The Physiology of Flowering Plants - KHAM PHA MOI

374 APPENDIXSI unitsPreviously employed unitsLengthBasic unit metre, mBasic unit metre, m1 mm, micrometre = 10 –6 m 1m, micron = 10 –6 m1 nm, nanometre = 10 –9 m 1mm, millimicron = 10 –9 mVolumeBasic unit cubic metre, m 3 Basic unit litre L (or l) = 10 –3 m 31dm 3 =10 –3 m 3 1 L = 1dm 31cm 3 =10 –6 m 3 1 mL, millilitre = 10 –3 L=1cm 31mm 3 =10 –9 m 3 1 mL microlitre = 10 –6 L=1mm 3EnergyBasic unit joule, JTemperatureBasic unit kelvin, K (formerly degrees Kelvin, 8K).1K=18C, but the kelvin scale starts at absolutezero, so that 0 K = –273 8C, and 0 8C = 273 KPressureBasic unit newton per square metre, N m –2 = thepascal, Pa (1 N = 1 kg m s –2 )kPa, kilopascal = 10 3 PaMPa, megapascal = 10 6 PaAmount of substanceMole (symbol mol), amount of substance of asystem which contains as many elementaryunits as there are carbon atoms in 0.012 kg ofcarbon-12. Can be applied to entities otherthan chemicals, e.g. used for ‘amount’ of light interms of photonsConcentrationMeasured in mol m –3 (or mol dm –3 ,molcm –3 etc.)Basic unit erg = 10 –7 J1 calorie, cal = 4.18 JDegrees centigrade (Celsius), 8CBar or atmosphere, atm1 bar = 10 5 Pa1 atm = 1.01325 10 5 PaGram-molecule (g-mole), the amount of acompound whose mass in g is equal to itsmolecular weight; numerically equals mole butonly applicable to chemical substancesMeasured in molarity, MA 1 M (molar) solution contains1 g-mole L –1 =10 3 mol m –3Avogadro’s numberThe number of elementary units per mole (or g-mole) = 6.02252 10 23 mol –1Mass of very small entitiesMasses of atoms, molecules and molecular aggregates are minute and therefore generally not measured inSI mass units, but given relative to each other; starting with a value of 1 for the lightest atom, H. One caneither say that the H atom has a relative molecular mass M r of 1, or that it has a mass of 1 dalton, Da.