Chapter 6 BOT 3015 L Biology of Flowering
Chapter 6 BOT 3015 L Biology of Flowering Plants Anatomy Seedlings, Meristems, Stems, and Roots Presentation created by Danielle Sherdan All photos from Raven et al. Biology of Plants except when otherwise noted
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
Life cycles From Outlaw’s lecture series
Floral structure Angiosperm life cycle Gametophytes Today From Outlaw’s lecture series
Monocot seed development typical monocot (maize) seed with ovary wall (pericarp) Monocots have one cotyledon (scutellum in grasses) that matures during germination Source of nutrition for seed germination: endosperm (compare to dicot) Maize fruit and seed
Dicot seed development immature dicot - two cotyledons mature Three tissue systems: Dermal Vascular Cortex or Ground All cells of the primary growth in dicots are part of these three systems and originate at meristems. . . A reminder that endosperm is formed in all angiosperms, but does not persist in dicots. In dicots, cotyledons are the primary source of nutrients for germination.
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and root meristem
Seed germination What causes a seed to resume growth? What is growth? Broadly, where do the energy and basic elements required for growth come from? What observations did you make while germinating seeds? Plants-In-Motion Time-lapse videos of plant growth and response
Dicot germination and seedling An example of epigeous (epi=above, geo=earth) germination
Dicot germination and seedling An example of hypogeous (hypo=below, geo=earth) germination
Monocot germination and seedling
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
Root the first structure to emerge from the germinating seed Typical dicot Taproot persists and grows deep into the ground Typical monocot Taproot does not persist and adventitious roots originate from the shoot Notice the high surface volume: area ratio
Tap Root vs. Fibrous Root What are the functions of roots? From Outlaw lecture Typical of a dicot Typical of a monocot
Organization of the plant body Root apical meristem Meristem = group of perpetually “embryonic” cells Apical = at the tip (of the root, the shoot, including laterals)
The rootcap and mucigel protect the root apical meristem as it pushes through the soil Mucigel
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
All cells of primary growth are from one of three primary tissues
Diagram of major parts of primary dicot plant body Ground tissue
Ground tissue of typical dicot root and shoot Root Buttercup (Ranunculus) Shoot Alfalfa (Medicago)
All cells are from one of three primary tissues
Diagram of major parts of primary dicot plant body Vascular tissue
Vascular tissue of typical dicot root Root Buttercup (Ranunculus)
Vascular tissue of typical dicot shoot Shoot Alfalfa (Medicago)
All cells of primary growth are from one of three primary tissues
Diagram of major parts of primary dicot plant body Dermal tissue
Ground tissue of typical dicot root and shoot Root Buttercup (Ranunculus) Shoot Alfalfa (Medicago)
Specialized dermal cells in the shoot - a preview of next week’s topics The structure of the leaf and aspects of stomatal physiology will be topics of study next week
Specialized epidermal cells Venus flytrap
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
Root Hairs—a special feature of roots (a) Radish (Raphanus) Bentgrass (Agrostis)
Root Hairs—a special feature of roots (b) Cell Elongation Cell Division
Root Hairs—a special feature of roots (c) More than with shoots, elongation growth is restricted to very near (~1. 5 mm) the root tip; otherwise, elongation would tear off lateral appendages. Root hairs increase surface area.
Typical dicot root Root Buttercup (Ranunculus)
The endodermis Casparian Strip—a band of hydrophobic material (mostly suberin) that is impregnated in the wall, preventing apoplastic transport. From Outlaw’s lecture
The endodermis Three pathways for entry into xylem transport: all require that the solute be transported into the symplast (because the apoplast is discontinuous at the endodermis). Then, solutes are excreted into the apoplast interior to the endodermis. Apoplast Symplast From Outlaw’s lecture
Typical dicot root Root Buttercup (Ranunculus)
Secondary Growth (root) Example cross section of the dicot root in primary growth The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either: A secondary xylem cell to the inside and a replacement cambial cell. OR A secondary phloem cell to the outside and a Secondary growth rare in monocots replacement cambial cell. From Outlaw’s lecture
The pericycle Ordinarily, lateral roots arise in the pericycle. But roots can arise adventitiously, too. (Adventitious simply means arising in an unusual location. ) Salix (Salicaceae family) From Outlaw’s lecture
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
Mangrove (a dicot) Support roots in the marsh habitat. From Outlaw’s lecture Interesting Examples
Orchid (a monocot) Aerial roots absorb water from the air and have a multi-layered epidermis for protection and reduced water loss Interesting Examples Cross section of root Epidermal layers
Flower pot plant (an epiphyte) Interesting Examples Modified leaves form hollow containers that roots grow into and that collect rainwater and debris. Many ants associate with these plants, likely adding to nitrogen supply
Today • Review seeds and the life cycle of plants • Seed germination • Roots and root meristem • The three primary tissues • Specialized cells in primary root tissues • Interesting examples of root function and adaptations • Shoot and shoot meristem
The shoot What are the functions of the shoot?
Primary tissues differently organized in angiosperm shoots Typical of dicots Typical of monocots
Primary tissues differently organized in angiosperm shoots Example dicot stem cross section vascular bundles in ring with defined pith and cortex Shoot Alfalfa (Medicago)
Primary tissues differently organized in angiosperm shoots Example monocot stem cross section vascular bundles scattered Maize (Zea)
Apical Meristems both have three primary tissues Root Radish (Rafarus) Shoot Lilac (Syringa)
Lilac (Syringa) Block Diagram of Typical Shoot Apical Meristem Primary meristems give rise to primary tissues Modified from Outlaw’s lecture
Secondary Growth (shoot) Example cross section of the dicot shoot in primary growth The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either: A secondary xylem cell to the inside and a replacement cambial cell. OR A secondary phloem cell to the outside and a replacement cambial cell. From Outlaw’s lecture
The main idea
Important Announcement/Reminder Review photosynthetic electron transport and photosynthetic carbon metabolism from BSC 2010. Instead of reviewing your 2010 notes/text, you may refer to Outlaw’s website: http: //bio. fsu. edu/~outlaw/courses/BSC_3402 L/ And select Scientific Background.
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