BIO 123 1st Edition Lecture 2 Outline of Last Lecture I. The Plant Bodya. Root and Shoot Systemb. The 3 Tissue SystemsII. Growth in Plantsa. Growth specific regionsb. Primary vs. Secondary GrowthOutline of Lecture 2I. Parts of a Leafa. Leaf Anatomyb. Leaf FormsII. Adaptations for PhotosynthesisIII. TranspirationIV. Leaf AbscissionV. StemsLecture 2 I. Parts of a LeafLeaves- Broad, Flat blade - Maximize surface area- Stalk like petiole - Some have stipules- Monocot Leaves: Parallel- Eudicot Leaves: Netted, branchedLeaf Anatomy Dermal Tissue:o Guard Cells- There are 2 guard cells on every stoma (small pore on epidermis, that permits gas exchange for photosynthesis)- They are specialized epidermal cellsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- They regulate the opening and closing of the poreo Epidermis - Coated by a waxy cuticle- Helps plants survive life on land / dry conditions Upper Epidermis  Lower Epidermiso Epidermal Cells Ground Tissue:o Bundle Sheath Cell o Mesophyll- Is photosynthetic parenchyma cells- Responsible for chlorophyll Palisade Mesophyll- One or more layers of elongated parenchyma cells (specialized for photosynthesis) - Located on the upper part of the leaf- Functions primarily for photosynthesis Spongy Mesophyll- Is below the palisade mesophyll- Made of parenchyma cells- Parenchyma cells are loosely arranged, with air spaces- This allows carbon dioxide and oxygen to circulate around and up into the palisade region - Air spaces are large near stomata because this is where carbon dioxide is taken inside the plant from the outside air, and thus oxygen is released from the plant into the air. - Carbon dioxide - in- Oxygen - out  Vascular Tissue:o VeinsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Subdivide repeatedly - Branch out through mesophyll- Veins bring xylem and phloem closer with photosynthetic tissue- Obtains water and minerals from the xylem and loads its sugars and other organic material into the phloem for transport into other parts of the plant. o Xylem- Conducts water and essential minerals to leafo Phloem- Conducts sugars produced by photosynthesis to the rest of the plant Leaf Form Simpleo Undivided blade Pinnately Compoundo Leaf vein is subdividedo Leaflets are arranged alongthe main or mid-vein Palmately Compoundo Leaf vein is subdividedo Leaflets diverge from the end of the petiole (like the fingers off the palm of the hand). Leaf Arrangement Alternateo Single leaves are attached at thenodesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o They alternate in direction along the stem Oppositeo They are two structures one on each opposite side of the stemo They are attached in pairs on each node Whorledo Here three or more leaves attach at each node on the stemVenation Patterns Parallelo Veins arranged axiallyo Veins do not intersect Pinnately Nettedo 2 sets of veinso Paired oppositely  Palmately Nettedo Several primary veinso Diverging from a point Key Concept: Monocot Leaves have parallel venation + Eudicot Leaves have netted venation II. Adaptations for Photosynthesis  Most leaves have broad, flattened bladeo Efficient in collecting sun’s radiant energyo More Sun = Water LossThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Plants keep their Stomata open during dayo For gas exchange needed in photosynthesis Close Stomata at nighto To conserve water when photosynthesis is not occurring- (Exception for in CAM Plants, which keep their stomata open at, because they live in arid environments)  Transparent Epidermis o Allows light to penetrate into the middle of the leaf (where photosynthesis occurs) Air Space in Mesophyll Tissueo Permits rapid diffusion of CO2 and water into and oxygen out of mesophyll cellsClicker Question:Leaves are important to plants for obtaining water = TrueIII. Transpiration  The loss of water vapor from aerial parts of the plant - evaporation - Occurs primarily through stomata  Is beneficial and harmful to plants Carbon Dioxide is needed for photosynthesis Plant needs to conserve water Speed of Transpirationo Is affected by environmental factors such as: temperature, wind, and These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.relative humidityIV. Leaf Abscission  Loss of leaves Occurs when winter approaches in temperate climates Occurs at the beginning of dry periods in tropical climates with wet and dry seasons It is a complex process Physiological and anatomical changes occur prior to leaf fallKey Concepts: Some leaves are modified for special functions in addition to photosynthesis andTranspiration. V. Stems Consists of nodes and internodeso Nodeso Area on a stem where leaf is attachedo Internodeso Region of stem between two nodes Monocot Stem vs. Eudicot Stemo Monocot stem: vascular bundles scattered throughout the ground tissueo Eudicot stem: vascular bundles are arranged in a ring pattern Vascular Cambiumo A cylinder of meristematic cellso Appears as a ring in tree stem cross sectiono Responsible for the production of secondary vascular tissue o Produces secondary xylem (wood) and secondary phloem (inner bark) during secondary growtho Usually located outside the pith and primary xylemo These cells divide, increasing the cambium’s circumferenceThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Cork Cambiumo A cylinder of dividing cells located in the outer cortex of the stems and in the pericycle in rootso Produces Periderm- Periderm is a thick protective covering- Periderm consists of cork cambium and cork cells  Cork cellso Replaces epidermis in a woody stem. Helps protect against water loss Cork parenchymao Primarily for storage in a woody stemMB: Plants must always compromise between maximizing photosynthesis and minimizingwater loss