Leaf Renewal Research Articles

PHENOLOGY OF Trichocline catharinensis Cabrera IN AN AREA OF ALTITUDE FIELDS, URUPEMA, SANTA CATARINA, BRAZIL

The high-altitude fields in Santa Catarina are endowed with a great richness of species with economic potential, such as Trichocline catharinensis Cabrera (Asteraceae), popularly known as "cravo-do-campo" (field carnation), a herbaceous species that occurs naturally in southern Brazil. In order to indicate its ornamental potential, the study aimed to monitor the phenology of the species in a native field area, in the Alto-Montane Mixed Ombrophilous Forest, with altitudes ranging from 1450 to 1750 meters, located within the Private Natural Heritage Reserve (RPPNE) Complexo Serra da Farofa, at Fazenda das Nascentes, Urupema, SC. For 13 months (from April 2015 to April 2016), 15 specimens of T. catharinensis were monitored biweekly. Vegetative and reproductive phenophases were recorded regarding activity index, presence (1) and absence (0) of phenophases, and their synchrony was subsequently estimated. The species is evergreen with annual leaf renewal; once in every month evaluated, the species showed budding and leaf senescence. All specimens had flowering and fruiting records, with flowering starting in January, with a peak of floral buds and anthesis in February and March, respectively, and fruiting from March to July, with synchronous flowering. Correlations were recorded only for the phenophases of budding and floral buds with maximum and minimum temperatures. The wide flowering period may be a positive factor for its ornamental potential, as it presents dark green foliage and showy yellow capitula.

Effect of simulated extreme rainfall on the vegetative phenology of perennial and annual herbaceous plants from a Brazilian dry forest.

Detecting changes in the phenological responses of herbaceous species as a function of predicted climate change is important for forecasting future scenarios for the functioning of dry tropical forests, especially when predicting an increase in the frequency and intensity of extreme droughts. Because of the sensitivity of plants to water availability, our study hypothesizes that if years become drier or wetter, herbaceous plants will synchronously change the onset, duration, and intensity of their vegetative phenophases. We used a historical series of 60 years of precipitation observations for the Caatinga vegetation to define daily average of precipitation for rainy (Twet), median (Tcontrol), and dry (Tdry) years. We simulated past average daily rainfall (Twet, Tcontrol, and Tdry) while growing two herbaceous perennials and two herbaceous annuals. We monitored plant growth and measured the activity (absence or presence) and intensity of vegetative phenophases. We used circular statistical analysis to assess differences between treatments. Our results revealed that leaf production was seasonal but relatively uniform for perennial species and highly seasonal (wet season) for annual species. Simulated dry years induced lower leaf emergence concentrated over a few months in annual species, but this effect was more strongly significant in one of the two perennial species. Both annual and perennial species can experience delayed and less intense leaf abscission during the rainy season in years with below-average precipitation. In contrast, large voluminous rains in years with above-average precipitation can accelerate and intensify the process of leaf renewal. If future precipitation reductions occur, the changes in phenological response indicate that the cover of annual and perennial herbaceous species in this study will likely decrease, altering the landscape and functioning of dry tropical forests. However, the potential trade-offs observed may help populations of these species to persist during years of severe drought in the Caatinga.

Climatic triggers of the phenophases of Elaphoglossum macrophyllum in Southern Brazil

Abstract Although ferns have a prominent floristic position with their richness center in Atlantic Forest in Brazil, the effect of climate on their phenophases is still poorly known. This group shows different phenological patterns due to the great latitudinal extent, the strong climatic seasonality of this forest, and the leaf dimorphism found in some species. In this scenario, we evaluated the phenological events of Elaphoglossum macrophyllum and related them to climatic factors. Fertility, leaf renewal, and leaf senescence in E. macrophyllum were analyzed based on the monthly survey of 152 plants growing for two years in the subtropical Atlantic Forest, Brazil. The three analyzed phenophases showed the same intra-annual pattern regarding continuity, regularity, and seasonality along the two years, revealing a phenological pattern for the specie. The generalized additive models for location, scale, and shape (GAMLSS) indicated that photoperiod was the most important trigger for fertility and leaf renewal. Temperature, as an important phenology modulator, was related to leaf renewal and senescence. Our data indicate that E. macrophyllum, an endangered species in southern Brazil, withstands the consequences of seasonal climatic variations without the individual mortality, total leaf shedding, or fertility loss.

