Transcript natural resources

Agronomy
Management of the natural resources
used in food, feed and fiber production.
 “Making two blades of grass grow where
one once grew.”

Crop Science: Principles & Practice
Fifth 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.

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

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
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

The Plant Cell – p. 1
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

Monocot Seed Anatomy (corn) -3
Monocot Seed Anatomy (wheat) -3
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”

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%

Cereal Germination/Emergence -5
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

Cereal Germ./Emerg. II - 7
Legume Seed Anatomy
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

Legume (epigeal) Germ/Emerg -9
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
Legume (hypogeal) Germ/Emerg -9
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)

Leaves– comparing parallel-veined
leaves w/ netted-veined leaves -11
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.

Dicot leaf, view a -12
Dicot leaf, view b - 12
Monocot leaf -12
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)
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

Stomata -13
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
Parts of Grass Leaf -14
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
Parts of Legume Leaf -15
Stem Anatomy, longitudinal -16
Dicot stem, cross section -16
Monocot stem -17
Vascular bundle - 17
Modified Stems -18
Plant Roots -19
Root Systems -20
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
Grass & Legume Inflorescence -20
Moving = View, Slide Sorter,
Then click and drag.