical trees that experience frequently string-like, fibrous roots ( e.g . grasses); others flooding ( e.g . mangrove). have a large, main taproot with smaller side roots I Photosynthesis : In rare cases, plants have (e.g . oaks, carrots). Sometimes roots “sprout” green, aerial roots that photosynthesize from the side of a stem, like in a vine; these are (e.g . orchids). called adventitious roots. A plant with an underground stem will have adventitious roots. Functions of roots what are stems? I Absorption : Absorption of water and nutrients Stems are the most basic organs on plants. are one of the primary functions of roots. Roots Simple examples of a stem are twigs, branches, absorb water through a passive, physical process. and the trunk(s) of a tree. Stems can range Water being released from leaves is linked to from hard & woody to soft & green other water molecules in the plant like a chain. (herbaceous) , but almost all stems serve a As the water is pulled out of the leaf into the at - supportive function on a plant. mosphere, the chain pulls new water molecules Most people know what a stem looks like, but up through the stem and into the roots. some plants make the distinction difficult. I Anchorage : Roots also act to anchor the plant Some plants have small stems, or underground in the soil or on rock. Thus, roots act as the stems (rhizomes) , or leaf-like stems, or stem- major supportive organ for all other organs. like leaves or sometimes lack stems altogether. I Conduit : Roots (like stems and leaves) serve as Although we make neat and clear categories the initial pipeline for water that is needed in the called stems, leaves, and roots, this distinction plant. Sugars (energy) are also transported down can be blurred. Grasses are a good example in to the actively growing portions of the root. which the difference between leaf and stem is not easily observable. I Storage : Most roots store some quantity of sugars, water, or toxic chemicals (like leaves and stems), but some roots are quite large and fleshy storage organs ( e.g . carrots). page 2 teacher resources: The Basics of Botany what are stems? (continued) I Protection : In many plants, branches have been modified over time to serve as protection Functions of stems against large animals; these are called thorns. Many trees have thorns ( e.g . hawthorn, crabap - I Structure : Most stems serve the role of support in a plant. For example in a tree, the trunk sup - ple, honey locust). Note: Cacti and rose bushes ports the branches, which support the twigs, do not have thorns, because these are not mod - (see leaves & hairs below). which support the leaves, flowers, and fruits. In ified branches non-woody plants (“herbs”), there is no trunk. I Clonal growth : Many plants have stems that Instead, these plants have soft, green stems that can creep on top (stolons) or under the ground support the leaves, flowers, and fruits. (rhizome) producing new “plantlets”, which are clones of the parent. Although common in I Transportation : Stems serve to transport the e.g materials needed in photosynthesis. Inside a herbaceous plants ( . strawberries, crabgrass), stem there are tissues called xylem and phloem. some trees also exhibit clonal growth. These Both are tubes that transport materials through trees are said to have “suckers” growing from e.g the plant: xylem water and sugars, respectively their base ( . crabapple, aspens). (see xylem & phloem below) . I Storage : Many stems store food, water, and what are leaves? waste products. An example of a storage stem is Many leaves are composed of three parts: the the white potato (Solanum tuberosum), which blade , the petiole , and stipules . The blade is could be called a tuber. Food and water storage the flat, wide, photosynthetic part of the leaf. in common in arid conditions. Plants cannot The petiole is the thin stalk that holds the blade easily get rid of harmful chemicals from the air and attaches the leaf to the stem. Stipules look and soil; therefore, they store these chemicals in like tiny leaves that are found at the base of the special cells. petiole; they are not always present. An oak I Photosynthesis : Almost all plants have stems leaf has a clear example of blade and petiole, that can photosynthesize. Some plants have but grass leaves have blades only. Both are stems that are always green, such as cacti and example of simple leaves, because the blade is palo verde. Other plants, such as oaks, just use entire and not split/sectioned into leaflets. A their young twigs and leaves for photosynthesis. leaf that is segmented into leaflets is called a compound leaf. I Protection : against large animals; these are called thorns. Many trees have thorns ( e.g . Discerning a leaf from a leaflet, and thus a sim - hawthorn, crabapple, honey locust). Note: Cacti ple from a compound leaf, can be challenging. and rose bushes do not have thorns, because The simplest way is to look at the intersection these are not modified branches (see leaves between the “stem” and the base of the “leaf”. and hairs below). If there is a bud at this location, then you are page 3 teacher resources: The Basics of Botany what are leaves? (continued) that wrap around other plants, fences, wire, etc. for support. observing the attachment of a leaf to a stem. I Protection : In many plants, leaves have been If the bud is missing, then you are looking at a modified to a sharp point to serve as protection: leaflet attached to a larger, compound leaf. spines. Many arid-adapted plants, such as cacti, All leaves have stomates, which are pores in have spines. the leaf, with guard cells that regulate the exchange of gases and water vapor with the what are flowers? environment. These stomates can be opened and closed to regulate the physiology of the Flowers are beautiful structures that are com - plant. Oaks, like many trees, have stomates posed of many parts. The flower forms in a only on the bottom of their leaves; grass leaves bud, and emerges on a short stalk or stem. have stomates on both sides. The end of this stem has four different parts: sepals, petals, stamens , and pistils. Each part Almost all people know what a leaf looks like, has a specific function (discussed below) that but contemporary leaves can range from will ultimately lead to fertilization of new microscopic (water weed: Wolffia) up to 83 seeds.