Presentation on theme: "Plant Structure and Growth Chapter 35. Plants with vascular tissue have 3 structures - roots, shoots, leaves. 2 groups of angiosperms, monocots and dicots,"— Presentation transcript:
Plant Structure and Growth Chapter 35
Plants with vascular tissue have 3 structures - roots, shoots, leaves. 2 groups of angiosperms, monocots and dicots, differ in structures.
Structures divided into 2 systems: root system (below ground), shoot system (above ground). Systems rely on one another; roots - no chloroplasts - need shoots to photosynthesize.
Monocots (grasses) - fibrous root systems (mat-like). Dicots (flowers) - taproot system with one large root. Most absorption of water and minerals occurs near root tips with root hairs - increase surface area.
Some plants - adventitious roots - arise aboveground from stems or even from leaves. In corn - help to keep plant upright.
Stems have nodes - leaves attached, internodes - spaces between nodes. Where leaves meet stems - axillary buds - vegetative branch could form. Terminal bud - growth of young shoot concentrated. If terminal bud present, growth happens vertically - apical dominance.
Modified shoots 1 Stolons - “runners” of strawberry plants - grow on surface so that parent plant can asexually reproduce in large numbers.
2 Rhizomes (ginger) - horizontal stems - grow underground. 3 Tubers (potatoes) - swollen ends of rhizomes specialized for food storage. 4 Bulbs (onions) - vertical, underground shoots consisting mostly of swollen bases of leaves that store food.
Leaves consist of flattened blade and stalk (petiole) Some leaves evolved other purposes (spines of cacti for defense, leaves modified for water storage, brightly colored leaves that attract pollinators)
Each organ of plant - 3 tissue systems: dermal, vascular, ground. Dermal system consists of epidermis (covers, protects) Epidermis of leaves, most stems secretes waxy coating (cuticle) - helps parts of plant retain water.
Vascular tissue involved in transport of materials between roots and shoots. 1 Xylem – tissue that conducts water and minerals from roots to rest of plant. 2 Phloem transport nutrients, especially carbohydrates produced in leaves down stem.
2 types of xylem cells: vessel elements, tracheids. Dead at maturity - help to thicken walls to promote water flow. Tracheids - long, thin cells with tapered ends. Vessel elements - wider, shorter, thinner walled, less tapered than tracheids.
2 types of phloem cells - companion cells, sieve tube members. Sieve tube members - tubes that material moves through. Companion cells assist sieve tube members.
Ground tissue - tissue neither dermal nor vascular. Dicot stems, ground tissue divided into pith, internal to vascular tissue, and cortex, external to vascular tissue.
3 different types of plant cells: parenchyma, collenchyma, and sclerenchyma. Parenchyma cells - primary walls that are relatively thin and flexible; typical plant cells; ex. sieve-tube members.
Collenchyma cells -thicker primary walls than parenchyma cells - used for support in growing plants. Sclerenchyma cells also function as supporting elements of plant.
Growth of tissues in plants Annual plants complete life cycle in single year or less. Biennial plants - 2 years. Plants that live many years, including trees, shrubs, and some grasses, are perennials.
Growth in plants due to embryonic cells (meristems) Elongate and differentiate into cell types depending on tissue of plant.
Apical meristems found at tips of roots, stems - allow for growth in length - only happens at tips. Primary growth occurs lengthwise, secondary growth - widthwise. Lateral meristems responsible for secondary growth.
Root tip protected by root cap to protect meristem.
Axillary buds have potential to form branches of shoot system. Vascular tissue runs length of stem in strands (in vascular bundles)
Leaf epidermis composed of cells tightly locked together. Full of stomata - controlled by guard cells around that can open and close opening.
Spongy layer of cells inside leaf has chloroplasts with air spaces around cells. Palisade layer in leaf has densely packed cells spread over large surface area.
Lateral meristems 2 cambiums responsible for secondary growth. Vascular cambium - meristem to produce secondary xylem and secondary phloem. Cork cambium - meristem for tough, thick covering for stems and roots - replaces the epidermis.
As secondary growth continues over years, layer upon layer of secondary xylem accumulates, producing wood. Actually dead cells. Growth in areas like Maine occur in cycles - dormancy then growth - produce growth rings.
Bark - all tissues external to vascular cambium (secondary phloem, cork cambium, cork) 2 types of secondary phloem: heartwood and sapwood. Heartwood (hardwood) no longer conducts water; sapwood (softwood) functions in transport of water and minerals.