Chapter 5

 Acquired primarily through the roots  Inorganic ions  Nutrient cycles begin with plant roots – mining minerals from the soil  Soil mycorrhizza & N-fixers assist  Research central to Ag and environmental protection 2

 Crop plants utilize < 50% applied fertilizers  Leech into ground water (spoiling wells)  Attached to soil particles (N availability)  Contribute to air pollution  OTOH ….. phytoremediation 3

 “intrinsic component in the structure or metabolism of a plant or whose absence causes severe abnormalities in plant growth, development, or reproduction”  C. HOPKiNS CaFe. Mighty good!  (Macro- VS Micro-nutrients) VS Function 4

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1.Part of carbon compounds a)Assimilated via ReDox rxns 2.Important in energy storage or structural integrity a)Typically as phosphate, borate, & silicate 3.Remain in ionic form a)Enzyme cofactors & regulation osmotic potential 4.Involved in ReDox reactions 7

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 Nutrient deficient solutions  Modified Hoagland – Complete Nutrition  Macronutrients: K, NO 3, Ca, NH 4, PO 4, MgSO 4  Micronutrients: KCl, BO 3, Mn, Zn, Cu, SO 4, Mo, Fe  Optional: Ni, Na, Si 11

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 Typically characteristic symptomology  Occur simultaneously in different tissues  Defficiencies/excesses can induce deficiencies/excesses in other nutrients  Viral infections mimic nutrient deficiencies 15

 Essential element mobile – old leaves first  Essential element non-mobile – young leaves 16

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 From the Hopkins text ….  Macronutrient – required in large amounts  In excess of 10mmole/kg of dry weight  Generally involved in structure of molecules  Micronutrients – small amounts  Less than 10 mmole/kg of dry weight  Catalytic and regulatory roles like enzyme acrivators  Beneficial – not universal or not detectable  Na, Si, Se, Co 20

 Na – essential for C4 plants  Si – 1-2% of dry matter Zea mays  Up to 16% (or more) of Equisetum  Cell walls of grasses to help against lodging  Co -- required for N-fixing bacteria  Se -- essential or tolerable?  Loco weeds! (up to 0.5%)  Only grow in high Se environments 21

 Macro-/micro- versus functional  Same nutrient often fills multiple roles!  Mg – component of chlorophyll; also enzyme cofactor in ionic form  Ca – component of cell walls; but also second messenger 22

 Critical concentrations – concentrations measured in the tissues below the level that gives maximum growth  Nutrient limits growth below critical concentration  Toxicity can be observed with micronutrients 23

 Sources and Uses  Constituent of many macromolecules  Proteins, nucleic acids, some hormones, chlorophyll  Absorbed in the form of NO 3 - and NH 4 +  Deficiency Symptoms  Slow stunted growth  Chlorosis of the leaves  Accumulation of anthocyanin pigments in stems/leaves  Excess N  Stimulates growth of the shoot system  Delays onset of flowering 24

 Sources and Uses  Nucleic acid backbone; metabolism; membranes  Soil pH major role in availability  Organic phosphates converted to inorganic forms  Most commonly limiting nutrient -- mycorrhiza  Deficiency Symptoms  Intense green leaves  Malformed leaves with necrotic spots  Accumulation of anthocyanin pigments  Excess  Stimulates growth of roots 25

 Sources and Uses  Activates enzymes; osmoregulation (stomates in particular)  Deficiency Symptoms  Marginal chlorosis followed by necrotic lesions  Increased suceptibility to root-rot 26

 Sources and Uses  Proteins (disulfide bridges), coenzymes (esp. A) and vitamins  Mustard oils in Brassicoids  Deficiency Symptoms  Not a common problem; appropriate forms produced by soil microorganisms  General chlorosis including tissues around X/P 27

 Sources and Uses  Important in cell division (mitotic spindle), cell adhesion (middle lamella), & second messenger  Deficiency Symptoms  Appear in meristems  Deformed and necrotic new leaves  Poor root growth 28

 Sources and Uses  Chlorophyll, reactions with ATP, and regulator of enzyme activity  Deficiency Symptoms  Chlorosis due to breakdown of chlorophyll between veins 29

 Sources and Uses  Of all micronutrients, required in largest amounts  Chlorophyll synthesis – but precise role is mystery!  Enzymes not Fe-dependent  T&Z says chlorophyll-protein complexes  Deficiency Symptoms  Loss of chlorophyll – intervenous spaces (serious leaves turn white)  Degeneration of chloroplast  Multiple strategies for enhancing uptake 30

 Sources and Uses  Cell division, elongation, and integrity of cell wall  Least understood  Deficiency Symptoms  Structural abnormalities of cell walls  Inhibition of both division and elongation in roots  Cell division in shoot apex and young leaves inhibited  Necrosis of the meristem  Shortened internodes & enlarged stems 31

 Sources and Uses  Cofactor for oxidative enzymes  Browning of apple and potato surfaces!  Deficiency Symptoms  Stunted growth, distortion of young leaves, and loss of young leaves. 32

 Sources and Uses  Activator for numerous enzymes  Deficiency Symptoms  Auxin metabolism  Shortened internodes and smaller leaves  Precise mechanism unclear! 33

 Sources and Uses  Enzyme cofactor  Part of Oxygen-evolving complex  Deficiency Symptoms  Aggravated by low pH and high organic content  “Gray speck” in cereal grains  Chlorosis between veins  Discoloration and deformities in legume seeds 34

 Sources and Uses  Key component of N metabolism  Deficiency Symptoms  In N-fixers can produce symptoms of N deficiency!  Young leaves twisted and deformed  Chlorosis and necrosis  Highly species dependent  Legumes, Brassicoids, and maize 35

 Sources and Uses  Oxygen evolution and charge balance across membranes  Deficiency Symptoms  Reduced growth, wilting of leaf tips, chlorosis 36

 Sources and Uses  Not clear  Ubiquitous in plant tissue – amt in seed sufficient!  Studies – multiple generations of Ni-deficient plants  Deficiency Symptoms  Low germination rates (< 12%)  increased Ni to 0.6 μM OR 1.0 μM -> 57% and 95%  Seedling vigor, chlorosis, necrotic lesions 37

 Micronutrients excellent examples of dangers of excesses  Critical toxicity level – 10% reduction in dry matter  Symptoms difficult to diagnose – excess of one nutrient causes deficiency in another  Typically inhibit root growth 38

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