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Spatial and temporal variation in functional traits allows trees to adjust to shifting environmental conditions such as water stress. However, the change of traits, both mean and variances, along water availability gradients and across growing seasons, as well as their covariation with tree performance, have been rarely assessed. We examined intraspecific trait variation in coexisting evergreen (Quercus ilex ssp. ilex and Q. ilex ssp. ballota) and deciduous (Quercus faginea and Quercus humilis) Mediterranean oaks along a wide water availability gradient in northeastern Spain during six years. We measured leaf area (LA), shoot twig mass (Sm), leaf mass per area (LMA) and the ratio of shoot twig to leaf biomass (Sm:Lm). We characterized tree performance through basal area increment (BAI) and drought resilience indices. Higher variation was found within individuals than between individuals across populations and years. Within species, we found trait adjustments toward more conservative water-use (low LA and Sm and high LMA) with increasing drier conditions. Intraspecific trait variation was constrained by water availability, particularly on the deciduous species. In Q. ilex, trait variance of LMA positively covaried with annual BAI, whereas variance of LA, Sm and Sm:Lm was positively related to resistance and resilience against the severe 2012 drought in deciduous oaks. Our results support a tradeoff between the ability to tolerate drought and the capacity to cope with unpredictable changes in the environment through increased intraspecific trait variation, which may have implications on tree performance in the face of increased extreme events.

Plants have to cope with different biotic and abiotic stresses, such as the attacks of pathogens and herbivores, high irradiance, droughts, salt stress or nutrient deficiencies throughout their lifetime. These environmental perturbations lead to the regulation of the “primary” and “secondary” carotenoid network. The formers are produced and stored in plastids and they are necessary for photosynthesis and related functions. Otherwise, secondary carotenoids are derivatives of primary carotenoids. They perform other important functions not related to the photosynthetic process but essential for plant survival as regulators of growth and development or as signal molecules at all levels of plant organization. This review provides a complete revision of the status of all these carotenoids, highlighting their newly discovered functions involved in plant-environment interaction. Concurrently, this review covers recent information on how carotenoids perform critical functions for the survival of animals (including humans) and the way they are suitable diagnostic tools for assessing the functioning of terrestrial ecosystems.

In the current scenario of climate change, plants need to overcome a great amplitude of temperatures and increasingly common droughts in the very same space. Gesneriads are a worldwide family of plants in which many “resurrection” species have arisen: plants with the ability to withstand long periods of time with very little water content and successfully revive upon water availability. Due to their rocky and mountainous habitat, many of them have to face a great temperature variability and freezing temperatures, and indeed, their resurrection ability and freezing tolerance share similar metabolic responses. Tolerance of gesneriads to different environmental stresses is thought to be applicable in crop growth improvement, but their difficult indoor cultivation and outdoor accessibility are major obstacles for their study. Therefore, this review aims to identify common patterns in the already known resurrection species to propose new tentative resurrection gesneriads, as well as gather the metabolic responses to desiccation and freezing stress as a way of making them more reachable to the scientific community.

[EN] Main conclusion Plastoglobules are ubiquitous under non-stress conditions and their morphology, closely related to their composition, changes differently depending on the specific stress that the plant undergoes. Plastoglobules are lipoprotein structures attached to thylakoid membranes, which participate in chloroplast metabolism and stress responses. Their structure contains a coating lipid monolayer and a hydrophobic core that differ in composition. Their function in chloroplasts has been studied focussing on their composition. However, we currently lack a comprehensive study that quantitatively evaluates the occurrence and morphology of plastoglobules. Following a literature search strategy, we quantified the main morphological attributes of plastoglobules from photosynthetic chloroplasts of more than 1000 TEM images published over the last 53 years, covering more than 100 taxa and 15 stress types. The analysis shows that plastoglobules under non-stress conditions are spherical, with an average diameter of 100-200 nm and cover less than 3% of the chloroplast cross-section area. This percentage rises under almost every type of stress, particularly in senescence. Interestingly, an apparent trade-off between increasing either the number or the diameter of plastoglobules governs this response. Our results show that plastoglobules are ubiquitous in chloroplasts of higher plants under non-stress conditions. Besides, provided the specific molecular composition of the core and coat of plastoglobules, we conclude that specific stress-related variation in plastoglobules attributes may allow inferring precise responses of the chloroplast metabolism.

Evergreen plants growing at high latitudes or high elevations may experience freezing events in their photosynthetic tissues. Freezing events can have physical and physiological effects on the leaves which alter leaf optical properties affecting remote and proximal sensing parameters. We froze leaves of six alpine plant species (Soldanella alpina, Ranunculus kuepferi, Luzula nutans, Gentiana acaulis, Geum montanum, and Centaurea uniflora) and three evergreen forest understorey species (Hepatica nobilis, Fragaria vesca and Oxalis acetosella), and assessed their spectral transmittance and optically measured pigments, as well as photochemical efficiency of photosystem II (PSII) as an indicator of freezing damage. Upon freezing, leaves of all the species transmitted more photosynthetically active radiation (PAR) and some species had increased ultraviolet-A (UV-A) transmittance. These differences were less pronounced in alpine than in understorey species, which may be related to higher chlorophyll degradation, visible as reduced leaf chlorophyll content upon freezing in the latter species. Among these understorey forbs, the thin leaves of O. acetosella displayed the largest reduction in chlorophyll (-79%). This study provides insights into how freezing changes the leaf optical properties of wild plants which could be used to set a baseline for upscaling optical reflectance data from remote sensing. Changes in leaf transmittance may also serve to indicate photosynthetic sufficiency and physiological tolerance of freezing events, but experimental research is required to establish this functional association.

