Influence of Elevated CO2 and Temperature on the Photosynthesis and Respiration of White Clover Dependent on N2 Fixation

Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N₂ fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO₂, and temperature 23/18 °C day/night temperaturesat 680 µmol mol^–1 CO₂, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol^–1 CO₂ (C340)After 3–4 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO₂ and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 17–29%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO₂ mol H₂O^–1)was also significantly increased Plants acclimated to elevatedCO₂, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves ‘instantaneously’exposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO₂, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO₂ at 23 °C increased graduallyfrom approx 10 % at 100 µmol m^–1 s^–1 to >27 % at 1170 µmol m^–2 s^–1 In parallel, wateruse efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 In parallel,water use efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 to approx100 % at the highest irradiance Elevated CO₂, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO₂ and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N₂, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO₂, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO₂, elevated temperature, water use efficiency, N₂ fixation     

Growth of corn in saline waters

Eight cultivars of Zea mays plus the wild species Zea diploperennis were screened for seedling saline tolerance up to 3.2% NaCl. The best performances were given by the cultivars Mo 17 and commercial Hawaiian Super Sweet Hybrid. These two were then field grown on coral-cinder beds using drip irrigation with fresh of half-strength sea water (1.5–1.7% dissolved solids). Growth and chemical data for Mo 17 at 12 weeks show reduced growth but the same percentage dry matter. Ash, protein and total sulfur were higher in saline plants, silica and total phosphorus lower. Na, K. Mg, and Cl were elevated and Ca reduced slightly. Fe was also increased in saline plants. Both Mo 17 and Super Sweet Hybrid corn flowered and produced seed which retained essentially normal viability both in fresh and salt water.     

Some Metabolic and Biochemical Characteristics of Representative Microbial Isolates from Vacuum-packaged Beef

Some of the metabolic and biochemical characteristics of 105 organisms isolated at 4° from meat matured in vacuo at 0–2° for 0–9 weeks were studied. Proteolysis was noted in Pseudomonas spp., Achromobacter spp. and Gram negative, fermentative organisms, mainly in aerobic and low oxygen environments. Fewer organisms hydrolysed beef fat than hydrolysed tributyrin. While representatives of most of the major groups of organisms dissimilated mono- and di-saccharides, more complex carbohydrates were less readily attacked. Only Gram negative, fermentative organisms showed decarboxylase activity on amino acids. There is evidence that Pseudomonas spp. can survive in an anaerobic environment, although their metabolism is less vigorous.     

Regeneration and growth of coolibah,Eucalyptus coolabah subsp. arida,a riparian tree,in the Cooper Creek region of South Australia

Abstract Regeneration patterns of Eucalyptus coolabah Blakely & Jacobs subsp. arida (Blakely) L. Johnson & K. Hill (coolibah), a riparian tree of inland Australia, were inferred from size classes at two locations in South Australia; part of the floodplain of Cooper Creek and a swale in the Strzelecki Desert. These had contrasting water regimes; Cooper Creek floods on average once every 5–6 years whereas the swale has a continual water supply from a bore. A peak in size class distribution showed a regeneration event at each location but at different times. The one in the swale was more recent and was dated to the mid-1970s using aerial photography. Young (< 5 m tall) trees, interpreted as recent regeneration, were concentrated on specific topographic features, the top of a steep riverbank and a sand mound separate from the main dune system. Access to these features would have been difficult after flooding suggesting regeneration is dependent on protection from introduced herbivores. Field observations of reproductive status and canopy die-back showed coolibah condition was better in the swale. The relatively poorer condition of floodplain coolibahs was attributed to saline soils compounded by drier conditions rather than age.     

Changes in glucosinolates during crop development in single- and double-low genotypes of winter oilseed rape (Brassica napus): II. Profiles and tissue-water concentrations in vegetative tissues and developing pods

The concentrations of glucosinolates in the tissue water of leaves, stems, floral buds and developing pods were measured at defined stages of development in four oilseed rape cultivars known to have different seed glucosinolate concentrations (Bienvenu, Ariana, Cobra and Capricorn). Five alkenyl, two aromatic and three indolyl compounds were identified in the vegetative and reproductive organs. Substantial differences developed in the profiles of compounds present during vegetative growth. The 2-hydroxy-3-butenyl glucosinolate was primarily associated with developing and mature seeds and germinated seedlings. The 4-pentyl glucosinolate occurred mainly during the later stages of vegetative growth in spring, when leaves contained higher concentrations than stems, and during the early stages of flowering. The 2-phenylethyl and 3-indolymethyl glucosinolates were present earlier in vegetative growth when similar concentrations were present in leaves and stems. Differences between cultivars in the tissue-water concentrations of individual glucosinolates were small during vegetative growth. The leaves of Cobra and Capricorn had smaller concentrations of the 3-pentyl glucosinolate than Bienvenu and Ariana especially early in spring, and the stems of Capricorn had smaller concentration of the 3-pentyl and 2-phenylethyl glucosinolates. Greater differences between cultivars developed during pod growth and involved large increases in the concentrations of the 2-hydroxy-3-butenyl and 3-butenyl glucosinolates, especially in Bienvenu and Ariana. The implications of these changes in the types and concentrations of glucosinolates in the different organs for the incidence of pests and diseases are discussed.