PLANTS Chapter 9: An introduction Basic Needs Energy Photosynthesis, heterotrophs
Nutrients Water Gas exchange Protection from herbivores and disease Reproduction PLANTS: Anatomy, Growth and Functions
Plants : Kingdom Plantae Cells are eukaryotic Cell walls contain cellulose Synthesize carbohydrates through process photosynthesis The three hundred thousand to five hundred thousand species identified display such diversity that no single species can be cited as a typical example of the kingdom
An Brief Intro to Plants All living organisms require chemical energy (ATP) to run the various chemical reactions that sustain life. In the process of cellular respiration, organisms convert simple sugars (i.e. glucose) into that chemical energy. Animals such as ourselves obtain sugars from the food we eat. But how do plants obtain the sugars
required for cellular respiration to sustain life? Photosynthesis! The chemical process in which plants make sugar using light energy, water and carbon dioxide, making oxygen as a side product. The sugar made during photosynthesis can then be used for cellular respiration.
Equation for Photosynthesis: From the atmosphere From the Sun 6 CO2 + 6 H2O + Light Energy C6H12O6 + 6O2 From the surrounding
environment A variety of simple sugars may be formed, though glucose (C6H12O6) is one of the most common. If any of the reactants are lacking or are limiting, photosynthesis may not occur and the plant may die. Phylogeny Bryophyte- nonvascular mosses
Lycophytes/ pterophytesvascular non seeding ferns Gymnospermsseeds in cone e.g. conifers Angiosperms- seeds in flowers Amazing Diversity.. After millions of years of evolution and development, an enormous number of different plant variations have
been created. Plants have unusual lives as they are immobile, they cannot move independently and are therefore limited to the environment around them To cope with their immobility, plants have many adaptations to survive a variety of environmental conditions. Ex. the pitcher plant lives in low nitrogen soil and has evolved a unique way of getting its food Pitcher Plants
(Nepenthes) Nepenthes is a genus of carnivorous plant The colorful rim functions as a lure to insects. A syrupy liquid in attracts, and drowns, and digests potential prey.
Waxy walls prevent escape of insects that have fallen prey Sensitive Plant (Mimosa pudica) Touch me nots Leaflets fold in and droop when they are touched. This is caused by a drop of pressure in certain
cells, and leads to a very cool effect. The leaves also react to heat and light which causes the plant to fold up every evening. http://www.youtube.com/wa tch?v=Zq3UuHlPLQU Venus Flytrap (Dionaea muscipula)
most well-known carnivorous plant There are small trigger hairs on the leaves which causes them to fold together when they are touched. The leaves close in less than a second, and the teeth-like spikes on the edge keep larger insects from escaping. http://www.youtube.com/watch?v=9sggQQuBU40 Resurrection Fern (Polypodium polypodioides) incredible ability to withstand drought. During dry spells, the plant curls up into a ball, turns
brown, and appears to be dead. If it comes in contact with water, it uncurls and comes back to life It has been estimated that it can survive for 100 years without water. http://www.youtube.com/watch?v=jdB_pmzhhbE Rafflesia arnoldii Found in Sumatra considered to be the largest flower in the world. It can grow to be up to one meter in diameter,
and weigh as much as 25 lbs. Despite its size, it is incredibly difficult to find because it takes 9-21 months for plant to develop, and the flower lasts for a maximum of five days. http://www.youtube.com/w atch?feature=endscreen&
v=ZgHhDsJSXOI&NR=1 Structure of vascular plants Structure of vascular.. Underground- root system Above ground shoot system 3 main non-reproductive Leaves, stems, roots These are made up of; Dermal tissue
Vascular tissue Ground tissue Meristematic tissue(meristem) actively dividing undifferentiated cells. Found where growth occurs. Become specialized. Periderm= bark LEAVES
Characteristics of leaves have evolved gradually in order to maximize the efficiency with which they : Photosynthesize Reduce water loss Avoid being eaten Survive extreme conditions ie. Diversity of species has resulted in survival of some species in a location
but not for others. Leaf Adaptations Plants with broad leaves survive in shaded areas, but will die in open sunny fields Conifers, with their thin , long needles have a thick, waxy cuticle to avoid water loss and survive short growing season by keeping their leaves through winter Leaves with thick layers of water storage tissue have an extra thick waxy cuticle to prevent water
loss and survive low precipitation/salty soil (cacti) Leaves that are tough, hairy, prickly and bitter are avoided by herbivores Plants with toxic chemicals in tissues control herbivore populations (nicotine in tobacco leaves is an insecticide LEAF STRUCTURE Site of photosynthesis Leaves are positioned along stem at points called nodes, the
spaces between nodes are called internode Leaf is connected to plant by the petiole Parallel venation is characteristic of monocots Net venation is characteristic of dicots a single, undivided blade is called a simple leaf A blade divided into two or more
leaflets is called a compound leaf Leaves 3-D Cross-Section of a Leaf Protects the leaf from excessive absorption of light and evaporation of water A transparent colourless layer that allows light to
pass through to the mesophyll cells Where most of the photosynthesis takes place (abundant in chloroplasts). Photosynthetic epidermal cells that create microscopic
openings called stomata. Regulates the exchange of gases in the atmosphere A system of vessels that transport water, minerals, and carbohydrates
within the plant. Internal leaf structure Epidermal cells- outer layer just under cuticle tightly packed. Prevents water loss and prevents infection from bacteria and fungi. Do not perform photosynthesis, but are transparent to let light through. Mesophyll- middle leaf. Contain majority of chlorophyll. Two types; Palisade mesophyll- elongated and tightly packed. Contain many chlorophyll.
