Potassium: Potash, from the ashes in the pot Potassium is an essential macronutrient Enhances fertility Promotes stress tolerance
Regulates enzyme activities Strengthens cell walls Stimulates photosynthate translocation
Maintains turgor and reduces wilting Regulates stomatal conductance, photosynthesis and transpiration
Symptoms of potassium deficiency
Maintains ionic balance [K+] in soil = ~0.1 – 1 mM [K+] in plant cell cytoplasm = ~100 mM
See Wang, M., Zheng, Q., Shen, Q. and Guo, S. (2013). The critical role of potassium in plant stress response. Intl. J. Mol. Sci. 14: 7370-7390; Sin Chee Tham /Photo; Purdue extension; Onsemeliot.
© 2014 American Society of Plant Biologists
Potassium fertilizers are mined from underground reserves as “potash” Potash is a term that encompasses many forms of potassium: • KCl (potassium chloride, aka sylvite) • K2SO4 (potassium sulfate) • K2CO3 (potassium carbonate) • K2Ca2Mg(SO4)4·2H2O (polyhalite) • etc.
Almost half of the world’s reserved of potash are found in Saskatchewan, Canada
KCl, sylvite For historical reasons, potash is measured in units of K2O equivalents, even though it is rarely found in the form of K2O Canada Potash; Lmbuga
© 2014 American Society of Plant Biologists
Potash provides K for fertilizers, which supplement natural sources Water pumped underground
Water with dissolved K+ salts returned to surface
Potash fertilizer application
Salts recovered by evaporation
Underground reserves
0.1 – 0.2% soil solution K+ 1 – 3% exchangeable salts
manure decomposition
Terrestrial cycle: Plant / Animal / Soil
90 – 98% insoluble minerals Adapted from International Potash Institute
© 2014 American Society of Plant Biologists
Potash prices can be volatile and there are few suppliers Canada is #1 in production (11.2 Mt) and reserves (4,400 Mt)
Spain 0.4 Mt 20 Mt Germany 3.3 Mt 150 Mt
US 1.1 Mt 130 Mt
Chile 0.8 Mt 130 Mt
Brazil 3.2 Mt 210 Mt
Russia is #2 in production (7.4 Mt) and reserves (3,300 Mt)
Belarus 5.5 Mt 750 Mt
UK 0.4 Mt 22 Mt 1.0 6 cm
China 3.2 Mt 210 Mt
Israel 2.0 Mt 40 Mt
Jordan 1.4 Mt 40 Mt
World reserves 9500 Mt World production (2011) 37 Mt
Adapted from International Potash Institute
© 2014 American Society of Plant Biologists
Potassium is an essential plant nutrient K+ is a counter ion for negatively charged molecules including DNA and proteins K+ moves in and out of the vacuole through specific transporters
K+ uptake involves high and low affinity transporters
K+ is a cofactor for some enzymes
As the major cation in the vacuole, K+ contributes to cell expansion and movement, including that of guard cells
Reprinted from Maathuis, F.J.M. (2009). Physiological functions of mineral macronutrients. Curr. Opin. Plant Biol. 12: 250-258 with permission from Elsevier.
© 2014 American Society of Plant Biologists
Early studies of potassium uptake in plants: Biphasic uptake Co-transporter mediated 2 x ATP K+ H+
High affinity transport
Low affinity transport
KCl (mM)
Epstein et al showed two phases of K+ uptake in barley roots
High affinity transport
2 x H+
Channel mediated ATP
K+
H+
Low affinity transport
K+ uptake from low [K+]ext requires more energy than when [K+]ext is higher
Epstein, E., Rains, D.W., and Elzam, O.E. (1963). Resolution of dual mechanisms of potassium absorption by barley roots. Proc. Natl. Acad. Sci. USA. 49: 684 – 692; Gierth, M. and Mäser, P. (2007). Potassium transporters in plants – Involvement in K+ acquisition, redistribution and homeostasis. FEBS Lett. 581: 2348-2356.
© 2014 American Society of Plant Biologists
K+ mobilization is critical for K+ use efficiency Supraoptimal K +
can be stored in the vacuole Cytosol Vac.
As K+ becomes limiting, it becomes preferentially allocated to the cytosol
Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.
© 2014 American Society of Plant Biologists
K+ mobilization is critical for K+ use efficiency As K+ becomes limiting, it becomes preferentially allocated to the cytosol
Cytosol Vac.