Phenology of Araucaria Forest fern communities: comparison of the influence of natural edge, artificial edge, and forest interior.

The edge effect, triggered by habitat fragmentation, alters forest microclimates and influences the life cycle of plants. Phenology may indicate the first changes in phenological patterns in response to the effects of climate change. Climate regulates the phenology of ferns and climatic triggers influence plants in tropical and subtropical regions differently. This study analyzed and compared the phenology of fern communities of three sub-areas - natural edge, artificial edge, and forest interior - of a fragment of Araucaria Forest in the Floresta Nacional de São Francisco de Paula, Rio Grande do Sul, Brazil, and its relationship with meteorological, astronomical, and edaphic variables. Abiotic and edaphic data were monitored concomitantly with phenological data (leaf renewal and senescence and sporangia formation) in each sub-area over a biennium. Temperature, air humidity, and soil moisture, which undergo changes with the edge effect, influenced edge plants. Leaf renewal was the main phenophase showing strong indication of changes in vegetative patterns in natural and artificial edge communities. Among the communities, that of the artificial edge signaled phenological changes that could compromise the development of ferns if effects intensify over time. In this respect, the phenology of artificial edge ferns differed from that of plants growing in originally natural formations (natural edge and forest interior), showing that exogenous transformations represent a new environmental situation for ferns to develop.

Morphological and phenological strategies for flooding tolerance in Cerrado and Pantanal trees: implications for restoration under new legislation

In 2012, the Native Vegetation Protection Law 12,651 decreased the extent of Areas of Permanent Preservation in Brazil. While previously the distance from water was measured during the rainy season, the new version only considered the extent of the regular watercourse. This change affects conservation and restoration sites, and restoration programs need to be modified based on the new legislation. For instance, more flood‐tolerant species need to be planted, given the higher probability that restoration efforts will be lost during flooding. To identify species suitable for the restoration of such areas, we tested if plants that develop morphological structures to tolerate waterlogging stress are more resistant to hypoxia caused by flooding and can recover better afterwards. We experimentally evaluated survival and morphological or phenological strategies (root dry mass, height, basal diameter, adventitious roots, lenticels, and leaf renewal) of 13 tree species from the Cerrado and Pantanal biomes of Brazil. After 56 days of simulated inundation and 56 days of post‐inundation recovery, we found that all study species were able to survive on waterlogged soil and to recover after the flood, and they can be used to restore periodically flooded riparian forests within the new legal zone. Our study is particularly relevant, as climate change is expected to increase flooding. As environmental laws change and new areas get restored including those in artificially flooded areas, such as on banks of hydroelectric dams, the experimental approach introduced in this study should be replicated with other species from various phytogeographic domains worldwide.

Study on the salinity tolerance in Citrus latifolia (Yu. Tanaka) Tanaka

Saltwater intrusion in the Mekong Delt, an urgent problem, affected the growth of fruit trees in general and Citrus latifolia (Yu. Tanaka) Tanaka in particular. Sodium chloride in saline soils cause the water stress on plant roots leading to the leaf senescence and death of plant. Therefore, in this study, the salinity tolerance of the studied plant was investigated under conditions of additional sodium chloride in soil at various concentrations (from 0 to 16 g/L) to determine the salinity tolerance threshold of the plants, and then the roots were water irrigated and the leaves were sprayed by KNO3 solution at concentrations from 0 to 10 g /L to improve the salinity tolerance. The results showed that after 2 weeks of treatment of sodium chloride 4‒16 g/L, the increased saline caused the osmotic stress, increased the defoliation but reduced the leaf renewal, the fresh weight, the chlorophyll index, the Citrus latifolia growth, and decreased the aperture size and the photosynthetic intensity over time. The salinity stress promoted the ligninization in the rhizosphere parenchyma cells, reduced the root renewal and elongation. In addition, treatments for the plant recovery were also carried out by irrigating at the roots and spraying KNO3 10 g/L solution on the leaves. After 3 and 6 weeks, irrigation treatments could only recover plants from sodium chloride at 4‒8 g/L, indicating by the new leaf formation, the maintenance of the chlorophyll content in leaves and the decrease of the proline content. Sodium chloride solutions of 12 and 16 g/L caused a complete death of plants which could not be recovered after 6 weeks of watering. The treatment of sodium chloride combining with KNO3 10 g/L spray helped the aperture opening and increasing the proline accumulation in leaves and roots. In addition, role of endogenous plant growth regulators was also discussed to clarify physiological changes in saline stress conditions.