Spongy mesophyll - mesophyll cells are loosely packed with large air spaces, which allow for gas exchange between the mesophyll cells and the atmosphere through stomata Control of Gas exchange Stoma- A stoma (plural: stomata) is an opening in the epidermis of a leaf, through which gases pass in and out. Guard cells- two kidney shaped cells control the opening and closing of a stoma.
In terrestrial plants, most of the stomata are in the lower epidermal layer, below the spongy mesophyll. Stomata Stomata Each stoma is surrounded by a pair of guard cells that control the control the size of a stoma by changing their shape in response to
water movement by osmosis in the cells. When water moves into guard cells, the cells become turgid (swollen) and the stoma opens. When water move out of the guard cells, the guard cells become flaccid CO 2
O 2 Cell Turgor Pressure the pressure inside the cell that is exerted on the cell wall by the plasma membrane created by water entering the cell via osmosis Stomata Opening In general, stomata are open in the
daytime and closed at night. When the Sun comes out in the morning, it activates receptors in the guard cell membranes, stimulating proton pumps that pump H+ out of the guard cells. K+ move into the cells, followed by water (via osmosis) Stomata Closing Hormone absicis acid (ABA) causes the
stomata to close. Also, changes the particles in the guard cells of the stomata will cause the guard cells to lose water and become flaccid, closing the stomata. H+ are pumped out of guard cells K+ diffuses into guard cells H2O diffuse into cells by osmosis Guard cells swell and open CO2 enters stoma
Stems Connect vascular tissue in leaves to vascular tissue in roots Transports water and dissolved nutrients Raise and support the leaves and reproductive organs Raising leaves maximizes exposure to sunlight Raising reproductive organs places them in
the ideal position for pollination Transpiration Plant leaves are the primary organ of photosynthesis Gas exchange happens through the stomata Some water vapour can be lost through stomata also Water loss through stoma is called transpiration
Guard cells control the aperture of the stoma and thus limit water loss STEMS Adaptations: Stem tubers are modified for food storage which can form from roots (e.g. potatoes) Tendrils will attach the plant to something. When the tendril touches something, the other side will grow faster to make it wrap around an object (e.g. sweet pea)
Storage- modified stems in cacti can store large volumes of water Stem Structure STEM TYPES: 1. Herbacious : thin, soft, green, short-lived, photosynthetic, and contain little or no wood. Less than 1m tall. Stems of annual plants surviving only one year. 2. Woody: describes stems of perrennial plants. As
more vascular tissues is created, they increase in diameter. Dead xylem cells create the hard tissue called wood. Bark consists of all tissue from the vascular cambium outward; Heartwood is darker, dead, older, xylem plugged with oils, and; Sapwood is lighter, live, younger xylem transporting water and other dissolved materials. ROOTS Absorb water and minerals from the soil
Physically support and anchor plants Store carbohydrates Produce compounds (e.g. hormones) A primary root develops from seed and branching from it is the secondary root (lateral root) Storage roots (e.g. carrots) have been modified to store water or food
Roots Root hairs increase the surface area over which water and mineral ions may be absorbed. The Root cap is important in protecting the apical meristem during primary growth of the root through the soil. TAPROOT
VS FIBROUS ROOT TAPROOTS Young root increases in diameter, grows downward, and develops small lateral roots. ie. Carrots, beets, dandelions, oak trees
FIBROUS ROOTS Primary root is shortlived and is replaced by Adventitious roots. Adventitious roots and their lateral roots make up the fibrous root system. ie. Grasses, and other monocots
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