CH28/30 Plant Structure Growth and Angiosperm Reproduction (Angiosperm…
CH28/30 Plant Structure Growth and Angiosperm Reproduction
3 Plant Organs Roots Shoots & Leaves
Roots- Anchors a vascular plant in the soil, absorbs minerals and water and typically stores carbohydrates.
Stem- Organ to which leaves are attached, Elongates and orient the shoot to have optimal levels of photosynthesis for the leaves
Leaf- Main photosynthetic organ, -Photosynthesis, Gas exchange, heat dissipation , defense against pathogens and herbivores
Mesophyll-Contains cells specialized for photosynthesis
Stomata-Allows gas exchange (Oxy/Carb Diox.) between env. air and photosynthetic cells in leafs
Guard cells-Regulate opening & closing of stomata (Which influences water loss
Vascular tissue- (Xylem/Phloem) transports nutrients & Photosynthetic materials
Three Tissue Systems in Plants (Dermal tissue, Vascular tissue, Ground Tissue)
Dermal Tissue- Plant's outer protective covering, Defends against pathogens & potential physical damages
Non-Woody plants- Have an epidermis (which are tightly packaged cells) & Cuticle (waxy coating on epidermal surface to prevent water loss)
Woody Plants- Periderm as apposed to epidermis in older regions of stems & roots
Vascular tissue- Facilitates transport materials through plant, Mechanical support
Xylem-transports water & dissolved minerals up from roots into shoots
Phloem-Transports Carbohydrates/Sugars to roots & sites of growth
Stele-Vascular tissue of a root or stem
Vascular cylinder-In root
Vascular bundles- In stems & leaves
Ground Tissue System- Tissues that are not vascular or Dermal (Contains cells that function in photosynthesis,short distance transport, storage or support
Pith-Internal tissue to vascular tissue
Cortex-External tissue to Vascular tissue
Plant Growth (Primary V. Secondary Growth)
Primary Growth- Occurs at apical meristems in roots & Auxillary buds of shoots in Both non-woody & woody plants (does produce almost all non woody plants) Can expirence apical dominance where an active apical bud inhibits growth from nearby axillary buds causing the plant to grow laterally vs vertically
Secondary Growth- Occurs at Lateral Meristems (Vascular Cambium + Cork Cambium) Grows in thickness in parts of stems & roots that no longer grow in length (ONLY OCCUR IN WOODY PLANTS!)
Pollination- Act of placing pollen on the stigma of a carpel Types of pollinators include bees,moths/butterflies,flies, bats & birds (Self fertilization- Angiosperms can combine their own pollen + Ovule to form zygote)
Life Cycle of an angiosperm
(Male gametophyte formation) Begins with a diploid (2n) flower on the mature sporophyte plant. Microsporocytes develop and undergo meiosis to produce haploid (n) microspores. Each microspore undergoes one mitotic division to produce a generative cell and a tube cell. Together they make an immature microgametophyte, or pollen grain.The generative cell completes a second mitotic division to produce two sperm nuclei.
(Female gametophyte formation)- Inside the ovule a single megasporocyte develops, undergoes meiosis, and produces four haploid (n) megaspores, Three of these die off, while the fourth undergoes three mitotic divisions to produce an eight-nucleate embryo sac, or mature megagametophyte. .
Pollination-the pollen grain germinates on the stigma, a pollen tube grows down the style and into the ovary through the micropyle. One sperm nucleus fuses with the egg to create a diploid (2n) zygote, while the other sperm nucleus fuses with the two polar nuclei to produce the triploid endosperm. The embryo develops inside the embryo sac, integuments of the ovule form a protective seed coat around it that provides protection and nutrients.
Last Steps-The seed is then shed from the fruit and the development of the embryo is temporarily halted until the proper conditions are established. Once the proper conditions are established seed germination takes place and the embryo grows into a mature diploid (2n) sporophyte, which produces flowers
Asexual Rep.in Angiospems
No need for pollinator
Offspring have desirable genomes (compared to only half its alleles) – can also be con!
Generally stronger progeny (skips weak seedling stage)
Less “costly” for parent’s resources (compared to making a ton of seeds)
Sexual Reproduction in Angiosperms
paves the way to unique individuals
removes bad genes from the population