Soil Science/Grondkunde Factors of Plant Growth PDF

Chapter 12 Factors of plant growth Soil Science / Hoofstuk 12 die Faktore wat Grondkunde plantegroei beïnvloed 142 Defenisie van Groei Definition of Growth Verhoging in massa, Irreversible increase in lengte, grootte, volume mass, height, size, volume...

Chapter 12 Factors of plant growth Soil Science / Hoofstuk 12 die Faktore wat Grondkunde plantegroei beïnvloed 142 Defenisie van Groei Definition of Growth Verhoging in massa, Irreversible increase in lengte, grootte, volume mass, height, size, volume Hele plant of spesifieke Whole plant or specific dele (graan, vrugte, ens.) parts (grain, fruit, etc.) Patroon is gewoonlik Pattern normally sigmoïdaal met tyd sigmoidal with time (versnelling en dan (accelerating then braking) remming) In response to factors Is gehoorsaam aan die affecting it, obeys law of reël van verminderende diminishing returns opbrengste, in reaksie teenoor faktore wat dit beïnvloed Liebig se Wet van die Minimum Liebig’s Law of the Minimum “Groei eweredig sal wees aan daardie faktor waarvan daar relatief die minste teenwoordig is". “Growth will be proportional to the factor that is relatively N least present” – most limiting factor Faktore Wat Groei Beïnvloed Factors Influencing Plant Growth Klimaat Faktore Grond Faktore Biotiese Faktore Climate Factors Soil Factors Biotic Factors Neerslag Voedingstowwe / Nutrients Spesie/Variteit (Geneties) Precipitation Species/Variety (Genetic) Temperatuur /Temperature Tekstuur / Texture Plantdigtheid / Planting density Humiditeit / Humidity Struktuur / Structure Saad kwaliteit/Seed quality Lig / Light (Intensity, quantity, KUK (%BV) & pH / Insekte / Insects duration) CEC (%BS) & pH Atmosfeer samestelling / Grondtemperatuur / Pathogene / Pathogens Atmosphere composition Soil temperature Wind Diepte / Depth Onkruid / Weeds Dreineering / Drainage Bewerkingspraktyke / Cultivation practices Brakheid / Salinity Noodsaaklike Plantvoedingstowwe Essential Plant Nutrients Makroelemente Macro-elements C H O (struktureel) C H O (structural) N P K (primêr) N P K (primary) Ca Mg S (sekondêr) Ca Mg S (secondary) Spoorelemente Trace elements Cu Fe Zn Mn (kationies) Cu Fe Zn Mn (cationic) B Mo Cl (anionies) B Mo Cl (anionic) Ander: Na Co Va Si (some plants) Other: Na Co Va Si (some plants) Samestelling van Plante Composition of Plants Water 70 - 95% van vars Water 70 - 95% of fresh materiaal matter Organiese verbindings Organic compounds (CHNO) (CHNO) 90 - 95% 90 - 95% As samestelling (anorganies) Ash component (inorganic) 5- 5-10% van droë materiaal (K, Na, 10% of dry matter (K, Na, Ca, Mg, Ca, Mg, S, P, Si, Fe, Mn, Cu, Zn, B, S, P, Si, Fe, Mn, Cu, Zn, B, Mo, Cl, Mo, Cl, Ni, V, Cr, Si, Au, Ag, As, Al, Ni, V, Cr, Si, Au, Ag, As, Al, Co, Se Co, Se ens.) etc.) Wanneer is ‘n element noodsaaklik? When is an element essential? Drie kriteria: Three criteria: Tekort maak dit vir Deficiency implies die plant ontmoontlik om impossible completion of sy normale lewe te normal life voltooi Deficiency symptom Tekortsimptoom kan only correctable with net gekorrigeer word met that element die spesifieke element Must have a metabolic Moet 'n metaboliese function funksie hê Voedingstof Vlakke Nutrient Levels Tekort: konsentrasie van Deficient: concentration of noodsaaklike element is laag essential element is low enough genoeg om opbrengs te beperk to severely limit yield – distinct – toon spesifieke deficiency symptoms or “hidden tekortsimptome of “versteekte hunger” honger” Critical range (Cultivar specific): Kritiese Bereik: voedingstof nutrient concentration in the konsentrasie in die plant plant below which a yield waaronder ‘n verandering in response to added nutrient opbrengs waargeneem word as occurs – transition from voedingstof toegevoeg word – deficiency to sufficiency oorgang van tekort na voldoende bereik  Voldoende: voedingstof bereik Sufficient: nutrient range in waar toegediende voedingstof which added nutrient will not nie opbrengs verhoog nie, maar increase yield but can still nog altyd deur die plant increase nutrient absorption by opgeneem word – “luukse plant – “luxury consumption” opname” Excessive or toxic: nutrient Oormaat of toksisiteit: concentration of element is high voedingstof konsentrasie is enough to reduce plant growth hoog genoeg om plantegroei (yield) (opbrengs) te laat afneem Toksisiteit Toxicity Mn toksisiteit / Mn toxcity Alle elemente (selfs All elements (even essential noodsaaklike) en baie ander ones) and innumerable verbindings kan toksies