plant organ: leaves

• A leaf blade is the broad, flat part of a leaf.
• A petiole is the part of a leaf that attaches the blade to the stem.
• Leaf morphology can be simple, pinnately compound, or palmately compound.
• Leaf arrangement can be alternate, opposite, or whorled.
• Sucrose is converted to starch (osmotically inactive).
• Water leaves by osmosis, guard cells lose their turgidity, pore closes.
• Increased turgidity changes the shape of guard cells, causing stoma to open.
• Water enters guard cells from surrounding epidermal cells by osmosis.
• As evening approaches, sucrose concentration in guard cells declines.
• Venation patterns include parallel, pinnately netted, and palmately netted.
• Photosynthesis is the biological process that includes the capture of light energy and its transformation into chemical energy of organic molecules such as glucose, which are manufactured from carbon dioxide and water.
• The major tissues of a leaf are the epidermis, mesophyll, xylem, and phloem.
• The epidermis allows light to penetrate into the mesophyll, where photosynthesis occurs.
• A cuticle is a waxy covering over the epidermis of aerial parts (leaves and stems) of a plant, enabling the plant to survive in the dry conditions of a terrestrial environment.
• Trichomes are specialized epidermal cells located on aerial parts of plants and are associated with a wide array of biological processes, protecting plants from adverse conditions including UV light and herbivore attack and are also an important source of a number of phytochemicals.
• A stoma is a small pore in the epidermis of a stem or leaf, permitting gas exchange for photosynthesis and transpiration, and is flanked by guard cells.
• Stomata typically open during the day, when photosynthesis takes place, and close at night.
• Bract is a modified leaf associated with a flower or inflorescence but not part of the flower itself.
• Bulb is a rounded, fleshy, underground bud that consists of a short stem with fleshy leaves, specialized for storage.
• As autumn approaches, plant reabsorbs sugar.
• A protective layer of cork cells develops on the stem side of the abscission zone.
• Red water-soluble pigments are synthesized and stored in vacuoles of leaf cells in some species.
• Chlorophyll is broken down.
• Enzymes dissolve the middle lamella in the abscission zone, which is the “cement” that holds the primary cell walls of adjacent cells together.
• Carnivorous plants are a type of plant that captures and digests insects.
• Bud scale is a modified leaf that covers and protects the delicate meristematic tissue of winter buds.
• Essential minerals are transported out of leaves.
• After the leaf detaches, the protective layer of cork seals off the area, forming a leaf scar.
• Modified leaves and their functions include bud scale, spine, bract, tendril, and bulb.
• Tendril is a leaf or stem modified for holding on or attaching to objects, which supports weak stems.
• Spine is a leaf modified for protection, such as a cactus spine.
• The area where the leaf petiole detaches from the stem is composed primarily of thin-walled parenchyma cells.
• Ions accumulate in vacuoles of guard cells, causing the solute concentration to become greater than that of surrounding cells.
• Photosynthetic ground tissue in the interior of a leaf is known as mesophyll.
• Eudicot leaves are usually broad and have netted venation.
• Two guard cells form a pore (stoma)
• Bulliform cells are large, thin-walled cells on the upper epidermises of leaves of certain monocots (grasses), located on both sides of the midvein, and may help leaf roll or fold inward during drought.
• Blue light activates proton pumps in guard-cell plasma membrane.
• Mesophyll contains air spaces for rapid diffusion of carbon dioxide and water into, and oxygen out of, mesophyll cells.
• Guard cells of eudicots and many monocots are bean-shaped.