Environmental Control of a Glasshouse Suite for Crop Physiology

Five commercial glasshouses, each with a floor area of 10 mx 5 m, are equipped for control of temperature, humidity, carbondioxide concentration and ventilation rate using a PDP 11 computer.Heating is provided by a hot-air gas-fired system with a fastresponse time and roof ventilators are mechanically operated.Humidity is increased by the injection of fine water droplets.The internal concentration of CO₂ is held close to the externalconcentration by the injection of pure CO₂ during the day. Air temperature is allowed to cycle in phase with the externaltemperature and an algorithm applies retrospective correctionswhich hold long-term mean temperatures within about 0.1 °C of set values. Control of saturation deficit is limited bythe vapour pressure of the external air and by the temperatureof the glasshouse walls. The dependence of crop photosynthesisrate on irradiance has been established from diurnal changesin the rate of CO₂ injection. Each glasshouse is large enough to allow regular harvestingof plants and the installation of tube solarimeters measuringlight interception, access tubes for neutron probes, tensiometersand auxanometers. The cost of the system was about £500per m², an order of magnitude less than figures quoted for conventionalgrowth cabinets and phytotrons. Key words: Environment, Computer control, Glasshouses     

The Hiletini, an ancient and enigmatic tribe of Carabidae with a pantropical distribution (Coleoptera)

Abstract. Species of the tribe Hiletini are rarely represented in collections. Of the twenty known species, only three have been adequately collected. These twenty species are here arrayed in two genera, Hiletus (six species in two spe'cies groups), Eucamaragnathus (fourteen species in five species groups). Hiletus species occur in tropical Africa. Eucamaragnathus species of the alluaudi group occur in tropical and southeastern Africa, those of the suberbiei group are found only in Madagascar, those of the bocandei group are found in tropical western Africa, species of the sumatrensis group occur in southeastern Asia (Burma, Vietnam, Sumatra and Borneo), and those of the batesi group are found in the western Amazon Basin, northeastern Amazon Basin, and along the Paraquay River drainage system. Four new species of Hiletini are described from the following type localities: Hiletus nimba, GUINEA, Nimba Mountains; Eucamaragnathus borneensis, BRUNEI, (BORNEO); E.jaws, BRAZIL, Parana; E.amapa, BRAZIL, Territory of Amapa. Most species of Hiletini live in tropical climates with a mean annual temperature above 21°C and mean annual rainfall above 200 cm (exceptions are noted in text). All species apparently frequent latosolic soils in broadleaf evergreen or deciduous forests or in grassland savannahs with scattered or gallery broadleaf evergreen trees. Records available indicate that pupation occurs during the dry season and that adults emerge with the onset of rains. The structure of the mandibles, other mouthparts, crop and proventriculus suggests that only liquid food is normally taken in, and it is probable that at least some preoral digestion occurs as in other carabids. A suite of newly discovered character states associated with the tarsal claws unites the Hiletini with Cnemacanthini, Elaphrini, Migadopini, Promecognathini, Pseudomor-phini, Scaritini and Siagonini. These stocks together form a sister lineage to the ozaenine-brachinine lineage, all having distinct epimera, brushy non-styliform parameres, long empodial unguitractor plates, but not having conjunct mesocoxae (type I). Hiletini is the sister group of the combined Scaritini-Cnemacanthini-Pseudomorphini stocks. We suggest that the origin of the Hiletini occurred at least as early as the Jurassic Period from an equatorial position near the centre of the combined Africa/South America landmass. By mid-Cretaceous, radiation of taxa occurred across southern Laurasia into the southeastern part of that landmass, but never leaving equatorial climates. Later in the Cretaceous or early Tertiary, when continents began their rapid break-up, hiletines were stranded in tropical parts of South America, Africa/Madagascar, and southeastern Asia where they still occur today.     

Devlopmental Physiology of Sugar-Beet: II. EFFECTS OF TEMPERATURE AND NITROGEN SUPPLY ON THE GROWTH, SOLUBLE CARBOHYDRATE CONTENT AND NITROGEN CONTENT OF LEAVES AND ROOTS

Plants were grown at temperatures of 15 and 25 ?C with two ratesof nitrogen supply. The changes in dry weight, leaf area, cellnumber, mean cell volume, soluble carbohydrate, and total nitrogenconcentration of the cotyledons, the first and second pair oftrue leaves, and the storage root were measured. Changes incell number and cell volume of the first pair of true leavesand storage root of plants were also measured at 11, 18, 25,and 32 ?C. Leaf growth before unfolding was chiefly by increase in cellnumber and after unfolding by increase in mean cell volume,while the growth of the storage root was almost entirely byincrease in cell number. The rates of cell division and cellexpansion were fastest at 25 ?C, but the initially high ratesof cell division in the terminal bud and in individual leavesdecreased rapidly and greater rates were maintained at the sub-optimaltemperatures, i.e. 15 and 18 ?C. After an initial period ofslow growth, the first-formed leaves grew faster and becamelarger at 15 than at 25 ?C. Leaves were produced, unfolded,grew faster, and became larger with increase in the externalconcentration of nitrogen, because cells divided and expandedfaster, so that nitrogen increased the number and size of cells. Sugar concentration was greater at 15 than at 25 ?C in leavesbut not in the storage root. Sugar concentration in the petiolesof the first and second pair of true leaves increased to 1.2and 2.0 per cent fresh weight respectively. Decreased nitrogensupply temporarily increased the sugar concentration of cotyledonpetioles and the seedling hypocotyl, but later decreased itin the leaves and storage root. Nitrogen concentration was greaterin the leaves and storage root at 15 than at 25 ?C with thelarger nitrogen supply. Nitrogen concentrations were similarin young leaves of all treatments but as the size of leavesincreased nitrogen concentrations decreased most rapidly at25 ?C with the smaller nitrogen supply. It is suggested that when increased leaf production and storage-rootgrowth occurs at temperatures below the growth optimum (25 ?C),they may be due to an effect of increased carbohydrate supplyon cell division and sugar storage.