wees compounds can be toxic Spesiale gevalle in gronde: Al, Special cases in soils: Al, Mn, Mn, Zn, ander metale; Zn, other metals; Onderskeiding tussen Distinction between toxicity toksisiteit en onbalans and imbalance (antagonism) (antagonisme) Plant assesering Plant assessment Visuele tekort simptome kan Visual deficiency symptoms can moelik wees om te interpreteer be difficult to interpret or too Baie probleme het dieselfde late too correct simptome, b.v., P tekort en koue- Many problems result in same of water-stres symptoms, e.g., P deficiency, cold Veldtoets (vinning maar nie baie or water stress akkuraat nie) Field tests (quick but not very Selsap toetse accurate) Labratorium toetse (stadig, Cell sap tests (colorimetric kits) maar akkuraat, wye reeks Laboratory tests (slow, but elemente) accurate, wide range of Suurverteering van gedroogte elements) plantmateriaal Acid digestion of dry, ground Element bepaling met met AAS of plant material ICP-MS Elemental analysis using AAS or ICP-MS Voorsiening van voedingstowwe vanuit gronde Supply of nutrients from soils 1. Uitruilsetels (KUK - basiese katione & 1. Exchange sites (CEC - basic cations & NH4+, AUK - NO3-, Cl-, SO42-) NH4+, AEC - NO3-, Cl-, SO42-) – Reserve of Minerale nutrients Organiese Materiaal Minerals Plantwortels Organic matter 2. Mineraal verwering (basiese katione, Roots mikro-elemente) 2. Mineral weathering (basic cations, Mineraal oplosbaarheid (Ksp) micronutrients) Mineraal elementale samestelling bv. Mineral solubility (Ksp) mika Mineral elemental composition e.g. 3. Grond organiesemateriaal afbreek mica (N, P, S, makro en mikro-elemente) 3. Organic matter decomposition Mikrobiese aktiwiteit (N, P, S, macro and micronutrients) Mineralisasie Microbial cycling Humifikasie Mineralization Immobilisasie Humification 4. Voordelige Mikrobes (N, P, mikro- Immobilization elemente) 4. Beneficial Microorganisms (N, P, N-fikseerders (Risobium, asetobakter) micronutrients) Mikorisas N-fixers (Rhizobia, azotobacter) Mycorrhizae Beweging van ione na worteloppervlak Movement of ions to root surface 1. Wortel onderskepping: 1. Root interception: fisiese kontak tussen die physical contact between the wortels en root and mineral surfaces – mineraaloppervlakke – contact exchange occurs kontak uitruiling vind plaas 2. Mass flow: passive 2. Massa vloei: passiewe movement of ions in soil beweging van ione in grond- solution towards roots due to oplossing na plantwortels as transpirational water uptake gevolg van water opname by the plant gedurende transpirasie 3. Diffusion: active 3. Diffusie: aktiewe migrasie migration of ions across a van ione oor 'n konsentrasie concentration gradient (high gradient (hoog → laag) → low) Wortel kontak uitruiling Root contact exchange Significance of root interception, mass flow and diffusion in ion transport to maize roots (soil and root dependant)  Wortel Intersepsie van ione Root Interception of ions Plant aanpassing om Plant adaptation to facilitate voedingstofinname te bevorder nutrient capture 1. Wortelstruktuur: 1. Root structure: Veselagtige, vertakte Fibrous, branching root wortelsisteme meer doeltreffend systems more efficient Eensaadlobbig vs. Monocots vs. dicots tweesaadlobbig Root hairs Wortelhare Plant aanpassing om Plant adaptation to facilitate voedingstofinname te bevorder: nutrient capture: 2. Simbiose: bv. peulplante en 2. Symbioses: e.g. legumes and Rhizobia (sien Hoofstuk 4: N) Rhizobia (see Chapter 4: N) 3. Mikorisas: Ekto- and 3. Mycorrhizae: Ecto- and endotrofiese tiepes; funksies soos endotrophic types; function like root dié van wortelhare (sien Hoofstuk 5: hairs (see Chapter 5: P) P) 4. Rhizosfeer effekte: Grond wysiging (pH, voedingstowwe, eksudate, pCO2) vir gemeenskaplike bevoordeling van plant en mikro-organismes in die zone rond om die wortel (b.v. Azotobacter spp.) Rhizosphere effects: Soil modification (pH, nutrients, exudates, pCO2) for mutual benefit of plant and microorganisms in the zone surrounding root (e.g. Azotobacter spp.) Effek van plantwortels op Effect of plant roots on nutrient voedingstof vrystelling in grond release in soil Eksudasie en ioon uitruiling Exudation and ion uptake (handhawing van lading balans): (maintains charge balance) H+ vir katione H+ for cations HCO3- en organiese ligande vir anione HCO3- and organic ligands Selle pomp protrone uit om for anions katione vanaf KUK setels uit te ruil Cells pump out protons to Versuring van risosfeer lei tot exchange cations on CEC sites verhoogde oplosbaarheid van Acidification