Canopy dynamics in a tropical Atlantic forest mosaic in southeastern Brazil

The influence of seasonality on leaf production and canopy dynamics was evaluated in four areas in the Rio Doce State Park—RDSP, which is part of the Atlantic Forest Biosphere Reserve in Marlieria city, Minas Gerais State, southeastern Brazil. Leaf production was determined during a period of two years (2007 I and 2008 II) and on a monthly basis (25 collectors of 0.25 m2) to determine dry mass and specific leaf area at four different areas (Preta, Central, Garapa, and Anibal). Leaf area index of canopy values (LAI-canopy) was determined using hemispheric canopy photographs in October 2008 and March 2009. Specific leaf area of the leaf litter samples (LAI-SLA) was calculated during November (2008) and March (2009). Leaf production followed a seasonal rhythm, with higher cumulative production between the middle of the dry season and beginning of the rainy season (August to November). The LAI-canopy values did not have significant variations between the four areas evaluated; however, significant difference between seasons was observed in the Anibal and Central areas. The LAI-SLA was higher in Anibal while Preta, Central, and Garapa presented similar values. Our results evidenced the possible influence of the leaf fraction on canopy dynamics and LAI and revealed the rapid leaf renewal characteristics of seasonal semideciduous forests. We observed spatial heterogeneity of semideciduous forests maintaining a partial canopy cover even in the season with the greatest leaf fall. This explains to the absence of any significant correlation between leaf production and LAI-canopy as observed in the present study.

Spring Leafing Phenology Favors Younger Culms of Moso Bamboo: Aspects From Water Use Relations.

As the most widely distributed giant running bamboo species in China, Moso bamboo (Phyllostachys edulis) can accomplish both development of newly sprouted culms and leaf renewal of odd-year-old culms within a few months in spring. The two phenological events in spring may together change water distribution among culms in different age categories within a stand, which may differ from our conventional understanding of the negative age effect on bamboo water use. Therefore, to explore the effect of spring shooting and leaf phenology on age-specific water use of Moso bamboo and potential water redistribution, we monitored water use of four culm age categories (newly sprouted, 1-, 2-, and 3-year-old; namely A0, A1, A2, A3) in spring from March to June 2018. For newly sprouting culms, the spring phenological period was classified into five stages (incubation, culm-elongation, branch-development, leafing, established). Over these phenological stages, age-specific accumulated sap flux density showed different patterns. The oldest culms, A3, were not influenced by leaf renewal and kept nearly constant and less water use than the other aged culms. However, A2, which did not renew their leaves, had the most water use at the two initial stages (incubation, culm-elongation) but consumed less water than A0 and A1 after the fourth stage (leafing). At the end of June, water use of the four age categories sorted in order of A0 > A1 > A2 > A3, which confirms the conventional thought and observations, i.e., a negative age effect. The results indicate that new leaf flushing may benefit younger culms (A1 and A0) more than older culms (A2 and A3), i.e., increasing their transpiration response to radiation and share of the stand transpiration. With the underground connected rhizome system, the bamboo stand as an integration seems to balance its water use among culms of different ages to support the water use of freshly sprouted culms during their developing period.

