Effects Of Supraoptimal Temperatures Research Articles

The effect of bacterial-based biofertilisers and cytokinin on the emergence of sunflower at non-limiting and supra-optimal temperatures

Subsurface sunflower (Helianthus annuus L.) seedling growth often deteriorates on sandy-textured soils due to supra-optimal temperature levels on the Highveld area of South Africa leading to poor emergence and suboptimum plant population densities. It has been shown that seedling growth is enhanced by the application of plant growth promoting rhizobacteria and cytokinin. The possibility therefore exists that the poor emergence problem might be remedied through the use of these applicants. The objective of this investigation was to determine if commercially available bacterial-based biofertilisers and cytokinin can enhance the seedling vigour of subsurface sunflower seedlings in controlled ambient temperatures ranging from non-limiting to supra-optimal and in unregulated field conditions. The results suggest that there are conditions where bacterial-based biofertiliser and cytokinin can alleviate the damaging effect of supra-optimal temperatures on the emergence of sunflower. However, the effect of these applicants on various cultivars and soil conditions require further investigation.

Temperature sensitivity of herpes simplex virus type 1 is a tissue-dependent phenomenon.

The temperature sensitivity of herpes simplex virus type 1 (HSV-1) was assessed in primary cultures of mouse central nervous system (MNS) cells and mouse embryo cells (MEC). Infectious yields were determined and the ultrastructural morphogenesis of HSV-1 particles was compared following incubation at 37 or 40.5 degrees C. Yields of infectious virus were significantly reduced for both types of cell cultures following incubation at 40.5 degrees C. However, the effect of supraoptimal temperature (40.5 degrees C) on HSV-1 replication in MEC was significantly greater than the effect of supraoptimal temperature on virus replication in MNS cells. With respect to viral morphogenesis, no significant differences were found in either the quantity or the appearance (empty versus electron opaque core) of intranuclear particles present per infected nucleus, regardless of cell type or incubation temperature. However, complete virus particles (enveloped capsids with dense cores) were never observed in MEC at 40.5 degrees C, either intracytoplasmically or extracellularly. In contrast, complete virus particles were observed in MNS cell cultures at 40.5 degrees C, albeit in reduced numbers. At the permissive temperature (37 degrees C), complete intracytoplasmic and/or extracellular virus particles were associated with every infected cell in the MNS cell or MEC cultures. Thus an interactional effect on HSV-1 replication was found between cell culture type and incubation temperature.

Ethylene Production and 1-Aminocyclopropane-1-Carboxylic Acid Conjugation in Thermoinhibited Cicer arietinum L. Seeds

The effect of supraoptimal temperatures (30 degrees C, 35 degrees C) on germination and ethylene production of Cicer arietinum (chick-pea) seeds was measured. Compared with a 25 degrees C control, these temperatures inhibited both germination and ethylene production. The effect of supraoptimal temperatures could be alleviated by treating the seeds with ethylene. It was concluded that one effect of high temperature on germination was due to its negative effect on ethylene production. This inhibitory effect of high temperature was due to increased conjugation of 1-aminocyclopropane-1-carboxylic acid to 1-(malonylamino)cyclopropane-1-carboxylic acid and to an inhibition of ethylene-forming enzyme activity.

The effects of supraoptimal temperatures upon North American brown-rot fungi in pure culture

Ninety-one North American brown-rot fungi were exposed in agar culture to four high temperatures for 16 days. Isolates originated from basidiospores, sporophore tissue, or decaying wood. One or more isolates of 58 species grew at 35 °C, of 20 species at 41 °C, and of 4 species at 46 °C; none grew at 52 °C. Similar inter- and intra-specific variations occurred during recoveries in the absence of growth. Some isolates of two species of Antrodia recovered after exposure to 52 °C. The possibility that a brown rotter might be active, alive but inactive, or neither within a wood substrate can be inferred by comparison of ratings derived by mathematical formulae applied to species represented by four or more isolates. Species that destroy wood products made up 73% of those likely to grow at these higher temperatures and 81% of those most likely to recover from exposure to supramaximal temperatures based upon these ratings. Only 2 of the 12 fungi least capable of growth and recovery at high temperatures were associated with forest products. Temperature ratings for two fungi that had been isolated by another worker from western pine slash coincided with the upper and lower portions in which they occurred. However, field data were insufficient for a satisfactory comparison of sapwood and heartwood rotters.

Effect of supraoptimal temperatures upon tobacco mosaic virus RNA replicase.

