The Physiology of Flowering Plants - KHAM PHA MOI

102 MINERAL NUTRITIONTable 4.1 Macronutrients, micronutrients and beneficial elements for flowering plants, and the main forms inwhich they are obtained. An asterisk* marks elements so far found to be essential only in some species; of these,silicon, chlorine and sodium are beneficial in numerous other species. Additional beneficial species are listed at theend of the table. Nitrate is the main N source. Of the three types of phosphate, the most important P source for plantsis H 2 PO – 4 ; all three phosphates can be referred to as Pi, inorganic phosphate, especially when it is uncertain whichion(s) is/are involved.Element Symbol Form absorbedEssential macronutrientsCarbon C CO 2 ,CO 2– 3 (carbonate), HCO – 3 (bicarbonate)Hydrogen H H 2 OOxygen O O 2 ,H 2 O, CO 2Nitrogen N NO – 3 (nitrate), NH + 4 (ammonium)Sulphur S SO 2– 4 (sulphate)Phosphorus P H 2 PO – 4 , HPO 2– 4 ,PO 3– 4 (phosphates)Calcium Ca Ca 2+Potassium K K +*Silicon Si H 4 SiO 4 (silicic acid)Essential micronutrientsIron Fe Fe 2+ (ferrous)Magnesium Mg Mg 2+Manganese Mn Mn 2+Copper Cu Cu 2+ (cupric)Zinc Zn Zn 2+Boron B H 3 BO 3 (boric acid)Nickel Ni Ni 2+*Cobalt Co Co 2+*Molybdenum Mo MoO 2– 4 (molybdate)*Chlorine Cl Cl – (chloride)*Sodium Na Na +Beneficial elementsSelenium Se SeO 2– 4 (selenate)Rubidium Rb Rb +Strontium Sr Sr 2+Aluminium Al Al 3+contain oxygen as well; these three elements are present in thegreatest amounts.Nitrogen, too, is a constituent of many cellular molecules, inparticular proteins and nucleic acids, the key macromolecules of lifeas we know it. There are many lower molecular weight nitrogenousorganic compounds vital to cell metabolism – vitamins, cofactors,hormones, the chlorophyll pigments and the phytochrome photoreceptors.Flowering plants additionally contain an extraordinaryvariety of nitrogenous secondary compounds not involved in basicmetabolism. These include alkaloids, among which are compounds