Transcript Unit 8
Intro to Horticulture Parts of the plant and their functions Environmental Science Functions of leaves . 1. Critical for photosynthesis (the process by which plants produce their food). 2. Aid in the process of transpiration which is necessary in order for plants to cool themselves. 3. Leaves can store some food which can later be transferred to other areas of the plant. 4. Sometimes, leaves can be used in asexual or vegetative propagation. External Leaf Structures Leaves are consist of petiole and blade – Blade is comprised of veins and a midrib The veins of the leaf form its structural framework . Internal Leaf Structures Epidermis – Cuticle Waxy substance covers the leaves and stems Waterproof layer that keeps water in plants Principal Tissues of the Leaf Epidermis (cont) – Stomata Openings in the epidermis mainly located on underside of leaves Exchange of gases •Guard Cells •Two cells located on each side of stomata •Open and closes stomata Chloroplast More in cells located in the center of the leaf The chloroplast contains chlorophyll which gives the plants the green color Manufactures food for the plant though Photosynthesis Beginning of the food chain for most living things Photosynthesis CARBON DIOXIDE + WATER + LIGHT ENERGY = GLUCOSE + OXYGEN Food manufactured by this process goes down to the roots thought the stem. It is either used by the plant or stored as a starch, sugar, or protein Respiration Plants respire 24 hours/day just as animals In this process they consume carbon dioxide and give off oxygen What is the purpose of the stems? Two main Functions – The movement of materials- water, minerals, food – Support the leaves and reproductive structures Can be used for food storage – Ex. Irish potato What are the types of stems? 1) Woody Stem: trees, shrubs, perennials 2) Grass Stem: hollow or filled 3) Herbaceous Stem: like wood but softer (clover, alfalfa) 4) Modified Stem: Types of Modified Stems Bulbs: (onion) Tubers: (potato) Stolons: above ground runner (strawberry) Rhizomes: below ground runners (field bindweed or creeping jenny) What is the Terminal Bud? Terminal bud tries to make plant grow taller or longer if we remove terminal bud, the plant will be shorter and thicker – Can you think of why we would want to do this?? – What kind of plants could we do this on?? Internal Stem Structure What does the Xylem Carry – Water and minerals travel up What about the Phloem – Manufactured food travels down the plant What does the Cambium do? – Separates the xylem and the phloem – Thin, green, actively growing tissue located between the bark and the wood of a plant Monocot vs. Dicot Dicot stem may continue to increase in diameter because the cambium builds new phloem cells on the outside and new xylem cells on the inside – Ex. Trees Monocot have vascular bundles which contain both xylem and phloem and no cambium – This would make it more limited in size Ex. corn Why should we care? The stems of some plants we use as food – Irish potato and asparagus Others are used in building materials – Lumber from the tree trunks Roots Roots function – Anchor the plant and hold it upright – Absorb water and minerals from the soil and conduct them to the stem – Store large quantities of plant food – Propagate or reproduce some plants Fibrous root vs. tap root Fibrous root system – Much easier to transplant – More spread out Tap root system – Longer fewer roots – End of root contains many root hairs Functions of Fruit: 1. Protect the seeds inside the ripened ovule (fruit). 2. Provide nutrients to the soil and to a newly germinated seedling. 3. Aid in the dissemination/spreading of seed by providing food for animals. Animals eat the fruit and seeds. After the fruit is digested, the seeds pass out in the animal’s feces at another location. 4. Some plants have dry, dehiscent fruits which split open to disseminate seeds. What is the purpose of seeds To continue the plant process There are two types – Monocots – dicots Monocot and dicot