K+ can be remobilized from less essential tissues into prioritized tissues such as growing and photosynthetic tissues
Prioritized
NonPrioritized
Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.
© 2014 American Society of Plant Biologists
Summary: Potassium uptake, transport and regulation • Potassium is an essential macronutrient required in large amounts • Potassium uptake involves low and high affinity transporters • K+ uptake, transport and remobilization are regulated extensively to ensure that the plant’s critical tissues are preferentially supported
© 2014 American Society of Plant Biologists
Sulfur: Clean air can lead to deficient plants Sulfur dioxide damage
Until recently, sulfur dioxide emission from fossil fuel combustion led to acid rain and extensive damage to vulnerable plants
Eliminating S from air pollution uncovered crop plant deficiencies, particularly in oilseed rape and wheat
International Society of Arboriculture; Robert L. Anderson, USDA Forest Service; D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes in oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.
© 2014 American Society of Plant Biologists
Sulfur can be found in many inorganic forms Species S2-, H2S, R-SH S0 , S 8 SO2 SO3SO42-
Name Sulfide Sulfur Sulfur dioxide (toxic gas) Sulfite Sulfate
Oxidation State -2 0 +4 SO42+4 +6
Organic S R-SH SO3H2S
Plants take up sulfur from soil as SO42- and to a lesser extent from the atmosphere as SO2 or H2S S0
Sulfur deposits © 2014 American Society of Plant Biologists
Plants are an important part of the global sulfur cycle Atmospheric pool of sulfur – mostly SO2 (sulfur dioxide) Volcanic activity
Combustion of fossil fuels
H2S
SO2
O2 H2O
SO42-
Acid rain*
manure
R-SH
decomposition
S
Assimilation by plants
SO42-
Prokaryotic oxidation
SO42-
*Since the 1980s, SO2 emissions and SO42- precipitation have been declining
Prokaryotic reduction See for example Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
© 2014 American Society of Plant Biologists
Sulfur is an essential macronutrient in amino acids & other compounds HS-CH2-CH-COOH NH2 Cysteine (Cys)
Amino acids
Flavor or odor
S
S
Allicin (garlic flavor) O
H3C-S-CH2-CH2-CH-COOH NH2
SH S Mercapto-pmenthan-3-one (blackcurrant)
S Allyl-isothiocyanate (horseradish flavor)
Methionine (Met) S
Cys Glutathione Glutathione is an amino acid derivative involved in Redox reactions
Oxidation /reduction, metal transport and detox
Defense
S
Camalexin is a defense compound induced by pathogens
Glucosinolates are anti-herbivores S
McGorrin, R.J. (2011). The significance of volatile sulfur compounds in food flavors. Volatile Sulfur Compounds in Food. ACS Symposium Series, Vol. 1068: 3-31
© 2014 American Society of Plant Biologists
Sulfate uptake occurs primarily through SULTR transporters In Arabidopsis, 12 genes encode SULTR transporters that fall into four groups
Most are 12-membrane spanning SO42- / H+ co-transporters
SO42- H+ SO42- H+
Primary assimilation in roots occurs mainly through SULTR1;1 and SULTR1;2 Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 with permission from Oxford University Press; Smith, F.W., Ealing, P.M., Hawkesford, M.J. and Clarkson, D.T. (1995). Plant members of a family of sulfate transporters reveal functional subtypes. Proc. Natl. Acad. Sci. USA 92: 9373-9377. Rouached, H., Secco, D. and Arpat, A.B. (2009). Getting the most sulfate from soil: Regulation of sulfate uptake transporters in Arabidopsis. J. Plant Physiol. 166: 893-902. Gojon, A., Nacry, P. and Davidian, J.-C. (2009). Root uptake regulation: a central process for NPS homeostasis in plants. Curr. Opin. Plant Biol. 12: 328-338.
© 2014 American Society of Plant Biologists
In higher plants, SULTR transporters effect inter-organelle movement [SO42-] ≤ 10 μM
SULTR
[SO42-] 6 – 75 mM SO42- H+
Plastid
SO4
STORAGE
2-
S2-
Sulfate reduction only occurs in plastids
H+
Vacuole
SO42H+
[SO42-] 4 – 12 mM
SULTR
SO42-
SULTR Cytosol
[SO42-] 1 – 11 mM
Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773; Gigolashvili, T. and Kopriva, S. (2014). Transporters in plant sulfur metabolism. Frontiers in Plant Science. 5: 442. Rennenberg, H. and Herschbach, C. (2014). A detailed view on sulphur metabolism at the cellular and whole-plant level illustrates challenges in metabolite flux analyses. J. Exp. Bot. 65 : 5711-5724.
