Pachystegia rufa and allied rock daisies : rarity and threats
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Eagle's trees and shrubs of New Zealand.
The paintings are certainly beautiful and accurate depictions of the species. In only a few cases e.g., karaka, Coprosmn lucLda, hard beech, and Pseudowintera axillavis are the leaves not good likenesses of typical specimens. Flowers and fruits, as well as leaves, are shown, and the use of enlarged paintings to show details of floral structure, placentation and fruits will be helpful in identifications. Importantly, a uniform style and tone has been maintained throughout. In comparison with Mark and Adams' N e w Zealand Alpine Plants, the paintings by Audrey Eagle are if anything clearer and include more close-ups of flowers and fruits.
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.