Monitoring Mega-Crown Leaf Turnover from Space

Spatial and temporal patterns of tropical leaf renewal are poorly understood and poorly parameterized in modern Earth System Models due to lack of data. Remote sensing has great potential for sampling leaf phenology across tropical landscapes but until now has been impeded by lack of ground-truthing, cloudiness, poor spatial resolution, and the cryptic nature of incremental leaf turnover in many tropical plants. To our knowledge, satellite data have never been used to monitor individual crown leaf phenology in the tropics, an innovation that would be a major breakthrough for individual and species-level ecology and improve climate change predictions for the tropics. In this paper, we assessed whether satellite data can detect leaf turnover for individual trees using ground observations of a candidate tropical tree species, Moabi (Baillonella toxisperma), which has a mega-crown visible from space. We identified and delineated Moabi crowns at Lopé NP, Gabon from satellite imagery using ground coordinates and extracted high spatial and temporal resolution, optical, and synthetic-aperture radar (SAR) timeseries data for each tree. We normalized these data relative to the surrounding forest canopy and combined them with concurrent monthly crown observations of new, mature, and senescent leaves recorded from the ground. We analyzed the relationship between satellite and ground observations using generalized linear mixed models (GLMMs). Ground observations of leaf turnover were significantly correlated with optical indices derived from Sentinel-2 optical data (the normalized difference vegetation index and the green leaf index), but not with SAR data derived from Sentinel-1. We demonstrate, perhaps for the first time, how the leaf phenology of individual large-canopied tropical trees can directly influence the spectral signature of satellite pixels through time. Additionally, while the level of uncertainty in our model predictions is still very high, we believe this study shows that we are near the threshold for orbital monitoring of individual crowns within tropical forests, even in challenging locations, such as cloudy Gabon. Further technical advances in remote sensing instruments into the spatial and temporal scales relevant to organismal biological processes will unlock great potential to improve our understanding of the Earth system.

Unraveling the Complexity of Coffee Leaf Rust Behavior and Development in Different Coffea arabica Agroecosystems.

Crop health management systems can be designed according to practices that help to reduce crop losses by restricting pathogen development and promoting host plant growth. A good understanding of pathogen and host dynamics, which are interdependent, is therefore needed. In this article, we used a holistic approach to explain the behavior of coffee leaf rust (CLR), a major coffee disease. We monitored coffee plant and CLR dynamics simultaneously in plots under different disease management and agroforestry systems. Diseased leaves were also collected to characterize inoculum stock and rust life stages (latent rust area, area with uredospores, necrosis due to rust) through picture analysis. We used structural equation modeling to obtain an overview of CLR pathosystem functioning on a plant scale. This overview integrates processes such as disease dilution by host leaf renewal, direct and indirect effects of fruit load on CLR development, antagonistic effects of shading depending on rust life stages, the tonic effect of copper-based fungicides on leaf retention, and effects on rust life stages depending on fungicide types. From our results, we also deduced that the inoculum stock could be calculated in unsprayed plots from the rust area with uredospores, with uredospores at 58 × 103 cm-2, on average.

Genetic variation in nutrient uptake and nutrient use efficiency of oil palm

ABSTRACTObservations of the vegetative and reproductive biomass produced annually and the mineral element contents have been conducted on diverse oil palm plant materials tested in a genetic test in Indonesia. The results show that the nutrient uptake (for trunk growth, leaf renewal and bunch export) greatly varies (CV = 10% for N uptake and 17% for K uptake) with the origins of the planting materials considered. For equivalent production, the uptake in nutrients of certain plant material may differ very significantly; for the same level of uptake in nutrients, production can vary significantly. This study supports the hypothesis that the optimal nutrient thresholds are intrinsically linked to the plant material. It assumes that some planting materials have different needs and that a fertilizer regime could be adapted to their specific needs without losses in performance. To confirm these assumptions, the need of implementing specific experimental devices with differentiated fertilization regimes is discussed.

Aporte de hojarasca y renovación foliar del manglar en un sistema estuarino del Sureste de México

Los patrones de producción de hoj arasca fueron estudiados en Pom-Atasta, un sistema estuarino asociado á la Laguna de Términos Campeche, México. Se seleccionaron cuatro rodales de manglar, contrastantes por sus condiciones de influencia de marea. Se colocaron al azar diez trampas en cada sitio para la colecta de hojarasca, estas fueron revisadas a intervalos mensuales durante un ciclo anual (1995-96). El material recolectado fue clasificado, secado y pesado. La floración de Avicennia germinans se presentó desde junio hasta septiembre; Rhizapllara mangle presentó flores e hipocotilos

Ethnoecology of the palm Brahea dulcis (Kunth) Mart. in central Mexico.