of rhizosphere results increased solubility of minerals minerale Organic ligands increase solubility of Organiese ligande verhoog metals die oplosbaarheid van metale Ioon absorpsie deur plante Ion absorption by plants Water en ioon opname deur Water and ion uptake by roots wortels (Wortelhaar sone) (Root hair zone) Apoplastiese vervoer (jong Apoplastic transport (young tissues): weefsels): Free movement of water through Vrye beweging van water deur intercellular spaces via capillary intersellulêre spasies via kapillêre action and osmosis into xylem aksie en osmose Casparian bands not fully Kaspariesebande in jong weefsels developed in young tissues is nie teen volle ontwikkel nie Symplastic transport: Simplastiese vervoer: Casparian bands act as Kaspariesebande tree op as ‘n impermeable barrier which ondeurdringbare versperring, wat allows endodermis to select and ioon absorpsie deur die regulate ion absorption endodermis reguleer Thus water transported across Dus word water oor die plasma- plasma membranes to xylem membrane vervoer na die xylem Passiewe en aktiewe ioon opname deur selle Passive and active ion uptake by cells Plasmamembrane is selektief Plasma membranes are selectively deurlaatbare membrane in plantselle permeable membranes in plant cells Deurlaatbaar : O2, CO2, sommige Permeable: O2, CO2, some neutral neutrale verbindings, water (min) compounds, water (slightly) Ondeurlaatbaar: anorganiese ione en Impermeable: inorganic ions and klein organiese verbindings small organics Dus word protïene benodig om H+, Thus, proteins are required to ione en ander organiese verbindings transport H+, ions and organic oor membrane te vervoer solutes across membrane Vervoer word deur elektrochemiese Transport is driven by electrochemical gradiente gedryf (aktief of passief) driving force (active or passive) Passief: diffusie gedryf, d.w.s., ioon Passive: diffusion driven, i.e. ions beweeg van [hoog] → [laag] move from [high] → [low] Aktief: ione word teen die Active: ions moved against konsentrasiegradient beweeg concentration gradient (requires (benodig energie) energy) Passiewe transport Passive transport Diffusie gedrewe vervoer Diffusion driven transport 1. Eenvoudige diffusie (b.v. CO2) 1. Simple diffusion (e.g. CO2) 2. Gefasiliteerde diffusie – kanaal 2. Facilitated diffusion -channel protïene (menige ione beweeg proteins (many ions move deur kanaal terselfde tyd, b.v. through channels at once, e.g., K+) K+) 3. Vervoerprotïene (1-2 ione op ‘n 3. Transporter proteins (1-2 ions at slag) a time) 1. Univoerders (b.v. glukose) 1. Uniporters (e.g., glucose) 2. Antivoerders (selfde gelaaide 2. Antiporters (same charged ions ione ruil uit, b.v., H+ en Na+) swap, e.g., H+ and Na+) 3. Simvoerders (teenoorgesteld 3. Symporters (oppositely charged gelaaide ione beweeg saam, b.v. ions move together, e.g., H+ and H+ en NO3-) NO3-) Energie vir anti- en sim-voerders Energy for anti- and sym-porters kom meestal van H+ of HCO3- comes from H + or HCO3- Aktiewe vervoer Active transport Groter, sterker gelaaide molekule Larger, more charged molecules (suikers, aminosure, DNA, ATP, (sugars, amino acids, DNA, ATP, fosfaat ione, protïene, ens.) phosphate, proteins, etc.) ATP-gedrewe pompe wat ione teen Involves ATP-powered pumps that konsentrasie gradiente vervoer transport ions against H+ ATP pompe pomp H+ na concentration gradients sitoplasma en vakuole H+ ATP pumps pump H+ into Na+-K+ ATP pompe is NB om cytoplasm and vacuole elektriese potensiaal gradiente oor Na+-K+ ATP pumps are NB for plasmamembrane te behou maintaining electrical potential Ca+ ATP pompe pomp Ca uit gradient across the plasma sitoplasma om konsentrasie membrane gradient te skep vanaf Ca+ ATP pumps pump out Ca from ekstrasellulêreruimtes cytoplasm to ensure concentration gradient from extracellular area Aktiewe vervoer Active transport Blad opname Foliar absorption Voedingstowwe kan deur blare Nutrients can be taken up through opgeneem word leaves Tempo van absorbsie is gewoonlik Rate of absorption normally too te stadig vir makro-element voorsiening low for macronutrient supply Belangrik vir die toediening van Important for application of some sommige spoorelemente- micronutrient fertilizers to crops bemestingstowwe aan gewasse (veral (especially when soil conditions limit waneer grondtoestande die solubility, e.g., Fe, Mn, Cu, Zn in oplosbaarheid benadeel, b.v., Fe, Mn, calcareous, high pH soils) Cu, Zn by kalkryke, hoë pH gronde) Can be applied with pesticides Kan tesame met insekdooders toegedien word