Abstract. A total of 24 samples from Sabellaria alveolata reefs have been collected and subjected to cluster analysis using the trophic dominance of each feeding guild as grouping variables. The result is the arrangement of samples by colony physical structure and S. alveolata dominance. Relating cluster groups to reef development phases reveals an inverse relationship between reef growth and the organization of the associated polychaete taxocoenosis. During the growth phase of the reef, S. alveolata dominates the community, excluding other taxa from colonization. Growth is followed by the destruction phase. Negative physical and biological factors for reef enlargement may open patches on the reef surface, allowing recruitment of other species and colony erosion. The end of this phase is represented by eroded reefs with high structural complexity and high species richness. Summary Sabellaria alveolata reefs reported from 13 localities in the study area have been classified according to their structural features into two main types: a) developed reefs, with considerable volume and a shape independent of the underlying substrate and b) eroded reefs, which form tiny encrusting plates covering the substrate. Based on cluster analysis each one of these may be subdivided according to SAQD values.

This review deals with two essential plant mineral nutrients, iron (Fe) and phosphorus (P); the acquisition of both has important environmental and economic implications. Both elements are abundant in soils but are scarcely available to plants. To prevent deficiency, dicot plants develop physiological and morphological responses in their roots to specifically acquire Fe or P. Hormones and signalling substances, like ethylene, auxin and nitric oxide (NO), are involved in the activation of nutrient-deficiency responses. The existence of common inducers suggests that they must act in conjunction with nutrient-specific signals in order to develop nutrient-specific deficiency responses. There is evidence suggesting that P-or Fe-related phloem signals could interact with ethylene and NO to confer specificity to the responses to Fe-or P-deficiency, avoiding their induction when ethylene and NO increase due to other nutrient deficiency or stress. The mechanisms responsible for such interaction are not clearly determined, and thus, the regulatory networks that allow or prevent cross talk between P and Fe deficiency responses remain obscure. Here, fragmented information is drawn together to provide a clearer overview of the mechanisms and molecular players involved in the regulation of the responses to Fe or P deficiency and their interactions.

Iron (Fe) and phosphorus (P) are two essential mineral nutrients whose acquisition by plants presents important environmental and economic implications. Both elements are abundant in most soils but scarcely available to plants. To prevent Fe or P deficiency dicot plants initiate morphological and physiological responses in their roots aimed to specifically acquire these elements. The existence of common signals in Fe and P deficiency pathways suggests the signaling factors must act in conjunction with distinct nutrient-specific signals in order to confer tolerance to each deficiency. Previous works have shown the existence of cross talk between responses to Fe and P deficiency, but details of the associated signaling pathways remain unclear. Herein, the impact of foliar application of either P or Fe on P and Fe responses was studied in P- or Fe-deficient plants of Arabidopsis thaliana, including mutants exhibiting altered Fe or P homeostasis. Ferric reductase and acid phosphatase activities in roots were determined as well as the expression of genes related to P and Fe acquisition. The results obtained showed that Fe deficiency induces the expression of P acquisition genes and phosphatase activity, whereas P deficiency induces the expression of Fe acquisition genes and ferric reductase activity, although only transitorily. Importantly, these responses were reversed upon foliar application of either Fe or P on nutrient-starved plants. Taken together, the results reveal interactions between P- and Fe-related phloem signals originating in the shoots that likely interact with hormones in the roots to initiate adaptive mechanisms to tolerate deficiency of each nutrient.

Cleistogamous capitula formed by Centaurea melitensis display a number of morphological and functional changes with respect to chasmogamous capitula that ensure self-fertilization. Because no studies have hitherto addressed the evolution of cleistogamy in Asteraceae, it was considered useful to ascertain whether these changes are attributable to one or more of the heterochronic processes reported in the literature. Bivariate allometric analyses were performed, and changes were represented graphically using Gould's clock models for size, shape, and age of several capitulum and floret structures. Results suggest that the partially paedomorphic appearance of cleistogamous with respect to chasmogamous capitula is attributable to three processes: (1) early onset of floral development (predisplacement), (2) decreased growth rate of the whorls studied (except gynoecium width) and (3) early offset time (progenesis). The latter appears to play the most significant role in the origin of the cleistogamous capitulum.

Aim of study: Crop phenology is a critical component in the identification of impacts of climate change. Then, the assessment of germplasm collections provides relevant information for cultivar selection and breeding related to phenology, being the base for identifying adaptation strategies to climate change.Area of study: The World Olive Germplasm Bank located at IFAPA Centre “Alameda del Obispo” (WOGB-IFAPA) in Cordoba (Southern Spain) was considered for the study.Material and methods: Data gathered for nine years on flowering and ripening time of olive cultivars from WOGB-IFAPA were evaluated. Thus, full flowering date (FFD) for 148 cultivars and ripening date (RD) for 86 cultivars, coming from 14 olive growing countries, were considered for characterization of olive phenology and for calibration/validation of phenological models.Main results: The characterization of WOGB-IFAPA has allowed the identification of cultivars with extreme early (‘Borriolenca’) and late (‘Ulliri i Kuq’) flowering as well as the ones with extreme early (‘Mavreya’) and late (‘Gerboui’) ripening dates. However, the very limited inter-cultivar variability, especially for FFD, resulted in a non-optimal simulation models performance. Thus, for FFD and RD the root mean square error was around 6 and 24 days, respectively. The limited inter-cultivar variability was associated to the low average temperatures registered during winter at WOGB-IFAPA generating an early accumulation of the chilling requirements, thus homogenizing FFD of all the analyzed cultivars.Research highlights: The identification of cultivars with early FFD and late RD provides useful information for breeding programs and climate change studies for identifying adaptation strategies.