An examination of the effect of supraoptimal temperatures upon tobacco mosaic virus (TMV) RNA replicase demonstrated that the enzyme activity rapidly decreased at 40 degrees whether incubated in vitro after extraction or in leaves at that temperature prior to extraction and assay. The loss of replicase activity paralled the decline in capacity for in vivo incorporation of 32P into TMV RNA at 25 degrees following different periods of incubation at 40 degrews. The optimal temperature for replicase activity in vitro 35 degrees, and greater activity occurred at 40 than at 25 degrees. After about 15 min incubation at 40 degrees, in vivo incorporation of 32P into double-stranded TMV RNA became temperature-sensitive. This function could not be reproduced with the in vitro replicase system.

The effect of heat treatment on the damage and recovery of the protein synthesis mechanism of human kidney cell line.

The effect of supraoptimal temperature on the suppression and recovery of protein synthesis activity in cultures of human kidney cell line was studied. It was shown that 44 degrees C is a critical temperature to these cells, and after exposure to this temperature for 3 hours no recovery of protein synthesis activity could be detected. The cloning efficiency of cells exposed to 44 degrees C for 2 hours was irreversibly reduced to zero. Protein synthesis at 43 degrees C was much less affected, showing considerable recovery after eight hours exposure. Differences in heat susceptibility of individual cells in the culture were observed, but the reason for this heterogeneity is not yet known.

The effect of heat treatment on glucose metabolism in human kidney cell line.

The effect of supraoptimal temperature on various glucose metabolism pathways of human kidney cell line was studied. Exposure of cells to 44 degrees C for longer than one hour resulted in decreased activity of the tri-carboxylic-acid (Krebs) cycle, which hardly recovered at 72 hours. The first few steps of the pentose phosphate pathway were found to be much less sensitive to heat treatment than the whole cycle, and continued to be partially active even after a 3-hour exposure to 48 degrees C.

The Effect of Supraoptimal Temperatures on the Fine Structure of Merulius lacrymans (Jacq.) Fr.

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The relationship between deoxyribonucleic acid replication and cell division in heat-synchronized tetrahymena.

The effect of supraoptimal temperature on macronuclear DNA synthesis in Tetrahymena was studied by radioautography during prolonged heat and heat-shock synchronization treatments. Prolonged heat treatments (34 degrees C) delayed the initiation of S, but did not appreciably delay DNA synthesis in progress. Return to optimal temperature (28 degrees C) 50 or 100 min later resulted in initiation of S, in delayed cells, at a rate greater than in controls. During the synchronization treatment, most cells were unable to enter S during a heat shock, but initiated S with a slight delay during the following intershock period. These cells were not appreciably delayed in completion of S by subsequent heat shocks. Supraoptimal temperature appears to affect the DNA synthetic cycle near the G(1) to S transition. Cells subjected to the heat-shock treatment in early G(1) all participated in one S period, and many underwent a succession of two S periods. DNA synthesis occurred in about 50% of the cells between EST and the first synchronous division, with the likelihood of DNA synthesis becoming greater the longer the interval between these two events. In some cells no detectable DNA synthesis occurred between EST and the second synchronous division. It was concluded that a precise temporal alternation of DNA replication and cell division is not obligatory in Tetrahymena.

The effect of supraoptimal temperatures on the contents of krebs' cycle acids in Arabidopsis thaliana

The effect of supraoptimal temperatures on the contents of several Kreb's cycle acids in Arabidopsis thaliana (L.) Heynh was investigated. Plants grown at the higher temperatures (32° day and 25° night) were lower in dry and fresh weights than those grown at the optimal temperatures (25° day and 18° night). Citric, succinic, fumaric, and malic acid concentrations were measured at 2, 3 and 4 weeks after planting. Although the sum of the amounts of the four acids was generally higher in the shoots of plants grown at supraoptimal temperatures than in those grown at optimal temperatures, at 3 weeks after planting, the reverse was true. This latter result was due largely to changes in the fumaric and malic acid contents. From the second to the third week of growth, the contents of these two acids dropped in higher temperature plants and rose sharply in the optimal temperature plants with an exactly opposite trend occurring from the third to fourth weeks of growth. In the fourth week, the citric acid content decreased to a very low value under optimal conditions and increased under supraoptimal conditions. The results show that malic and succinic acids are strikingly different with respect to compartmentation or to the directness of their association with the Krebs' cycle. The data provide information on changes in organic acid content in shoots through most of the life cycle of a plant, and they further show that temperature can affect organic acid levels at any given time.