Inhibition of Germination in Kochia indica

Seeds of Kochia indica Wight germinate rapidly in shallow water,but their germination is retarded on moist filter-paper. Theretardation is traced to a surface-active, saponin-like inhibitor,which is readily leached away in water and is adsorbed by charcoalor soil. Excised embryos may also remain dormant on filter-paper,but if rinsed in water quickly become active. Inhibition isfavoured by higher temperature (30°C. as against 20°or less), especially in an atmosphere of oxygen, although onceactive the embryos grow rapidly in such conditions. When theoxygen concentration is reduced to 5 per cent., germinationand growth are markedly retarded, but 5 per cent. CO₂ has littleor no retarding effect.     

Trait–environment relations for dominant grasses in South African mesic grassland support a general leaf economic model

Question: Following the framework of Suding et al. (2003), we examined whether morphological traits (organismal response), tolerance and competitive effect (specific process response) were associated with grass dominance (abundance response) on burning, mowing, fertilization and soil depth gradients in KwaZulu‐Natal (KZN), South Africa. Location: University of KwaZulu‐Natal, Pietermaritzburg, South Africa. Methods: Using several pot experiments involving 29 grass species in total, we determined the vegetative traits, competitive effect and response, and tolerance to shading for grasses common in closed, tufted mesic grassland in KZN. Results: The primary axis of grass–trait variation was most strongly related to a negative correlation (trade‐off) between growth rate and specific leaf area (SLA), with broad‐leaved, rapidly‐growing grasses (high SLA) occupying one extreme and narrow‐leaved, slow‐growing grasses (low SLA) the other extreme of the first principal component. The low SLA, slow‐growth strategy was found to be a relatively general strategy among grasses dominant in undisturbed, high litter grassland, as well as those adapted to moisture‐stressed habitats. In contrast, grasses dominant in highly productive habitats with some form of disturbance, e.g. mowing, had a broad‐leaved, rapid‐growth strategy. Intermediate combinations of the SLA–growth rate trade‐off were common among grasses dominant under other combinations of disturbance and soil resource availability. Conclusions: Distinct patterns of organismal (SLA, growth rate) and specific process (competitive effect and response, as well as tolerance of shading) responses appeared to be associated with grasses dominant on gradients of burning, mowing, fertilization and soil depth. These organismal and specific process responses were similar to those for North American and European grasses dominant under the same environmental influences, suggesting that some general trait–environment patterns exist at an inter‐continental scale. This general trait–environment relationship appears to be driven by functional adaptive selection along the SLA–environment continuum and its unavoidable trade‐off with growth rate.     

Phenotypic and Molecular Assessment of Wheat Genotypes Tolerant to Leaf Blight,Rust and Blast Diseases

Globally among biotic stresses, diseases like blight, rust and blast constitute prime constraints for reducing wheat productivity especially in Bangladesh. For sustainable productivity, the development of disease-resistant lines and high yielding varieties is vital and necessary. This study was conducted using 122 advanced breeding lines of wheat including 21 varieties developed by Bangladesh Wheat and Maize Research Institute (BAMRI) with aims to identify genotypes having high yield potential and resistance to leaf blight, leaf rust and blast diseases. These genotypes were evaluated for resistance against leaf blight and leaf rust at Dinajpur and wheat blast at Jashore under field condition. Out of 122 genotypes tested, 20 lines were selected as resistant to leaf blight based on the area under the diseases progress curve (AUDPC) under both irrigated timely sown (ITS) and irrigated late sown (ILS) conditions. Forty-two genotypes were found completely free from leaf rust infection, 59 genotypes were identified as resistant, and 13 genotypes were identified as moderately resistant to leaf rust. Eighteen genotypes were immune against wheat blast, 42 genotypes were categorized as resistant, and 26 genotypes were identified as moderately resistant to wheat blast. Molecular data revealed that the 16 genotypes showed a positive 2NS segment among the 18 immune genotypes selected against wheat blast under field conditions. The genotypes BAW 1322, BAW 1295, and BAW 1203 can be used as earlier maturing genotypes and the genotypes BAW 1372, BAW 1373, BAW 1297 and BAW 1364 can be used for lodging tolerant due to short plant height. The genotypes WMRI Gom 1, BAW 1349 and BAW 1350 can be selected for bold grain and the genotypes WMRI Gom 1, BAW 1297, BAW 1377 can be used as high yielder for optimum seeding condition but genotypes BAW 1377 and BAW 1366 can be used for late sown condition. The selected resistant genotypes against specific diseases can be used in the further breeding program to develop wheat varieties having higher disease resistance and yield potential.     

Spontaneous activity in the developing mouse midbrain driven by an external pacemaker

Central nervous system (CNS) development depends upon spontaneous activity (SA) to establish networks. We have discovered that the mouse midbrain has SA expressed most robustly at embryonic day (E) 12.5. SA propagation in the midbrain originates in midline serotonergic cell bodies contained within the adjacent hindbrain and then passes through the isthmus along ventral midline serotonergic axons. Once within the midbrain, the wave bifurcates laterally along the isthmic border and then propagates rostrally. Along this trajectory, it is carried by a combination of GABAergic and cholinergic neurons. Removing the hindbrain eliminates SA in the midbrain. Thus, SA in the embryonic midbrain arises from a single identified pacemaker in a separate brain structure, which drives SA waves across both regions of the developing CNS. The midbrain can self‐initiate activity upon removal of the hindbrain, but only with pharmacological manipulations that increase excitability. Under these conditions, new initiation foci within the midbrain become active. Anatomical analysis of the development of the serotonergic axons that carry SA from the hindbrain to the midbrain indicates that their increasing elongation during development may control the onset of SA in the midbrain. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009     

The tobacco Ntann12 gene, encoding an annexin, is induced upon Rhodoccocus fascians infection and during leafy gall development

Annexins are calcium-binding proteins that have been associated in plants with different biological processes such as responses to abiotic stress and early nodulation stages. Until now, the implication of annexins during plant–pathogen interactions has not been reported. Here, a novel plant annexin gene induced in tobacco BY-2 cell suspension cultures infected with the phytopathogenic bacterium Rhodococcus fascians (strain D188) has been identified . Expression of this gene, called Ntann12 , is also induced, but to a lower extent, by a strain (D188-5) that is unable to induce leafy gall formation. This gene was also induced in BY-2 cells infected with Pseudomonas syringae but not in cells infected with Agrobacterium tumefaciens or Escherichia coli. Ntann12 expression was also found to be stimulated by abiotic stress, including NaCl and abscissic acid, confirming a putative role in stress signal transduction pathways. In addition, promoter- GUS analyses using homozygous transgenic tobacco seedlings showed that the developmentally controlled expression of Ntann12 is altered upon R. fascians infection. Finally, up-regulation of Ntann12 during leafy gall ontogenesis was confirmed by RT-qPCR. Discussion is focused on the potential role of Ntann12 in biotic and abiotic stress responses and in plant development, both processes that may involve Ca²⁺-dependent signalling.