Plant functional and taxonomic diversity in European grasslands along climatic gradients

Aim: European grassland communities are highly diverse, but patterns and drivers of their continental-scale diversity remain elusive. This study analyses taxonomic and functional richness in European grasslands along continental-scale temperature and precipitation gradients. Location: Europe. Methods: We quantified functional and taxonomic richness of 55,748 vegetation plots. Six plant traits, related to resource acquisition and conservation, were analysed to describe plant community functional composition. Using a null-model approach we derived functional richness effect sizes that indicate higher or lower diversity than expected given the taxonomic richness. We assessed the variation in absolute functional and taxonomic richness and in functional richness effect sizes along gradients of minimum temperature, temperature range, annual precipitation, and precipitation seasonality using a multiple general additive modelling approach. Results: Functional and taxonomic richness was high at intermediate minimum temperatures and wide temperature ranges. Functional and taxonomic richness was low in correspondence with low minimum temperatures or narrow temperature ranges. Functional richness increased and taxonomic richness decreased at higher minimum temperatures and wide annual temperature ranges. Both functional and taxonomic richness decreased with increasing precipitation seasonality and showed a small increase at intermediate annual precipitation. Overall, effect sizes of functional richness were small. However, effect sizes indicated trait divergence at extremely low minimum temperatures and at low annual precipitation with extreme precipitation seasonality. Conclusions: Functional and taxonomic richness of European grassland communities vary considerably over temperature and precipitation gradients. Overall, they follow similar patterns over the climate gradients, except at high minimum temperatures and wide temperature ranges, where functional richness increases and taxonomic richness decreases. This contrasting pattern may trigger new ideas for studies that target specific hypotheses focused on community assembly processes. And though effect sizes were small, they indicate that it may be important to consider climate seasonality in plant diversity studies

Alterações morfológicas foliares em abacaxizeiros cv. IAC "Gomo-de-mel" micropropagados e aclimatizados em diferentes condições de luminosidade Morphological alterations in leave of micropropagated pineapple plants cv. IAC "Gomo-de-mel" acclimatizated in different conditions of luminosity

Plantas micropropagadas geralmente apresentam dificuldades de adaptação ao meio ex vitro, sendo muitas vezes submetidas a processos de rustificação para minimizar os impactos decorrentes da mudança de ambiente. Uma vez que a folha e seus anexos destacam-se como importantes indicativos das estratégias adaptativas das plantas a ambientes adversos, este trabalho teve por objetivo comparar a anatomia foliar de plantas de abacaxi cv. IAC "Gomo-de-mel" cultivadas in vitro com microplantas aclimatizadas em diferentes condições de luminosidade, sob telado com 50% de sombreamento e em pleno sol para verificar a necessidade do processo de rustificação para este cultivar. Avaliações por meio de microscopia de luz e eletrônica de varredura da epiderme foliar, demonstraram aumento na densidade de escamas em ambas as superfícies das folhas, em microplantas dos ambientes ex vitro, principalmente em relação às que foram expostas diretamente ao sol. Observou-se ainda, aumento no espessamento da cutícula, na sinuosidade das células epidérmicas, e na distribuição e quantidade de fibras no mesofilo evidenciando a interferência das condições de luminosidade nas características morfológicas das microplantas. Essas alterações não prejudicaram o desenvolvimento das microplantas, indicando que não são necessárias etapas de rustificação para a aclimatização deste cultivar.<br>Microprapagated plants usually show difficulties to adapt to ex vitro conditions, and many times are submitted to the rustication process to aim the reduction of all the impacts resulting from the environmental changes. Once the leaf and its annexes are important indicators of adaptability strategies of the plants to adverse environmental conditions, the objective of this work was to compare the leaf anatomy of pineapple cv. IAC "Gomo-de-mel" in vitro cultivated plants with microplants acclimatized in different conditions of luminosity, under mesh, with 50 % of shading and directly exposed to sunlight, to verify the needed of rustication process on this cultivar. Evaluations of the leaf epidermis using light and electronic scanning microscopy showed an increase on scale density in both leaves surfaces of the ex vitro microplants, mainly related to the ones directly exposed to sunlight. Subsequent observations showed an increase on cuticle thickness, on wavy contours of epidermal cells, and on the distribution and quantity of mesophyll fibers, evidencing the light conditions interference in morphological characteristics of these microplants. These alterations had not harmed microplant development, showing that are not need of rustication stages on the acclimatization process of this cultivar

Upregulation of bundle sheath electron transport capacity under limiting light in C-4 Setaria viridis

C-4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO2 concentration at the site of CO2 fixation. C-4 plants benefit from high irradiance but their efficiency decreases under shade, causing a loss of productivity in crop canopies. We investigated shade acclimation responses of Setaria viridis, a model monocot of NADP-dependent malic enzyme subtype, focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO2 assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio were enhanced in LL BS cells, indicating a higher capacity for linear electron flow. Abundances of PSI, ATP synthase, Cytochrome b(6)f and the chloroplast NAD(P)H dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were also increased in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts were associated with a more oxidised plastoquinone pool in LL plants and the formation of PSII - light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results suggest that the supramolecular composition of PSII in BS cells is adjusted according to the redox state of the plastoquinone pool. This discovery contributes to the understanding of the acclimation of PSII activity in C-4 plants and will support the development of strategies for crop improvement, including the engineering of C-4 photosynthesis into C-3 plants