ABSTRACT
To prolong their vase life, cut flowers are commonly kept in holding solutions. These must include a biocide to retard bacterial growth. In this study, the effect of nanosilver (NS) on certain aspects of senescence in cut garden cosmos (Cosmos bipinnatus) flowers was compared to that of the commonly used 8-hydroxyquinoline citrate (8-HQC). In combination with sucrose, both biocides prolonged cosmos vase life but did not prevent the occurrence of stem blockages. NS was more effective in limiting a reduction in endogenous soluble carbohydrates. The malondialdehyde (MDA) contents increased in senescing ray florets, both in intact and control cut flowers held in water. Both biocides were comparably effective in limiting this effect. The hydrogen peroxide content tripled in intact flowers but dropped in flowers held in water or the 8-HQC solutions; in flowers kept in NS solutions its increase was moderate. Also, the catalase activity increased in intact flowers but dropped in all cut flowers. Both biocides had similar effects on the enzyme activity, in both pure solutions and with sucrose. Most of these parameters were not significantly correlated with vase life. Overall, the effect of nanosilver on senescence in cut cosmos flowers was similar to that of 8-HQC.
ABSTRACT
During the vase life of cut stems obstruction of xylem vessels occurs due to microbial growth, formation of tyloses, deposition of materials in the lumen of xylem vessels and the presence of air emboli in the vascular system. Such obstructions may restrict water uptake and its transport towards upwards thus lowering their ornamental value and longevity of cut flowers. Clematis is a very attractive plant material which may be used as cut flower in floral compositions. Nothing is known about the histochemical or cytological nature of xylem blockages occurring in cut stems of this plant. This study shows that in clematis, tyloses are the main source of occlusions, although bacteria and some amorphic substances may also appear inside the vessels. A preservative composed of 200 mg dm(-3) 8-HQC (8-hydroxyquinolin citrate) and 2% sucrose arrested bacterial development and the growth of tyloses. This information can be helpful in the development of new treatments to improve keeping qualities of cut clematis stems.
Subject(s)
Clematis/metabolism , Plant Stems/metabolism , Xylem/metabolism , Microscopy, ElectronABSTRACT
Doubled haploids are an established tool in plant breeding and research. Of several methods for their production, androgenesis is technically simple and can efficiently produce substantial numbers of lines. It is well suited to such crops as hexaploid triticale. Owing to meiotic irregularities of triticale hybrids, aneuploidy may affect the efficiency of androgenesis more severely than in meiotically stable crops. This study addresses the issue of aneuploidy among androgenic regenerants of triticale. Plant morphology, seed set and seed quality were better predictors of aneuploidy, as determined cytologically, than flow cytometry. Most aneuploids were hypoploids and these included nullisomics, telosomics, and translocation lines; among 42 chromosome plants were nulli-tetrasomics. Rye chromosomes involved in aneuploidy greatly outnumbered wheat chromosomes; in C(0) rye chromosomes 2R and 5R were most frequently involved. While the frequency of nullisomy 2R was fairly constant in most cross combinations, nullisomy 5R was more frequent in the most recalcitrant combination, and its frequency increased with time spent in culture with up to 70% of green plants recovered late being nullisomic 5R. Given that 5R was not involved in meiotic aberrations with an above-average frequency, it is possible that its absence promotes androgenesis or green plant regeneration. Overall, aneuploidy among tested combinations reduced the average efficiency of double haploid production by 35% and by 69% in one recalcitrant combination, seriously reducing the yield of useful lines.
