Abiotic stresses negatively affect crop development and yield. However, the use of seaweed extracts can alleviate production losses through improvement of the antioxidant system and synthesis of compatible osmolytes. The aim of this study was to assess the effects of Ascophyllum nodosum extract on antioxidant response and yield of common bean plants (Phaseolus vulgaris) under drought stress. Therefore, two methods of application (foliar spray and soil irrigation) and two doses (5 and 10 mL L-1) were tested, whereas untreated plants were used as control. There were no significant differences in malondialdehyde and hydrogen peroxide contents among treatments, indicating that application of seaweed extract did not change the oxidative status in treated plants when compared to the control ones. On the other hand, the use of seaweed extract increased proline content even prior to drought stress (46.3 to 145.4% when compared to the control), and this increment remained until the 10th day of stress (from 60.1 to 201.7% over the reference plants), supporting early evidences that A. nodosum extract is a plant elicitor. The yield parameters were not affected by the extract, probably due to the severe drought stress which plants were submitted. The results suggest that A. nodosum extract affects proline metabolism in Phaseolus vulgaris plants, making the synthesis of this osmolyte more responsive to drought stress because seaweed-treated plants presented a higher proline content than the control ones during the exposure to water deficit.

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaena were, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.

The use of plant growth regulators is directly related to the success of in vitro propagation, which is an advantageous alternative to obtain seedlings on a commercial scale. This study aimed to evaluate the in vitro development of ‘IAC 95-5000’ sugarcane seedlings after the addition of different doses of ethephon (0, 25, 50, 100 and 200 mg L-1) or gibberellic acid (0, 2.5, 5.0, 7.5 and 10.0 mg L-1) to the culture medium. Ethephon increased the number of tillers (up to 231.70%), reduced height of the main tiller (44.66 to 60.47%), and did not affect the shoot´s fresh and dry mass. On the other hand, gibberellin decreased the number of tillers and negatively changed biomass partitioning. It is concluded that the use of ethephon is a potential strategy to enhance in vitro production of ‘IAC 95-5000’ sugarcane seedlings, since it increased the number of usable shoots in subsequent subcultures, and its effects on height reduction can be reversible. However, the use of the tested doses of gibberellic acid is not recommended, because it impaired seedling development of this sugarcane variety.

Not all plant traits from all regions have been standardized or databased. Some ecosystems, such as tropical grasslands, are under-represented in such databases owing to the difficulty in assessing bud banks and evaluating clonal growth. This study aimed to (i) determine whether Brazilian morphological traits of belowground organs can be translated into categories used in the CLO-PLA database and (ii) assess the applicability of clonal and bud bank traits standardized in the CLO-PLA database for Brazilian Aldama species, which have specialized belowground organs and are able to resprout. In all, 165 species, including herbs, subshrubs and shrubs, of 37 genera from different Brazilian ecosystems, were evaluated. Not all the traditional Brazilian morphological categories could be translated into CLO-PLA traits, resulting in a lower number of categories and loss of information regarding plant morphology. Furthermore, clonal and bud bank traits could be only partially evaluated for Aldama, since some traits showed seasonal variation. The CLO-PLA classification focused on the organs in relation to the soil surface, the connection between mother and daughter shoots, and the origin of buds from which daughter shoots sprout. In the Brazilian classification, by contrast, anatomical features or early ontogeny of the organ are very important. Nevertheless, our results might form the basis for future comparative studies across ecosystems and biomes, for which common trait standardization is necessary. However, further research is needed to assess the functional morphology of clonal and bud bank traits in tropical regions.