NITRATE REDUCTASE ACTIVITY ( NRA ) AT VEGETATIVE AND REPRODUCTIVE CONDI [ TIONS IN SACCHA RUM CULTIVAR CO
Regulations of flowering and induction of flowering in nonflowering clones of Saccharum has been found possible by the application of extra light (EL) and extra dark (ED) treatments. As to the effect of EL, ED and 'switch over' treatment from EL to ED on NRA relation to flowering NRA was found to be low at vegetative stage and as the plants reached the symptom stage. The activity reached a maximum value and thereafter showing a deckle with progress in flower development. Examination of gemplasm collection for NRA in clones of Saccharum species known to differ in their flowering behaviour was suggested.
Contributions to a biochemical study of sugarcane
SummaryFrom a study of the total iron (FeT), acid-soluble iron (FeS) and chlorophyll in the leaves of cane varieties, the fraction of iron bearing relation to chlorophyll (active iron, FeA) and that not related to chlorophyll (residual iron, FeR) have been calculated. FeR appears to bear relation to the growth of the cane varieties. A study of the variation of FeR/FeA ratio seems to be of help in determining whether the tendency of the plant, at a particular time, is more towards growth or accumulation of sucrose. It is shown that the factorf=FeR × FeS/FeA2 can serve as an index in the characterisation of cane varieties, in relation to early or late ripening character, even at an young age of 5 months.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.