Light detection system in higher plant chloroplasts: Pigment mediated or overall photon flux density related

Plants adapt to short term changes in irradiance and quality of the light environment by modulating the structure of the thylakoid membranes to make the best use of the available light energy. Shade-acclimated chloroplasts develop more thylakoid surface area as compared to those growing in full sunlight. Conversion of sun-type chloroplasts to shade-types and vice versa on the basis of total thylakoid membrane surface area can occur quickly. However, the response mechanism of chloroplasts to changes in light levels is yet to be understood. This short term light detection mechanism may be mediated by a pigment system other than photosynthetic pigments or it may be regulated by change in overall photon flux density. In order to verify the light detection mechanism, short term shade-acclimated sunflower chloroplasts were exposed for 4h to low irradiance white light supplemented with one part of the visible spectrum (blue, red, or yellow-green) enhanced up to sun irradiance. The main purpose of the treatment was to induce sun response in shade-acclimated chloroplasts. At the end the treatment period, leaf samples were taken for stereological analysis. Percent volume of chloroplasts and starch grains, actual volumes of palisade cells, chloroplasts, starch, and vacuoles, surface to volume ratio and actual surface area of stromal and granal thylakoid membranes were compared between control and treatment groups. The blue and yellow-green light treatment showed the most reduction in granal thylakoid surface area among the three treatment groups. The stromal thylakoid surface area, actual volume of chloroplasts, starch grains, palisade cells and vacuoles apparently did not respond to the treatment. The photosynthetic rate, relative quantum efficiency, and chlorophyll content did not change in response to short term change in light quality. The stereological data suggested that the light detection system in higher plant chloroplasts is probably regulated by a pigment system and the overall photon flux density incident on the chloroplasts is also critical. The presence of a different pigment system other than the photosynthetic pigments is yet to be established

Relations of Cercospora beticola with Host Plants and Fungal Antagonists

Cerco pora leaf pot (CLS) cau ed by Cercospora beticola Sacc., is sti ll considered to be the mo t important foliar di ease of ugar beel. The di ea e ha been reported wherever ugar beet i grO\\ n (Bieiholder and Weltzien 1972). Since the di ease wa fir t identified. management of CLS of ugar beet has been an ongoing mi ion of plant pathologists. Toda}. everal trategie are available and applied either s ingly or in combination to manage the di ea e. The e management trategie , which were ummarized by Windels et al. (1998), include cultural practice uch a deep tillage, rotation with non-host crops and identification and elimination of econdary weed host . Other include breeding and use of re i.tant cultivars and application of fungicide. The u e of re i tant sugar beet cultivars has long been an integral pan of CLS management; however, problems associated with selection of re i tant cuhivars again t CLS are wel l documented and were recently reviewed by Weiland and Koch (2004). According to the author , resistance to CLS in sugar beet has been de cribed as quantitatively in herited and rate limiting with respect to disease development (Smith and Gaskill 1970, Ro i et a l. 1999). Although resistant cultivars have proven effective in both North America and Europe, they nonetheless exhibit low heritability (Smith and Ruppel 1974), and cultivar bred for Cercospora resistance can still exhibit leaf pots if climatic condition favorable for the disease occur

Controlled Assembly of Rodlike Viruses with Polymers

A practical method to assemble rodlike tobacco mosaic virus and bacteriophage M13 with polymers was developed, which afforded a 3D core–shell composite with morphological control

Electrospinning Fabrication, Structural and Mechanical Characterization of Rod-Like Virus-Based Composite Nanofibers

Tobacco mosaic virus (TMV) was electrospun with polyvinyl alcohol (PVA) into continuous TMV–PVA composite nanofibers to form a biodegradable nonwoven fibrous mat as an extracellular matrix (ECM) mimetic. Morphological characterizations by electron microscopyshowed that the addition of varying amounts of TMV resulted in homogeneous nanofibers without phase separation and did not change the diameter of the composite nanofibers. The orientation of TMV in as-spun fibers could be readily controlled and post-processing of the nonwoven TMV–PVA mat significantly improved its water resistance. In addition, tensile tests were performed on individual nanofibers, which revealed that the TMV–PVA composite nanofibers achieved a comparable Young\u27s modulus as PVA nanofibers. Since the modification of TMV is readily achieved via genetic or chemical methods, this process offers a facile way to incorporate a variety of functionalities into polymer nanofibers. As a demonstration of its potential as ECM mimetic, a mutant TMV containing RGD peptide was co-spun with PVA and the resulting fibrous substrates were used to promote cell growth