BackgroundThere have been few studies on the sustainable use of non-timber forest products in arid and semi-arid zones. The palm Brahea dulcis has been one of the most important resources in semi-arid Mesoamerica, since pre-Hispanic times. Currently, some populations grow within protected natural areas, representing both a challenge and an opportunity for local development. This ethnoecological study of B. dulcis in central Mexico aimed to evaluate their uses, harvesting context, and potential for exploitation, in order to give practical advice on their best use and management.MethodsEthnographic and ecological information was obtained in Barranca de Metztitlán Biosphere Reserve and Valle del Mezquital, Mexico. We studied the population structure and density; additionally, we evaluated the rate of leaf production, leaf renewal rate, percent survival of new leaves, the development of reproductive structures and performed a one-year defoliation experiment (involving a control and four treatments including a mix of semiannual and annual frequency of harvest and removal of two new leaves and/or two mature leaves).ResultsTwenty uses of the palm were recorded in the study area. Religious/symbolic and handicraft uses are highlighted. The population density of this species was the highest reported for the genus (1244 ± 231.7 ind/ha). The leaf production rate was the highest reported for arborescent palms of the Americas (11.83 ± 0.036 leaves/individual/year). The sexual reproductive cycle was 2.3 years long. A one-year defoliation experiment did not show statistically significant differences. Recommendations include: 1) implement management focused on increasing the abundance and quality of this useful resource in Metztitlán; 2) employ a strategy of focusing on ethnicity and gender in promoting their exploitation; 3) learn from theoretical frameworks of other non timber forest product studies.ConclusionsWe propose that Brahea dulcis is the palm with the highest potential for sustainable use in the arid and semi-arid zones of Mexico. The challenge to improving management includes simplifying the legal protection framework, promoting uses and developing a market strategy. Collaborations to share experiences with peasant farmers from Guerrero is recommended. We further recommend the development of a governmental strategy to enhance and reassess this important resource.Electronic supplementary materialThe online version of this article (doi:10.1186/1746-4269-11-1) contains supplementary material, which is available to authorized users.

Fenologia e produção de frutos de Caryocar brasiliense Cambess. E Enterolobium gummiferum (Mart.) J.F.Macbr. em diferentes regimes de queima

O conhecimento dos períodos reprodutivos e vegetativos das plantas é de extrema importância para coletas de sementes e produção de mudas. No Cerrado, as interações da biota com o fogo são de grande interesse, já que esses fatores estão intimamente relacionados e podem ser determinantes na manutenção das populações vegetais. Durante 12 meses, foi estudada a fenologia de duas espécies nativas do Cerrado (Enterolobium gummiferum (Mart.) J.F.Macbr. e Caryocar brasiliense Cambess.) em dois regimes de queima: em sítio mantido sob queima bienal modal no mês de agosto (PBM) e em sítio controle, livre de fogo há 14 anos (PC). Os testes de uniformidade foram realizados para verificar a sazonalidade das fases fenológicas. A seleção de modelos por critério de informação de Akaike foi realizada utilizando as variáveis climáticas da área de estudo para identificar quais delas são melhores preditoras das fases fenológicas. A produção de frutos foi estimada nos dois tratamentos. Praticamente, todas as fenofases apresentaram picos de produtividade, com exceção da brotação foliar de C. brasiliense em PC, queda foliar da mesma espécie nos dois tratamentos e E. gummiferum na PC. Em geral, o comportamento fenológico de ambas as espécies não diferiu de outros estudos. Porém, o fogo retardou a troca de folhas e inibiu as fases reprodutivas de C. brasiliense, o que corrobora o comportamento já observado em outras espécies nativas do Cerrado em áreas com incidência de queimadas.

