Presentation on theme: "P LANTS S TRUCTURE AND G ROWTH. F RUIT an organ that contains seeds, protecting these as they develop and often aiding in their dispersal. derived from."— Presentation transcript:
F RUIT an organ that contains seeds, protecting these as they develop and often aiding in their dispersal. derived from ovaries, and other flower parts. Ovary walls thicken to form pericarp Can be composed of up to 3 layers Exocarp Mesocarp Endocarp
T YPES OF F RUIT Simple fruits – form from a simple ovary of a single carpel, or from a compound ovary of several fused carpels Dry fruits Achenes – close fitting pericarp around single seed Sunflowers Grains – pericarp is fused to a single seed Wheat, corn Nuts - thick woody pericarp fused to a single seed Walnuts, hazelnuts, acorns Legumes - Pod that splits along two opposite sides Beans, peas, peanuts
T YPES OF F RUIT CONT ’ D Simple fruits – cont’d Fleshy Fruits – mesocarp forms flesh Drupes – 1 or 2 seeds, stony endocarp Plum, peach Berries – 1 to many seeds, no stony endocarp Tomatoes,, grapes, all citrus
T YPES OF F RUIT CONT ’ D Compound/Aggregate Fruits Develop from several individual ovaries of one flower Raspberries Strawberries...the inside is not actually fruit, but flesh formed from the receptacle Multiple fruits Formed from the fusion of many carpels belonging to separate flowers pineapple
S EEDS AND Y OUNG S HOOTS Germination occurs when conditions are favorable Need: water, warmth, and oxygen Many seeds remain dormant until certain conditions are met Inhibitors prevent germination, stimulators trigger it High moisture levels, period of cold weather, fire etc...
S EEDS AND Y OUNG S HOOTS Initial leaves to appear are the cotyledons In dicots the cotyledons provide initial nutrition in monocots endosperm fills this role First root to appear is the radical.
E PIDERMAL T ISSUE Surrounds entire body of herbaceous and young woody plants “Bark” develops after first year of growth Bark is only a small portion of the new outer layer called periderm Closely packed cells, designed to protect, and minimize water loss.
E PIDERMAL T ISSUE – CONT ` D Specialized epidermal cells: Root Hairs – Long projections from epidermal cells to increase surface area Trichomes – hairs on stems, leaves and reproductive organs to protect against moisture loss Guard Cells – surround microscopic holes on underside of leaves, able to open and close for gas exchange. F IG. 9.4 A
G ROUND T ISSUE Forms the bulk of the plant 3 main cell types Parenchyma Most abundant, look like ‘typical’ plant cell Least specialized, often contain plastids that store products of photosynthesis.
G ROUND T ISSUE CONT ’ D Collenchyma Thickened cell wall, provide flexible support Strands in celery Sclerenchyma Have thick secondary cell walls, mostly non-living, provide support and structure Fibres – hemp, flax Sclerids – stones in peaches, grittyness of pears.
V ASCULAR T ISSUE Located in Vascular cylindar in roots Vascular bundles in stems Veins in leaves Two primary tissues Xylem and Phloem
V ASCULAR T ISSUE Xylem Water and minerals from roots to leaves Two cell types, both non-living at maturity Tracheids, Vessel elements F IG 9.6
V ASCULAR T ISSUE Phloem Sugar and other organic compounds, including - hormones, usually from leaves to roots Two cell types Sieve tube members – have holes between to form continuous tube, no nucleus Companion cells have nucleus, controls and maintains life of both cells. F IG 9.7
L EAVES Photosynthetic organs of plants Structure generally a flattened blade and a petiole that attaches to stem Simple leaves – single blade Compound leaves – many blades on one petiole Adaptations Shade plants – broader leaves, darker in colour Xerophytes – no moisture, small needle-like leaves Tendrils to attach to objects Catch insects
L EAF S TRUCTURE Cuticle (upper and lower) Waxy layer prevents moisture loss Epidermis (upper and lower) Outer layer of cells, provides structural support, generally no chloroplasts
L EAF S TRUCTURE CONT ’ D Pallisade Mesophyll Brick like cells, stacked on end Primary site of photosynthesis Spongy Mesophyll Irregular cells, Loosely packed, lots of air space Promotes gas exchange Veins are held within this layer Veins Vascular tissue surrounded by bundle sheath cells
L EAF S TRUCTURE CONT ’ D Stomata lower epidermis, regulates gas exchange and water levels Opening surrounded on each side by two large guard cells. Water levels control opening and closing absorb water swell stomata opens. lose water relax stomata close During the heat of the day, water levels decrease, stoma stay closed Helps to decrease water loss At night, water levels are able to rise, stoma open allowing leaves to release excess water, exchange Carbon Dioxide and Oxygen.