© 2014 American Society of Plant Biologists
S transporters coordinate long-distance transport too
Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 by permission of Oxford University Press.
© 2014 American Society of Plant Biologists
Primary sulfur metabolism (overview)
Uptake
Adenosine 5'-phosphosulfate
5'-Phosphoadenosine 3'-phosphosulfate
Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
© 2014 American Society of Plant Biologists
Sulfate is assimilated by ATP sulfurylase into APS ATP sulfurylase
+ Sulfate
+ ATP
This reaction occurs in the cytosol and plastid
Pyrophosphate (PPi)
Adenosine 5'phosphosulfate (APS)
Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
© 2014 American Society of Plant Biologists
APS can enter two pathways for primary or secondary reactions FdxOx
AMP
GSSG FdxRed 2 GSH
SO32-
APS reductase
APS kinase
Adenosine 5'phosphosulfate (APS)
Sulfite
Sulfite reductase
S2Sulfide Cysteine
Located exclusively in plastids
ATP ADP
Sulfated compounds, glucosinolates
5'-Phosphoadenosine 3'phosphosulfate (PAPS) Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
© 2014 American Society of Plant Biologists
Sulfide is assimilated into cysteine by the cysteine synthase complex Adenosine 5'phosphosulfate (APS)
(thiol)lyase (OAS-TL)
Cysteine synthase is a complex of SAT and OAS-TL, and is present in the cytosol, plastid and mitochondria
O-acetylserine (OAS) indicates cellular S status: when S is low, OAS accumulates Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from Elsevier.
© 2014 American Society of Plant Biologists
Model for regulation of cysteine synthesis by the CS complex When SO42- is available, free OAS-TL dimers produce cysteine
CS
SAT
OAS-TL is inactive within the CS complex
OAS is synthesized by SAT within the cysteine synthase (CS) complex Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from Elsevier.Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
© 2014 American Society of Plant Biologists
Model for regulation of cysteine synthesis by the CS complex When SO42- is unavailable, OAS accumulates, causing the CS complex to dissociate, and decreasing the activity of SAT. Thus, the rate of production of OAS decreases
Free SAT is deactivated
Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
© 2014 American Society of Plant Biologists
Sulfur uptake and assimilation rates are metabolically regulated SO42-out
SULTR SO42-in ATP Sulfurylase
Transcriptional, posttranscriptional and posttranslational / allosteric regulation of transporters
OAS Transcriptional regulation of ATP sulfurylase and adenosine 5'phosphosulfate (APS) reductase (APR)
APS Reductase SO3Cys Synthase Cys
Local sulfate levels
OAS Allosteric interactions, metabolic regulation
Reduced sulfur (glutathione, Cys etc) Light, carbon and nitrogen reserves, circadian rhythms etc)
Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184; Davidian, J.-C. and Kopriva, S. (2010). Regulation of sulfate uptake and assimilation—the same or not the same? Mol. Plant. 3: 314-325. Yi, H., Galant, A., Ravilious, G.E., Preuss, M.L. and Jez, J.M. (2010). Sensing sulfur conditions: Simple to complex protein regulatory mechanisms in plant thiol metabolism. Mol. Plant. 3: 269-279.
© 2014 American Society of Plant Biologists
SLIM (EIL3) coordinates many transcriptional responses to S Thioglucosidase activity (increased by Sdeficiency) liberates S for recycling
SLIM = Sulfur Limitation Red, pink = up-regulated by S-deficiency Blue = down-regulated by S-deficiency
Maruyama-Nakashita, A., Nakamura, Y., Tohge, T., Saito, K. and Takahashi, H. (2006). Arabidopsis SLIM1 is a central transcriptional regulator of plant sulfur response and metabolism. Plant Cell. 18: 3235-3251.
© 2014 American Society of Plant Biologists
Addressing S deficiency in plants With stricter laws on S emissions, less S enters soils and plants are more prone to S deficiency
S sufficient
S deficient
Soil can be augmented with elemental sulfur, ammonium sulfate or other fertilizers
D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes in oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.
