Morphological Differentiation induced by Prostaglandin in Mouse Neuroblastoma Cells in Culture

PROSTAGLANDIN is known to affect concentrations of cyclic AMP in some cells¹. Dibutyryl cyclic AMP induces irreversible differentiation of mouse neuroblastoma cells in vitro², which raises the question of whether prostaglandin would mimic this effect. I report here that prostaglandins (PG)E₁ and PGE₂ induce irreversible morphological differentiation of mouse neuroblastoma cells in culture as shown by axon formation, whereas PGF₂α does not.     

Response of in vitro pollen germination and pollen tube growth of groundnut (Arachis hypogaea L.) genotypes to temperature

Air temperatures of greater than 35 °C are frequently encountered in groundnut‐growing regions, especially in the semi‐arid tropics. Such extreme temperatures are likely to increase in frequency under future predicted climates. High air temperatures result in failure of peg and pod set due to lower pollen viability. The response of pollen germination and pollen tube growth to temperature was quantified in order to identify differences in pollen tolerance to temperature among 21 groundnut genotypes. Plants were grown from sowing to harvest in a poly‐tunnel under an optimum temperature of 28/22 °C (day/night). Pollen was collected at anther dehiscence and was exposed to temperatures from 10° to 47·5 °C at 2·5 °C intervals. The results showed that a modified bilinear model most accurately described the response to temperature of percentage pollen germination and maximum pollen tube length. Genotypes were found to range from most tolerant to most susceptible based on both pollen characters and membrane thermostability. Mean cardinal temperatures (T_min, T_opt and T_max) averaged over 21 genotypes were 14·1, 30·1 and 43·0 °C for percentage pollen germination and 14·6, 34·4 and 43·4 °C for maximum pollen tube length. The genotypes 55‐437, ICG 1236, TMV 2 and ICGS 11 can be grouped as tolerant to high temperature and genotypes Kadiri 3, ICGV 92116 and ICGV 92118 as susceptible genotypes, based on the cardinal temperatures. The principal component analysis identified maximum percentage pollen germination and pollen tube length of the genotypes, and T_max for the two processes as the most important pollen parameters in describing a genotypic tolerance to high temperature. The T_min and T_opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating genotypes for high temperature tolerance. Genotypic differences in heat tolerance‐based on pollen response were poorly related (R² = 0·334, P = 0·006) to relative injury as determined by membrane thermostability.     

Stomatal responses to changes in vapor pressure deficit reflect tissue‐specific differences in hydraulic conductance

The vapor pressure deficit (D) of the atmosphere can negatively affect plant growth as plants reduce stomatal conductance to water vapor (g_wv) in response to increasing D, limiting the ability of plants to assimilate carbon. The sensitivity of g_wv to changes in D varies among species and has been correlated with the hydraulic conductance of leaves (K_leaf), but the hydraulic conductance of other tissues has also been implicated in plant responses to changing D. Among the 19 grass species, we found that K_leaf was correlated with the hydraulic conductance of large longitudinal veins (K_lv, r² = 0.81), but was not related to K_root (r² = 0.01). Stomatal sensitivity to D was correlated with K_leaf relative to total leaf area (r² = 0.50), and did not differ between C₃ and C₄ species. Transpiration (E) increased in response to D, but 8 of the 19 plants showed a decline in E at high D, indicative of an ‘apparent feedforward’ response. For these individuals, E began to decline at lower values of D in plants with low K_root (r² = 0.72). These results show the significance of both leaf and root hydraulic conductance as drivers of plant responses to evaporative demand.     

The Responses of White Spruce and Yellow Birch to Some Selected Organophosphorus Insecticides and the Adjuvants Atlox and Arotex

At concentrations of 10 and 100 parts 10^–6 the insecticidesfenitrothion, acephate (Orthene^?), and phosphamidon inhibitedsome germination characteristics of white spruce seeds. Thelevel of inhibition was dependent upon the applied pesticideconcentration. By contrast, at these concentrations acephateand phosphamidon enhanced germination of yellow birch seeds,while 10 parts 10^–6 fenitrothion slightly stimulated germination.Higher concentrations of fenitrothion (25–50 and 100 parts10^–6) seriously depressed the germination of yellow birchseeds. Gross morpho-genetic changes and lack of seedling vigourcharacterized the growth of seedlings exposed to the higherconcentrations of fenitrothion. The metabolite S-methylfenitrothiondecreased germination of yellow birch seeds at concentrationsof 10 or 100 parts 10^–6; however, the emergent seedlingsgrew normally and did not show any dwarfing effects.     

Alleviation by Gibberellic Acid and Kinetin of the Inhibition of Seed Germination in Maize (Zea mays L.) under Submerged Conditions

Under submerged conditions the germination of maize seeds isinhibited. Under normal conditions, i.e. on moist filter paper,more than 80 per cent of the seeds can germinate whereas lessthan 24 per cent of the seeds germinate under submerged conditions.The inhibition of germination under submerged conditions canbe fully overcome by the application of an appropriate concentrationof GA₂, and KN. The possible role of these hormones in overcomingthe inhibition of seed germination under an oxygen deficit dueto waterlogging is discussed. Zea mays L, maize, gibberellic acid, kinetin, germination     

Solute accumulation, solute potential, germinability and seedling vigour of seeds of finger millet (Eleusine coracana Gaertn.) raised under rain-fed conditions and under irrigation

Abstract The nature of the solutes accumulated in the grains of ten finger millet genotypes grown under rain-fed conditions with moisture stress during panicle and grain development were determined. Although grain yield decreased under stress, the solute potential (SP) of seeds from stressed plants was significantly lower (more negative), probably due to the increase in sucrose content. There were no significant changes in the content of total amino acids, free proline, reducing sugars or potassium. The contribution of sucrose to total solute potential was approximately 32% in seeds obtained from stressed plants as compared with only 15% in seeds from irrigated treatment. The germinability and seedling vigour of the seeds from stressed plants was significantly higher under simulated stress with polyethylene glycol (PEG), but was similar to that of seeds of non-stressed plants under normal conditions.     

Genotypic Variability in Differential Expression of lea2 and lea3 Genes and Proteins in Response to Salinity Stress in Fingermillet (Eleusine coracanaGaertn) and Rice (Oryza sativaL.) Seedlings

Some late embryogeny abundant (LEA) proteins, which are developmentallyregulated in embryos, are also known to be expressed in meophytictissues in response to osmotic stress. Here we report the extentof genetic variability in the level of expression of lea2 andlea3, under stress, in fingermillet and rice seedlings. In bothspecies, the expression of lea genes was seen in the mesophytictissue in response to salinity, partial dehydration and abscisicacid. Tolerant genotypes exhibited higher expression of rab16Aand M3 that code for LEA2 proteins, than susceptible genotypes.A novel approach, that of raising antibodies against the conservedpeptides of these proteins was used to study genetic variabilityin LEA protein levels. Since stress proteins are known to beexpressed in response to mild, non-lethal induction-stress (Uma,Prasad and Udayakumar,Annals of Botany76: 43–49, 1995),we developed an optimum induction protocol for salinity stressin rice and fingermillet. We studied the quantitative differencesin expression of these proteins by western blot and ELISA techniquesin different genotypes. A positive correlation was found betweenLEA2 and LEA3 protein levels and the growth of seedlings duringstress and recovery in both rice and fingermillet, indicatinga possible relevance of these proteins in stress tolerance.Copyright1998 Annals of Botany Company LEA proteins, ABA responsive proteins, induction response, ELISA, fingermillet, rice, salinity-stress.