Introduction to Plant Development Keep a green tree in your heart and perhaps the singing bird will come....Chinese proverb

Plant Biology and Related Fields Plant Biology Agriculture Pharmaceuticals Basic BiologyGenetics Molecular Cellular Biology Biotechnology Ecology Evolution Systematics

Already What are the major organ systems that make up the plant body? –what are the major functions of these organs? What are the three major tissues that make up plant organs? –which cell types comprise these tissues? –what are some functions of these cells? What cellular structures or cellular processes are unique to plants (or at least highly unusual compared with animals)?

Today and Monday How do plant organs, tissues and cells develop? –Examine Plant Growth, the irreversible increase in size that (in plants) almost always results from both cell division and cell enlargement, –Examine Plant Cell Differentiation, the process by which a cell acquires metabolic, structural and functional properties distinct from those of its progenitor, Development, –the sum total of events that contribute to the progressive elaboration of the body of an organism.

Developmental Programs Indeterminate growth/development, –capacity for g/d over an extended period of time, vegetative growth and flowering, –g/d is not genetically limited and can* continue as long as environmental conditions and resources permit. Determinate growth/development –g/d is genetically limited. Plants display great phenotypic plasticity due to a life-style of indeterminate growth and development. *plants have genetically limited life spans.

(Toti)potency …the potential of a single cell to become a progenitor for an entire organism (organ, tissue, or cell type), –growth and development are genetically and epigenetically controlled in all organisms, epigenetics: DNA methylation, chromatin remodeling, etc. -in contrast with most animals, plants retain the capacity to initiate developmental programs throughout their lives, -nucleated plant cells are (all) totipotent.

Stem Cells totipotent Blastocyst pluripotent animal development multipotent initials derivatives initials derivatives plant development …all nucleated plant cells are totipotent. initials Zygote ---> Several Div.

Apical-Basal Axial Development Arabidopsis Zygote (4h) Embryogenesis See fig. 23.5

Meristems... …persistent populations of small isodiametric cells with embryonic characteristics.

Apical Meristems cells that remain in the meristem are termed initials, cells that are displaced from the meristem and later differentiate, are called derivatives. Shoot Apical Meristem (SAM) Root Apical Meristem (RAM)

initials derivatives initials derivatives plant development …all nucleated plant cells are totipotent. initials Totipotency

Primary Meristems Derive from apical meristems and produce primary growth (apical-basal), –Protoderm: dermal meristem, –Procambium: vascular meristem, –Ground meristem.

Plant Cell Division Plasmodesmata

Apoplast / Symplast Symplast The interconnected protoplasts and their plasmodesmata. Apoplast The cell wall continuum of a plant. “Outside of the symplast.” Plant Structure

SAM Shoot Apical Meristem Distal: away from the point of reference, Proximal: situated near the point of reference (the main body), Central/Peripheral: “girth”, also termed lateral, Adaxial/Abaxial: ad (toward), ab (away).

Tunica / Corpus

Tunica Corpus

SAM Shoot Apical Meristem Primary Meristems

Study this one, and look at lab examples.

Leaf Development Tunica cells differentiate into a leaf founder cell, –divide more rapidly and form the leaf primordium, a meristem with determinate growth, Sub-organ domains develop, i.e. upper leaf, lower leaf, mesophyll, vasculature, etc. L1 (epidermis), L2 (ground tissue) and L3 (vasculature).

Phyllotaxy The number and order in which leaf primordia form is genetically determined and is generally characteristic of species.

Leaf Anatomy Study this slide. Review in lab. Ask questions? stomata

Developmental Plasticity I Sun Leaf Shade Leaf Thermopsis montana

Developmental Plasticity II

Mucilage Sloughing off Primary Root Morphology Fig

Root Morphology The Root Cap To reduce friction from growth in soil The root cap secretes mucilage The root cap sloughs cells The Zone of Mitosis (Meristematic) Makes new cells by Mitosis Meristematic Cells Divide by Mitosis The Zone of Elongation Cells Grow in Size Vacuole Appears and Grows Mature Organelles are Produced

RAM Root Apical Meristem See Fig

RAM Root Apical Meristem …produces new cells proximally and distally.

More Root Morphology Casparian Strip: …suberin (fatty) band around the endodermis. Endodermis:...innermost layer of the cortex. Stele: …central cylinder within roots and stems of dicots.

Primary Root Morphology Lateral roots form primary meristems in mature regions of roots, form new roots (organs).

Pericycle …outermost layer of the stele in roots, the source of nascent meristematic cells that gives rise to lateral roots, …root primordia form, …protoderm, ground meristem and procambium form, …root cap forms, pushes through the cortex, …vasculature forms between stele and differentiating derivatives of the root primordium.

Meristems know them Monday: lateral meristems (2 o growth).

Patterns of Development Zygote Embryo Cotyledons Hypocotyl Root Cotyledons Hypocotyl Root SAM RAM apical/basal, axial embryogenesis primary growth SAM Cell Differentiation Cell Differentiation Leaf Primordia Leaf Primordia Stem Tissues Stem Tissues 1 o Growth primary growth RAM Root Tissues Root Tissues ? ?? Structure/Function ? ? 1 o Growth 2 o Growth

Monday Read the rest of the chapter, Stump the me with questions?