© 2014 American Society of Plant Biologists
Summary: Sulfur uptake and metabolism • Found in many redox forms and can be assimilated from atmosphere • Deficiency more common with cleaner air • SULTR transporter family primarily involved in uptake and transport • Uptake and assimilation into organic forms subject to positive and negative regulation
© 2014 American Society of Plant Biologists
Magnesium: The “forgotten element” Mg in solution is a divalent cation Mg2+
Soil magnesium is a result of rock weathering and Mg2+ from seawater
Serpentine 3MgO*2SiO2*2H2O
The Dolomite Mountains are named for the mineral dolomite MgCO3*CaCO3
Magnesite MgCO3 Didier Descouens; Ra’ike; chensiyuan; James St. John
© 2014 American Society of Plant Biologists
Magnesium is a cofactor for many enzymes and central to chlorophyll Mg2+ is a counter ion for the negative charges of ATP
Mg2+ is an essential activator for many enzymes including Rubisco
Mg2+ is central to chlorophyll Mg2+ stabilizes ribosome 3D structure
Jensen, R.G. (2000). Activation of Rubisco regulates photosynthesis at high temperature and CO2. Proc. Natl. Acad. Sci. USA 97: 12937-12938.
© 2014 American Society of Plant Biologists
Mg deficiency interferes with photosynthesis & C transport Effects of Mg deficiency
One symptom of Mg deficiency is high-light induced chlorosis
Reused with permission from Wiley from Cakmak, I. and Kirkby, E.A. (2008). Role of magnesium in carbon partitioning and alleviating photooxidative damage. Physiol. Plant. 133: 692-704; See also Verbruggen, N., and Hermans, C. (2013). Physiological and molecular responses to magnesium nutritional imbalance in plants. Plant Soil. 368: 87 – 99.
© 2014 American Society of Plant Biologists
Magnesium transporters move Mg2+ across membranes Mg transporters are different from other cation transporters but conserved across life domains
There are two known classes of Mg transporters: MRS/MGT MHX (Mg/H+ exchanger)
Proposed structure and mechanism of an MRS-type transporter
Reproduced from Hermans, C., Conn, S.J., Chen, J., Xiao, Q. and Verbruggen, N. (2013). An update on magnesium homeostasis mechanisms in plants. Metallomics. 5: 1170-1183 with permission of The Royal Society of Chemistry; Reprinted by permission from Macmillan Publishers Ltd Hattori, M., Tanaka, Y., Fukai, S., Ishitani, R. and Nureki, O. (2007). Crystal structure of the MgtE Mg2+ transporter. Nature. 448: 1072-1075.
© 2014 American Society of Plant Biologists
Magnesium uptake is mediated by the MRS / MGT family WT
MGT6 RNAi
MGT6 is induced in roots by low Mg and required for efficient Mg uptake
Gebert, M., Meschenmoser, K., Svidová, S., Weghuber, J., Schweyen, R., Eifler, K., Lenz, H., Weyand, K. and Knoop, V. (2009). A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis thaliana allows for growth in low-Mg2+ environments. Plant Cell. 21: 4018-4030. Mao, D., Chen, J., Tian, L., Liu, Z., Yang, L., Tang, R., Li, J., Lu, C., Yang, Y., Shi, J., Chen, L., Li, D. and Luan, S. (2014). Arabidopsis transporter MGT6 mediates magnesium uptake and is required for growth under magnesium limitation. Plant Cell. 26: 2234-2248.
© 2014 American Society of Plant Biologists
Aluminum toxicity is minimized by increased Mg uptake Al inhibits growth, especially in low pH soils where it is most soluble
Al tolerant
Al sensitive
Elevated Mg soil levels or uptake can minimize Al toxicity mainly through competition for uptake and molecular interactions
Delhaize, E., and Ryan, P.R. (1995). Aluminum toxicity and tolerance in plants. Plant Physiol. 107: 315 – 321. Bose, J., Babourina, O. and Rengel, Z. (2011). Role of magnesium in alleviation of aluminium toxicity in plants. J. Exp. Bot. 62: 2251-2264, by permission of Oxford University Press.
