Agronomy

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Agronomy

• Management of the natural resources used in food,
  feed and fiber production.
• Making two blades of grass grow where one once
  grew.

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Crop Science Principles PracticeFifth
Edition, by R. E. Mullen

• A copy has been requested to be placed on
  two-hour Reserve, in Marston Science Library
  (MSL).
• If you have a previous edition, Fourth or Third,
  the changes are not great but you would be
  well-advised to go to MSL and compare and note
  changes.

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Suggestions for success

• Stay ahead of lecture topic in your reading
• Attend class there will be information in class
  not in text and there will be text info that the
  instructor will not emphasize
• Review notes after class clarify what is not
  understood (text, friend, instructor)
• Study for quiz with one or two friends

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Anatomy

• Helps us understand plant behaviour
• Helps us make management decisions
• Helps us communicate with practioners
• - We get better answers when we ask more precise
  questions

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We will emphasize two families

• Monocotyledonous plants grasses
• - one seed leaf
• - all have hypogeal emergence
• Dicotyledonous plants broadleaf plants
• - legumes are dicots
• - two seed leaves
• - most are epigeal, but some are hypogeal
  emergence

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The Plant Cell p. 1
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Cell wall to emphasize

• Nucleus genetic material (DNA), contents
  determined by both parents
• Cytoplasm inherited from female only
• Ribosomes protein manufacture DNA
• Mitochondria respiration site DNA
• Chloroplast photosynthesis site DNA

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Monocot Seed Anatomy (corn) -3
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Monocot Seed Anatomy (wheat) -3
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Monocot Seed Highlights - I

• Caryopsis (pericarp is fused ovary tissue)
• Embryo tissue separate from storage tissue
  living tissue stains red with tetrazolium
• Wheat, rye and triticale contain gluten

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Monocot Seed Highlights -II

• Big three rice, wheat, corn (cereal)
• Cereal grass grown for edible seed
• Globally, 70 human diet are cereals
• Cereals store well, retain germination well
• Cereal protein content 7-17

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Cereal Germination/Emergence -5
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Germ./Emerge. Highlights, corn

• Mesocoty (first internode) pushes coleoptile to
  surface
• Sunlight hitting coleoptile is the stimulus for
  mesocotyl to stop growing, coleoptile to split,
  secondary roots (coronal, adventitious) develop
  at that point
• Primary root system radicle and seminal roots
  survive about three weeks

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Cereal Germ./Emerg. II - 7
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Legume Seed Anatomy
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Legume Seed Highlights

• Dicots two cotyledons
• True seed as the pod is the ovary and the seeds
  are the ovules
• Note the exposed position of the embryo axis
  susceptible to mechanical damage
• Note also that if cotyledons split, the epicotyl
  goes with one or the other

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Legume (epigeal) Germ/Emerg -9
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Legume Emerg. (hypogeal) Highlights

• Observe the difference vs the cereal emergence
  the legume pushes/pulls a huge mass to surface
  planting depth is more critical
• Note the helpful definition of two terms
• epi above
• hypo - below

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Legume (hypogeal) Germ/Emerg -9
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Legume Seedling Highlights

• Leaves are netted-veined in contrast to grasses
  which are parallel-veined
• Most legume leaves are compound that is they
  have two or more leaflets/leaf
• In soybeans, the first leaf is unifoliolate,
  subsequent leaves are trifoliolate . . .
  (careful with spelling, as similar spellings have
  very different meanings)

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Leaves comparing parallel-veined leaves w/
netted-veined leaves -11
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Practical leaf implications

• Herbicides often are broadly categorized as
  broadleaf herbicides or grassy weed herbicides
• The leaf is the first place we look for nutrient
  deficiency symptoms where on the leaf is the
  deficiency located? Where on the plant is the
  deficient leaf located? More on this later.

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Dicot leaf, view a -12
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Dicot leaf, view b - 12
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Monocot leaf -12
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Monocot leaf comments

• Note the bulliform cells when moisture
  deficient, these cells go flacid and the leaf
  rolls a self preservation mechanism that
  reduces moisture loss
• Water and mineral nutrients travel in xylem
• Photosynthates travel in phloem living cells.
  Foliar applied herbicides also travel in phloem
  which is one reason why rate of application is
  important (if herbicide kills phloem cells, will
  not be translocated to other plant organs and
  weed survives)

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Leaf comments

• Leaves of some species have additional features
  wax (moisture retention) or pubescence (depending
  on pest, trichomes may provide some resistance
  (e.g., leaf hoppers) or may contribute to
  susceptibility (e.g., spidermites)
• Leaves w/ no pubescence glabrous

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Stomata -13
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Stomata comments

• Stomata vary in density w/ plant species and from
  top to bottom of leaves, depending on plant
  species
• Stomata open when sufficient moisture present in
  guard cells to cause to swell (inside of guard
  cell wall thicker than outside and causes cell to
  curve when turgid), and with oxygen concentration
  in cells
• Not all gas (O2, CO2, H20) is exchanged thru
  stomata some passes thru epidermis

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Parts of Grass Leaf -14
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Grass leaf parts comments

• Leaf anatomy is important in species
  identification presence, shape and type of
  ligule, auricles, pubescence at the collar region
  help identify species.
• Tillers are like stem clones, multiples arising
  from one seed or crown area highly desirable in
  small grains.
• Stolons and rhizomes contribute to spread and
  in weeds, rhizomes make control more difficult

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Parts of Legume Leaf -15
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Stem Anatomy, longitudinal -16
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Dicot stem, cross section -16
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Monocot stem -17
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Vascular bundle - 17
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Modified Stems -18
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Plant Roots -19
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Root Systems -20
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Root System comments

• Type affects tolerance to moisture stress periods
  tap-rooted species generally root deeper, and
  if irrigated, need irrigation less often, but
  application amount is greater
• There are soil-building and carbon sequestration
  differences fibrous root systems deposit and
  distribute carbon more effectively think of the
  rich prairie soils

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Grass Legume Inflorescence -20
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