SUMMARYLeaf senescetYce was analyzed in stay-green mutants of Phaseolus vulgaris. Impaired yellowing in these genotypes was accompanied by abnormal retention of tbylakoid membrane proteins including tbe ligbt-bar\'esting cblorophyll-binding protein of photosystem II, tbe 33 kDa polypeptide of tbe oxygen-evolving complex, cytocbrome/ and tbe psaF protein of pbotosystem I. On tbe other band, ribulose bispbospbate carboxylase was somewbat more labile in tbe mutant than tbe wild-type. Tbe stay-green cbaracter was not associated with unusual persistence of cbloropbyll biosynthesis etizymes. During senescence, normal leaf tissue accunnulated an array of fluorescent (FCC) and non-fluorescent (NCC) compounds witb cbromatograpbic and spectropbotometric properties similar to tbose of cbloropbyll catabolites previously identified in otber species. Witb the exception of one prominent NCC and a trace of one FCC, tbese constituents were absent from extracts of stay-green genotypes, strongly supporting tbe proposal tbat tbey are indeed products of cbloropbyll breakdown. Tbe kinetics of tbeir accumulation during senescence was consistent witb a primary or intermediary role for FCCs in tbe catabolic pathway wbereas NCCs seem to be final products. Tbe complement of FCCs and NCCs in Phaseolus vulgaris was as distinct from that of tbe previously-studied species barley and rape as tbe latter are from each otber. Genotj'pic and interspecific variations in tbe biochemistry of senescence are discussed in relation to genetic regulation of tbe process.
SummarySweet potato virus disease (SPVD) causes strap-shaped leaves, vein-clearing, puckering, chlorosis and stunting in susceptible sweet potato varieties and yields are much reduced. To investigate the tolerance of genotypes and obtain a better appraisal of yield loss caused by SPVD, eight sweet potato varieties showing symptoms of SPVD were studied for two years in an area where SPVD is severe. Two varieties, although showing symptoms, were tolerant of the disease; their yields were not significantly depressed by SPVD. Among the remaining six varieties, storage root fresh yields were reduced by 56–90% in plants showing SPVD symptoms. Marketable yields, as well as total and marketable numbers of storage roots were similarly depressed by SPVD in the less tolerant varieties. Significant correlations were found between disease severity rating and yield reduction among cultivars.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.