© 2014 American Society of Plant Biologists
Mg deficiency in plants contributes to Mg deficiency in animals Rapidly growing spring grass can be low in Mg, so grass-fed cattle can experience hypomagnesemia, a sometimes fatal condition called grass tetany
Mg2+
To ensure adequate dietary Mg2+, human diets should include nuts, legumes, leaves and whole grains Peggy Greb USDA
© 2014 American Society of Plant Biologists
Summary: Magnesium • Rarely limiting for plant growth • Mg2+ transporters are different from other cation transporters, but conserved across life domains • Elevated Mg2+ uptake can mitigate Al3+ toxicity • Humans and animals can suffer Mg deficiency if dietary sources are deficient
© 2014 American Society of Plant Biologists
Calcium: Low free cytosolic levels & functions in apoplast / vacuole Calcium stabilizes pectin in middle lamella of cell walls
Middle lamella
Primary wall
2 μm
Secondary wall
Cytosolic Ca2+ oscillations are second messengers in diverse responses
Capoen, W., Den Herder, J., Sun, J., Verplancke, C., De Keyser, A., De Rycke, R., Goormachtig, S., Oldroyd, G. and Holsters, M. (2009). Calcium spiking patterns and the role of the calcium/calmodulin-dependent kinase CCaMK in lateral root base nodulation of Sesbania rostrata. Plant Cell. 21: 1526-1540. Bose, J., Pottosin, I., Shabala, S.S., Palmgren, M.G. and Shabala, S. (2011). Calcium efflux systems in stress signalling and adaptation in plants. Front. Plant Sci. 2: 85. Persson, S., Caffall, K.H., Freshour, G., Hilley, M.T., Bauer, S., Poindexter, P., Hahn, M.G., Mohnen, D. and Somerville, C. (2007). The Arabidopsis irregular xylem8 mutant is deficient in glucuronoxylan and homogalacturonan, which are essential for secondary cell wall integrity. Plant Cell. 19: 237-255.
© 2014 American Society of Plant Biologists
90% of the plant’s calcium can be in the form of calcium oxalate crystals •
The crystals are formed by specialized cells called idioblasts
•
Calcium oxalate crystals can function in defense
•
Calcium oxalate crystals also can sequester excess calcium
Prismatic crystals from bean seed coat
Druse crystals from velvet leaf (Abutilon theophrasti)
Bundle of raphide crystals from grape leaf
Idioblasts are specialized cells that form calcium oxalate crystals and are illuminated by polarized light (RI = raphide idioblast DI = druse idioplast)
Webb, M.A. (1999). Cell-mediated crystallization of calcium oxalate in plants. Plant Cell. 11: 751-761; Franceschi, V.R. and Nakata, P.A. (2005). Calcium oxalate in plants: Formation and Function. Annu. Rev. Plant Biol. 56: 41-71. Kostman, T.A., Tarlyn, N.M., Loewus, F.A. and Franceschi, V.R. (2001). Biosynthesis of l-ascorbic acid and conversion of carbons 1 and 2 of l-ascorbic acid to oxalic acid occurs within individual calcium oxalate crystal idioblasts. Plant Physiol. 125: 634-640.
© 2014 American Society of Plant Biologists
Plants maintain very low levels of free cytosolic Ca2+ The concentration of free Ca2+ is ~ 10,000 fold lower in the cytosol than the apoplast The challenge at the plasma membrane is to maintain low free internal Ca2+ (in contrast to the situation for most other nutrients)
Stael, S., Wurzinger, B., Mair, A., Mehlmer, N., Vothknecht, U.C. and Teige, M. (2012). Plant organellar calcium signalling: an emerging field. J. Exp. Bot. 63: 1525-1542 by permission of Oxford University Press .
© 2014 American Society of Plant Biologists
Ca2+ transport systems include channels, pumps and antiporters
Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.
© 2014 American Society of Plant Biologists
Calcium deficiency causes cell wall defects and sometimes cell death Calcium is translocated in the xylem (apoplast) but not the phloem (symplast), meaning that it cannot be remobilized when external supplies are limited
Ca2+ deficiency in growing tissues causes weakness and death, leading to blossom end rot (left), tip burn (right) and bitter pit (bottom). Ca2+ deficiency also can result from a low rate of transpiration.
Ca2+
White, P.J. and Broadley, M.R. (2003). Calcium in plants. Ann. Bot. 92: 487-511. Maine.gov; David B. Langston, University of Georgia; University of Georgia Plant Pathology Archive Bugwood.org
© 2014 American Society of Plant Biologists
Calcium contributes to pectin crosslinking and stabilization Pectin is a galacturonic acid polymer. Calcium stabilizes the pectin and causes it to “gel”
Ca2+ interacting with pectin at tip of pollen tube Ca2+ Pectin
Molecular gastronomists react calcium with pectin-like polymers to produce interesting foods Middle lamella
Pectin is found in the middle lamella and the cell wall of a growing pollen tube
Sundar Raj AA, Rubila S, Jayabalan R, Ranganathan TV (2012) A review on pectin: Chemistry due to general properties of pectin and its pharmaceutical uses. 1:550 doi:10.4172/scientificreports.550 (adapted from Axelos and Thibault, 1991). Hepler, P.K. and Winship, L.J. (2010). Calcium at the cell wall-cytoplast interface. J. Integr. Plant Biol. 52: 147-160, with permission from Wiley.
