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Plant Growth Growth in Animals Animals grow throughout the whole organism many regions & tissues at different rates Growth in Plants Specific regions of growth: _____________ stem cells: perpetually embryonic tissue regenerate new cells ___________________ growth in length primary growth ___________________ growth in length primary growth ___________________ growth in girth (width) secondary growth Apical meristems shoot shoot Root structure & growth protecting the meristem Shoot growth Apical bud & primary growth of shoot region of stem growth __________________ “waiting in the wings” protecting the meristem Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium Vascular tissue Primary xylem Growth in woody plants Primary phloem Woody plants grow in Epidermis height from tip Lateral meristems primary growth ______________________ Woody plants grow in diameter from sides Primary phloem secondary growth ______________________ Secondary phloem Secondary Primary xylem xylem _____________________ makes 2° phloem & 2° xylem _____________________ makes bark Annual growth layers Bark Secondary growth Secondary growth growth in diameter thickens & strengthens older part of tree ____________________________________ growing ring around tree ____________________________________ growing ring around tree Vascular cambium Why are early & late growth different? Phloem produced to the outside Xylem produced to the inside bark cork cambium phloem phloem vascular cambium late early last year’s xylem cork cambium Woody stem How old is this tree? vascular cambium late early 3 2 1 xylem phloem bark Tree trunk anatomy tree girdling What does girdling do to a tree? Aaaargh! Murderer! Arborcide! Tree trunk anatomy tree girdling What does girdling do to a tree? Aaaargh! Murderer! Arborcide! Where will the carving be in 50 years? Plant hormones __________________ __________________ __________________ __________________ and more… Auxin (IAA) Effects controls cell division & differentiation __________________ growth towards light asymmetrical distribution of auxin cells on darker side elongate faster than cells on brighter side __________________ Gibberellins Family of hormones over 100 different gibberellins identified Effects stem elongation ____________________ ____________________ plump grapes in grocery stores have been treated with gibberellin hormones while on the vine Abscisic acid (ABA) Effects ____________________ ____________________ high concentrations of abscisic acid germination only after ABA is inactivated or leeched out survival value: seed will germinate only under optimal conditions light, temperature, moisture Ethylene Hormone gas released by plant cells Effects ____________________ ____________________ like in Autumn apoptosis One bad apple spoils the whole bunch… Fruit ripening Adaptation hard, tart fruit protects developing seed from herbivores ripe, sweet, soft fruit attracts animals to disperse seed Mechanism triggers ripening process breakdown of cell wall softening conversion of starch to sugar sweetening positive feedback system ethylene triggers ripening ripening stimulates more ethylene production clusters of fruit ripen together Apoptosis in plants Many events in plants involve apoptosis response to hormones ethylene auxin death of annual plant after flowering senescence differentiation of xylem vessels loss of cytoplasm shedding of autumn leaves What is the evolutionary advantage of loss of leaves in autumn? Don’t take this lying down… Ask Questions!! 2007-2008 Apical meristems shoot shoot Root structure & growth protecting the meristem Shoot growth Apical bud & primary growth of shoot region of stem growth __________________ “waiting in the wings” protecting the meristem Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium Vascular tissue Primary xylem Growth in woody plants Primary phloem Woody plants grow in Epidermis height from tip Lateral meristems primary growth ______________________ Woody plants grow in diameter from sides Primary phloem secondary growth ______________________ Secondary phloem Secondary Primary xylem xylem _____________________ makes 2° phloem & 2° xylem _____________________ makes bark Annual growth layers Bark Vascular cambium Why are early & late growth different? Phloem produced to the outside Xylem produced to the inside bark cork cambium phloem phloem vascular cambium late early last year’s xylem cork cambium Woody stem How old is this tree? vascular cambium late early 3 2 1 xylem phloem bark Basic plant anatomy 1 Leaves Function of leaves photosynthesis energy production CHO production gas exchange transpiration simple vs. compound Parenchyma Parenchyma cells are unspecialized, thin, flexible & carry out many metabolic functions all other cell types in plants develop from parenchyma Collenchyma Collenchyma cells have thicker primary walls & provide support help support without restraining growth remain alive in maturity the strings in celery stalks are collenchyma Sclerenchyma Thick, rigid cell wall lignin (wood) cannot elongate mostly dead at maturity Cells for support xylem vessels xylem tracheids fibers rope fibers sclereids nutshells seed coats grittiness in pears vessel elements Xylem vessel element Vascular tissue move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H2O transpirational pull dead cells Aaaah… Structure–Function again! tracheids Phloem: food-conducting cells carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells Phloem: food-conducting cells sieve tube elements & companion cells Vascular tissue in stems dicot trees & shrubs collect annual rings monocot grasses & lilies Vascular tissue in roots: dicot phloem xylem Vascular tissue in roots: monocot xylem phloem Flower Modified shoot with 4 rings of modified leaves sepals Stamen petals stamens Stigma Style Ovary Anther Carpel Filament male carpel female sepals petals stamens Petal Ovule Sepal adaptations through mutations carpel What is a Cotyledon? Cotyledon: seed leaf in the embryo of an angiosperm that hold food for the developing plant May form a leaf after germination