Studies ofribulose-1,5-bisphosphate (RuBP) carboxylase from taxonomically diverse plants show that the enzyme from Cs and crassuacean acid metabolism pathway species exhibits lower Km(CO2) values (12-25 micromolar) than does that from C4 species (28-34 micromolar ground in a mortar with 100 mm Bicine buffer (pH 8.0) containing 25 mm MgCl2 and 1 mm DTT (about 4-10 ml). The homogenate was centrifuged at 25,000g for 15 min, and 0.5 ml of the supernatant was eluted through a 0.8 x 15 cm column of Sephadex G-25, equilibrated in the same buffer. The void volume which contained RuBP carboxylase was collected and saved. The partially purified enzyme extract (1.0 ml) was preactivated in 5 mm NaHCO3, and then assayed by measuring the fixation of ["C]-bicarbonate. The reaction mixture containing 100 mm Bicine and 25 mm MgCl2 (pH 8.0) was prepared C02-free, and flushed with N2 prior to using it. Assays (total volume of400 ,ul) were performed in l-ml stoppered vials (Pierce Reacti-vials No. 13221) which had been flushed with N2. For Km(CO2) determination, the HCO3 concentration ranged from 0.4 to 16.5 mM, with RuBP fixed at 0.5 mM; and for Km(RuBP) determination, the RuBP concentration ranged from 7.5 to 500,iM, with HCO3 fixed at 10.6 mm. Reaction was started by injection of fully activated enzyme (5 ,ld for Km [COu] assays; 2-40 ,ul for Km[RuBP] assays), and stopped after 1 min at 25 C by injection of 0.2 ml 2 N HCOOH. The reaction mixture was then quantitatively transferred to a glass scintillation vial and evaporated to dryness on a hot plate. After the vial had cooled, 1.0 ml distilled H20 was added, followed by a 9.0-ml mixture of 5 g PPO in 1 liter toluene plus 500 ml Triton X-100. Each vial was then counted for 5 min in a Searle Delta 300 liquid scintillation counter. The bicarbonate introduced into the assay solution with the enzyme aliquot was taken into consideration when calculating HCO3 concentration and specific radioactivity. The CO2 concentration was calculated from the pH and HCO3 concentration using the Henderson-Hasselbach equation and pK' value of 6.37 at 25 C (16). The Km values were statistically calculated using

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A database containing automated descriptions of the angiosperm families, organised under the DELTA system, is described and illustrated with reference to its present capabilities and its potential. All 558 families are described in terms of certain basic information, including synonyms, geographical distributions, numbers of species and genera and classification according to four recent, influential classifications. Data on certain features have been widely or extensively incorporated (for example, with comprehensive coverage of variation in photosynthetic pathways, including source references); and 320 families (including all those represented in Australia) are described in sufficient morphological detail for multiple-entry, interactive identification. The interactive identification/information retrieval package is available in a form suitable for MS-DOS microcomputers.

Transections of leaf blades from 46 C4 grass species of known C4 type were recorded for presence (XyMS+) or absence (XyMS-) of cells intervening between metaxylem vessel elements and laterally adjacent chlorenchymatous bundle sheath cells of primary lateral vascular bundles. A perfect correlation, only 'NADP-ME type' species being XyMS-, indicated that XyMS type serves as a useful predictor of C4 species type. The likely C4 type of 255 biochemically-untyped grass species was accordingly deduced by direct observation (94 spp.) or from Metcalf's anatomical descriptions (161 spp.). All 124 C4 species examined, including C3 eu-panicoids, proved to be XyMS+.

A comprehensive world classification of the Poaceae is presented in which 720 currently accepted genera are distributed among five subfamilies (Pooideae, Bambusoideae, Arundinoideae, Chloridoideae, Panicoideae) and six supertribes (Triticanae and Poanae, in Pooideae; Bambusanae and Oryzanae, in Bambusoideae; Panicanae and Andropogonanae, in Panicoideae). Synonyms in recent use are listed under appropriate groups. The classification reflects a variety of numerical analyses of generic descriptions, accounting for original observations and compiled data on nearly 300 characters concerning mainly morphology, anatomy, physiology and cytology. The detailed group descriptions are fully comparative, and include statistical information on character state distributions. * Vulpiella (Trabut) Burollet, Wangenheimia Moench, Zingeria Smirnow Classification of the Poaceae Synonyms Anachortus V . Jirr.