© 2014 American Society of Plant Biologists
Calcium oscillations are mediated by ion channels, pumps and carriers Ca2+ oscillations contribute to guard cell functions
How Ca2+ oscillations are decoded remains incompletely resolved A model of the ionic fluxes that result in calcium oscillations around the nucleus during symbiotic interactions Venkateshwaran, M., Cosme, A., Han, L., Banba, M., Satyshur, K.A., Schleiff, E., Parniske, M., Imaizumi-Anraku, H. and Ané, J.-M. (2012). The recent evolution of a symbiotic ion channel in the legume family altered ion conductance and improved functionality in calcium signaling. Plant Cell. 24: 2528-2545. Evans, N.H. and Hetherington, A.M. (2001). Plant physiology: The ups and downs of guard cell signalling. Curr. Biol. 11: R92-R94 with permission from Elsevier; Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.
© 2014 American Society of Plant Biologists
Summary: Calcium • Much of a plant’s calcium may be in the form of calcium oxalate crystals • Free Ca2+ ion is mainly stored outside cytosol, in apoplast and vacuole • Calcium has a structural role in cell walls, particularly pectin gelling • Calcium has a signaling role conferred by transient spikes in cytosol
© 2014 American Society of Plant Biologists
Macronutrients: Summary • Macronutrients (N, P, K, S, Mg, Ca) are essential elements that must be acquired from the environment • Soil microbes affect nutrient availability and uptake • Nutrient-specific transporters control uptake, translocation and remobilization of mineral nutrients • Some macronutrients are assimilated into organic compounds • Uptake and assimilation reactions are coordinated by nutrient availability and demand • Replenishment of soil nutrients is essential for highyielding agricultural systems © 2014 American Society of Plant Biologists
Macronutrients - Summary
The ecological impacts of agriculture are huge and growing – most of these hypoxic regions arose since 1950 and are attributed to human activities Diaz, R.J. and Rosenberg, R. (2008). Spreading Dead Zones and Consequences for Marine Ecosystems. Science. 321: 926-929.
© 2014 American Society of Plant Biologists
Macronutrients - Summary WORLD POPULATION PROJECTION
9.6 billion (2050)
10.9 billion (2100)
Demand for food will not slow down during this century
7.2 billion (2012) We must find innovative solutions to the challenge of feeding the plants that feed us Gerland, P., Raftery, A.E., Ševčíková, H., Li, N., Gu, D., Spoorenberg, T., Alkema, L., Fosdick, B.K., Chunn, J., Lalic, N., Bay, G., Buettner, T., Heilig, G.K. and Wilmoth, J. (2014). World population stabilization unlikely this century. Science. 346: 234-237.
© 2014 American Society of Plant Biologists
Ongoing research: Learn how plants integrate different nutrient needs How do roots optimize growth when two or more nutrients are limiting? How can understanding this integration support breeding efforts? Interactive effects of nutrients and daylength on root growth
Cluster analysis of root traits that enhance acquisition of various nutrients
Kellermeier, F., Armengaud, P., Seditas, T.J., Danku, J., Salt, D.E. and Amtmann, A. (2014). Analysis of the root system architecture of Arabidopsis provides a quantitative readout of crosstalk between nutritional signals. Plant Cell. 26: 1480-1496. White, P.J., George, T.S., Dupuy, L.X., Karley, A.J., Valentine, T.A., Wiesel, L. and Wishart, J. (2013). Root traits for infertile soils. Front. Plant Sci. 4: 19.
© 2014 American Society of Plant Biologists
Ongoing research: Use best practices for nutrient management Manage nutrients properly, using the “4Rs” NH4NO3 or Urea?
How much?
Right
Right Before planting? During vegetative growth phase?
Right
Right
Between rows? On surface or deep?
Continue to develop technologies to ensure optimal fertilizer use, and make them affordable International Plant Nutrition Institute; See also American Society of Agronomy; Video link Plant Nutrition Institute
© 2014 American Society of Plant Biologists
