The Facts On File Dictionary of Botany

alkaloidreleased causes the dough to rise). Duringalcoholic fermentation acetaldehyde actsas a hydrogen acceptor instead of oxygen.The pyruvic acid formed by GLYCOLYSIS isbroken down into acetaldehyde and carbondioxide. The acetaldehyde is furtherreduced by NADH to form ethanal, releasingonly about a tenth of the energy thatwould be released by aerobic respiration.aldehyde A type of organic compoundwith the general formula RCHO, wherethe –CHO group (the aldehyde group) consistsof a carbonyl group attached to a hydrogenatom. Simple examples ofAldosealdehydes are methanal (formaldehyde,HCHO) and ethanal (acetaldehyde,CH 3 CHO).aldose A SUGAR containing an aldehyde(CHO) or potential aldehyde group. Examplesinclude the sugars ribose (with fivecarbon atoms) and glucose (with six carbonatoms).aleurone grain (aleurone body) A modifiedvacuole found in the embryo and endospermof seeds and containing mostlyreserve proteins, but also phytic acid andvarious enzymes associated with mobilization(digestion) of these reserves. The proteinsand phytic acid are present incrystalline form in the dormant seed.aleurone layer The outermost proteinrichlayer of the endosperm of grass fruits(e.g. cereal grains). At germination, the embryoproduces gibberellin, which stimulatesthe aleurone layer to synthesizeenzymes, especially amylase. The lattercauses hydrolysis of the starch in the endosperm.The enzymes are synthesizedfrom the amino acids supplied by breakdownof ALEURONE GRAINs.algae (sing. alga) A large mixed group ofphotosynthesizing eukaryotic organisms,now usually placed in the kingdom Protoctista.They often resemble plants and arefound mainly in marine or fresh-waterhabitats, although some algae are terrestrial.Algae differ from plants in lackingany real differentiation of leaves, stems,and roots, in having no layer of sterile cellsaround the reproductive organs,and in nothaving an embryo stage in their life cycle.Algae can be unicellular (e.g. Chlamydomonas),colonial (e.g. Volvox), filamentous(e.g. Spirogyra), or thalloid (e.g.Fucus). All algae contain chlorophyll butthis may be masked by various accessorypigments, these being one of the majorcharacteristics used to divide the algaeinto their various phyla. Other charactersused to classify the algae are the natureof storage products, the type of cell wall,the form and number of undulipodia(flagella), ultrastructural cell details, typeof food reserves, and reproductive processes.alkaline soilalkaloidSee calcareous soil.One of a group of organic com-9