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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.”. Crop Science: Principles & Practice Fifth Edition, by R. E. Mullen.
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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.”
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.
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
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 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%
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
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 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 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.
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 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
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
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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