All Plants… multicellular, eukaryotic, autotrophic
Angiosperms Monocots vs. Dicots named for the number of cotyledons present on the embryo of the plant + monocots - orchids, corn, lilies, grasses + dicotsdicots - roses, beans, sunflowers, oaks
Alternation of Generations Sporophyte (diploid) produces haploid spores via meiosis Gametophyte (haploid) produce haploid gametes via mitosis Fertilization joins two gametes to form a zygote
Plant Morphology Morphology (body form) - shoot system + stems, leaves, flowers - root system + taproot, lateral roots vascular tissues + transport materials between roots and shoots - xylem/phloem
Plant Anatomy Anatomy (internal structure) division of labor + cells differ in structure and function - parenchyma, collenchyma, sclerenchyma (below) Parenchyma St: “typical” plant cells Fu: perform most metabolic functions Collenchyma St: thick walls Fu: provide support but allow growth in young parts of plants Sclerenchyma St: hardened secondary walls (LIGNIN) Fu: specialized for support; dead
Plant cell types Xylem Phloem WATER-CONDUCTING CELLS OF THE XYLEM Vessel Tracheids Tracheids and vessels Vessel element Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Companion cell Sieve-tube member Sieve-tube members: longitudinal view Sieve plate Nucleus Cytoplasm Companion cell
Water- and Food-conducting Cells XylemXylem (water) dead at functional maturity PhloemPhloem (food) alive at functional maturity sieve-tube cells- arranged end to end with sieve plates & Companion cells
Plant Tissues Three Tissue Systems dermal tissue + epidermis (skin) - single layer of cells that covers entire body - waxy cuticle/root hairs vascular tissue + xylem and phloem - transport and support ground tissue + mostly parenchyma - filler tissue - photosynthesis, storage, support
Plant Growth Meristems embryonic tissues located at regions of growth - apical meristems (primary growth- length) + located at tips of roots and shoots - lateral meristems (secondary growth- girth)
Roots A root –Anchors the plant –Absorbs minerals and water –Stores organic nutrients –Taproots: vertical –Lateral roots: horizontal branches –Fibrous root system in monocots (e.g. grass) Figure 35.3
Buds An axillary bud –Forms a lateral shoot A terminal bud –Causes elongation of a young shoot Gardening tip: Removing the terminal bud stimulates growth of axillary buds (e.g. makes plants bushier)
The leaf Is the main photosynthetic organ of most vascular plants
Modified Leaves Tendrils Spines Storage leaves Bracts Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.
The Vascular Cambium and Secondary Vascular Tissue The vascular cambium –Is a cylinder of meristematic cells one cell thick –Develops from parenchyma cells
Secondary Growth As a tree or woody shrub ages –The older layers of secondary xylem, the heartwood, no longer transport water and minerals The outer layers, known as sapwood –Still transport materials through the xylem
Double Fertilization pollen grain lands on stigma + pollen tube grows toward ovule + 2 sperm discharged down the tube - egg and one of the sperm produce zygote - 2 polar nuclei and sperm cell produce endosperm + ovule becomes the seed coat + ovary becomes the fruit
Asexual Reproduction in Plants: Vegetative Propagation Budding and Grafting: smaller stems from one plant are attached to another plant Taking cuttings: pieces of one plant are used to grow another Stems can be modified: Runners: horizontal stems aboveground Rhizome: horizontal stems belowground Tuber: swollen underground stem
Plant Nutrition What does a plant need to survive?
Soil Bacteria and Nitrogen Availability Nitrogen-fixing bacteria convert atmospheric N 2 –plants absorb ammonium (NH 4 + ), nitrate (NO 3 - ) Atmosphere N2N2 Soil N2N2 N2N2 Nitrogen-fixing bacteria Organic material (humus) NH 3 (ammonia) NH 4 + (ammonium) H + (From soil) NO 3 – (nitrate) Nitrifying bacteria Denitrifying bacteria Root NH 4 + Soil Atmosphere Nitrate and nitrogenous organic compounds exported in xylem to shoot system Ammonifying bacteria
Nutritional Adaptations Symbiotic Relationships Mycorrhizae + symbiotic associations of fungi and roots - mutualistic relationship: fungus receives food from plant and plant receives increased surface area for root absorption
Minerals H2OH2O CO 2 O2O2 O2O2 H2OH2O Sugar Light A variety of physical processes –Are involved in the different types of transport Sugars are produced by photosynthesis in the leaves. 5 Sugars are transported via phloem to other parts of the plant. 6 Through stomata, leaves take in CO 2 and expel O 2. 4 Transpiration, the loss of water from leaves, pulls xylem sap upward. 3 Water and minerals are transported upward in the xylem. 2 Roots absorb water and minerals from the soil. 1 Roots exchange gases with the soil, taking in O 2 and discharging CO 2 in cellular respiration 7
Water and minerals ascend from roots to shoots through the xylem Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves The transpired water must be replaced by water transported up from the roots
Control of Transpiration Water enters guard cells and causes cells to swell, opening stomata. Water leaves guard cell and they shrink, closing stomata
Translocation Is the transport of organic nutrients in the plant Phloem sap Is an aqueous solution that is mostly sucrose Travels from a sugar source to a sugar sink Translocation through Phloem
A sugar source Is a plant organ that is a net producer of sugar, such as mature leaves A sugar sink Is an organ that is a net consumer or storer of sugar, such as a tuber or bulb Sugar Source & Sink
HOW DO PLANTS RESPOND TO THE ENVIRONMENT? Write down as many ways you can think of in your lab notebook.
Tropisms Growth toward or away from a stimulus Gravitropism (Gravity) Phototropism (Light) Thigmotropism (Touch)
Plant hormones help coordinate growth, development, and responses to stimuli Hormones –Are chemical signals that coordinate the different parts of an organism
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