Los manglares son ecosistemas únicos que crecen en aguas salobres en las fronteras de los litorales tropicales; representan un enorme valor científico, ecológico, económico y cultural. En Nicaragua representan una gran fuente de recursos económicos para las poblaciones locales. Las especies más afectadas por la tala son Rizophora mangle L, Rhizophora harrisonii y Rizhophora racemosa G. Mey. Debido a que estas especies presentan características fenotípicas similares su separación como especie es difícil. Por lo que el objetivo de este trabajo fue diferenciar morfofisiológicamente las tres especies del género Rhizophora. Para llevar a cabo este estudio se utilizaron muestras foliares de las especies R. mangle, R. harrisonii Leechm y R. racemosa provenientes de la Isla Juan Venado. Se realizaron comparaciones morfológicas y análisis de pigmentos y tocoferoles. La actividad de los sistemas fotoprotectores, resultaron ser muy variables intraespecíficamente. El contenido total de tocoferoles fue muy diferente entre las tres especies siendo R. racemosa la de máxima concentración y R.harrisonii la de menor. El papel del y-tocoferol en la tolerancia a la salinidad podría ser responsable de las diferencias interespecíficas. La distinta composición en tocoferoles podría ser utilizada como parámetro bioquímico de distinción interespecífica.

Resurrection plants are able to deal with complete dehydration of their leaves and then recover normal metabolic activity after rehydration. Only a few resurrection species are exposed to freezing temperatures in their natural environments, making them interesting models to study the key metabolic adjustments of freezing tolerances. Here, we investigate the effect of cold and freezing temperatures on physiological and biochemical changes in the leaves of Haberlea rhodopensis under natural and controlled environmental conditions. Our data shows that leaf water content affects its thermodynamical properties during vitrification under low temperatures. The changes in membrane lipid composition, accumulation of sugars, and synthesis of stress-induced proteins were significantly activated during the adaptation of H. rhodopensis to both cold and freezing temperatures. In particular, the freezing tolerance of H. rhodopensis relies on a sucrose/hexoses ratio in favor of hexoses during cold acclimation, while there is a shift in favor of sucrose upon exposure to freezing temperatures, especially evident when leaf desiccation is relevant. This pattern was paralleled by an elevated ratio of unsaturated/saturated fatty acids and significant quantitative and compositional changes in stress-induced proteins, namely dehydrins and early light-induced proteins (ELIPs). Taken together, our data indicate that common responses of H. rhodopensis plants to low temperature and desiccation involve the accumulation of sugars and upregulation of dehydrins/ELIP protein expression. Further studies on the molecular mechanisms underlying freezing tolerance (genes and genetic regulatory mechanisms) may help breeders to improve the resistance of crop plants.

The summer climate in Maritime Antarctica is characterised by high humidity and cloudiness with slightly above zero temperatures. Under such conditions, photosynthetic activity is temperature-limited and plant communities are formed by a few species. These conditions could prevent the operation of the photoprotective xanthophyll (VAZ) cycle as low irradiance reduces the excess of energy and low temperatures limit enzyme activity. The VAZ cycle regulates the dissipation of the excess of absorbed light as heat, which is the main mechanism of photoprotection in plants. To test whether this mechanism operates dynamically in Antarctic plant communities, we characterised pigment dynamics under natural field conditions in two representative species: the moss Polytrichum juniperinum and the grass Deschampsia antarctica. Pigment analyses revealed that the total VAZ pool was in the upper range of the values reported for most plant species, suggesting that they are exposed to a high degree of environmental stress. Despite cloudiness, there was a strong conversion of violaxanthin (V) to zeaxanthin (Z) during daytime. Conversely, the dark-induced enzymatic epoxidation back to V was not limited by nocturnal temperatures. In contrast with plants from other cold ecosystems, we did not find any evidence of overnight retention of Z or sustained reductions in photochemical efficiency. These results are of interest for modelling, remote sensing and upscaling of the responses of Antarctic vegetation to environmental challenges.

Wood formation during the growing season is shaped by the intra-annual variability of climatic conditions. In the Mediterranean, the cambial activity is seasonally constrained by winter low temperature and summer drought, resulting in bimodal growth patterns. Although bimodal growth is an ecologically important adaptation of woody species to seasonally dry environments, its variability across space and among species remains unclear. We combined direct monitoring of intra-annual radial growth using dendrometers and xylogenesis micro-sampling with indirect wood formation modeling to assess growth bimodality for two coexisting oak species across six sites in North-Eastern Spain. We focused on species with two contrasting life strategies, evergreen with diffuse-porous wood (Quercus ilex) and winter deciduous with ring-porous wood (Q. faginea/Q. pubescens). Study sites spanned from oceanic areas with high autumn precipitation to dry continental inland regions. We hypothesized that growth bimodality reflects the interaction between local precipitation patterns and species-specific traits. Our results revealed cambial activity in autumn after summer quiescence across the entire region and for both oak species. However, growth bimodality and the relative contribution of the autumn growth peak to the total annual growth was geographically structured and species-specific. Growth was unimodal under continental and Atlantic conditions. By contrast, growth bimodality was significant along the Mediterranean coast, where precipitation showed a bimodal pattern. Moreover, evergreen Q. ilex showed more growth bimodality compared with deciduous Q. faginea/Q. pubescens at Mediterranean sites. Different intra-annual distribution of radial growth could facilitate coexistence of both oak species through temporal niche partitioning. The growth bimodality helps to compensate for reduced growth in summer by autumn cambial resumption and, therefore, the differences in its intensity between si