Effect of Environmental Changes on Phenology and Reproductive Biology of Sida cordifolia with Special Reference to the Temperature and Relative Humidity

Impact of environmental factors (temperature and relative humidity) on phenology and reproductive biology of a medicinal plant Sida cordifoliaL.growing at district Agra was studied. The study revealed that phenological events (leaf fall, leaf renewal, flowering and fruiting) varied considerably with the fluctuations in temperature and relative humidity. Flowering was observed throughout the yearwith maximum in the months of FebruaryApril (11.8 �38.3∫C) and August-September (24.4-33.9∫C). Floral biology studies showed that pollen viability, pollenovule ratio and fruit -set percentage was greatly reduced with rise or fall in temperature and rela tive humidity. The maximum pollen fertility (71%), fruit set (70-90%) and pollen-ovule ratio (190:1) was recorded in the month of March when temperature was ranging between 15.1-32.6∫C with 22- 76% RH. With the fall in temperature in the month of January(6.8-17.9∫C) the pollen fertility was reduced to 52%. At the end of April 32.5 -45.3∫C with 16-43% RH, the plants under observation exhibited OriginalResearch Article

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Abstract. The fixation of carbon in tropical forests mainly occurs through the production of wood and leaves, both being the principal components of net primary production. Currently field and satellite observations are independently used to describe the forest carbon cycle, but the link between satellite-derived forest phenology and field-derived forest productivity remains opaque. We used a unique combination of a MODIS enhanced vegetation index (EVI) dataset, a wood production model based on climate data and direct litterfall observations at an intra-annual timescale in order to question the synchronism of leaf and wood production in tropical forests. Even though leaf and wood biomass fluxes had the same range (respectively 2.4 ± 1.4 and 2.2 ± 0.4 Mg C ha−1 yr−1), they occurred separately in time. EVI increased with leaf renewal at the beginning of the dry season, when solar irradiance was at its maximum. At this time, wood production stopped. At the onset of the rainy season, when new leaves were fully mature and water available again, wood production quickly increased to reach its maximum in less than a month, reflecting a change in carbon allocation from short-lived pools (leaves) to long-lived pools (wood). The time lag between peaks of EVI and wood production (109 days) revealed a substantial decoupling between the leaf renewal assumed to be driven by irradiance and the water-driven wood production. Our work is a first attempt to link EVI data, wood production and leaf phenology at a seasonal timescale in a tropical evergreen rainforest and pave the way to develop more sophisticated global carbon cycle models in tropical forests.

밤나무잎의 항주름 효과

본 연구는 노령목의 산림의 경제적 가치를 증진하고자 밤나무 잎에 함유된 물질의 기능성화장품 원료로의 기능을 규명하여 화장품 산업에 적용하기 위하여 천연소재로써의 이용 가능성을 살펴보았다. 항산화능 측정을 위한 실험으로 DPPH radical 소거능과 ABTS cation radical 소거능을 실시하였으며, 양성 대조군으로는 항산화 작용이 있는 것으로 알려진 BHA를 이용하여 밤잎 추출물의 항산화 효과를 비교하였다. 그 결과 아세톤 추출물의 경우 시료 농도에 따라 DPPH radical 및 ABTS radical 소거 증가 정도가 컸으며, 열수 추출물은 10 ug/ml의 농도에서 50% 이상의 소거활성을 나타내었다. 이러한 결과로 미루어 볼 때 밤잎 추출물은 항산화 작용이 높고 피부에서 흔히 일어나는 활성산소에 대한 노화 방지에 도움이 될 것으로 사료된다. 주름개선 효과 측정으로 elastase 저해활성을 측정한 결과 아세톤과 열수 추출물에서는 그 효과가 없었으나 에탄올 추출물 100 ug/ml에서 64.6%의 우수한 elastase 저해활성을 나타내었으며, collagenase 저해활성을 측정한 결과 3가지 추출물은 100 ug/ml에서 열수 추출물 18.0%, 아세톤 추출물 14.3%, 에탄올 추출물 5.3%의 순으로 collagenase 저해활성능을 나타내었으며, 다른 천연물질을 이용한 연구결과와 비교 시 밤잎 추출물은 주름개선에 우수함을 확인 할 수 있었다. 주름개선 원료로의 이용가치가 있을 것으로 보인다. 이상의 연구 결과로 보아 밤잎은 항산화 및 항노화 효소 활성을 갖는 천연소재로서 주름개선 소재로 활용 될 수 있을 것으로 사료되며, 임삼 효능 평가 등의 계속적인 연구를 통해 기능성 화장품 소재로 개발된 가능성이 매우 높다고 사료된다. This research old age chestnut tree that loss function chestnut leaf renewal efficiency enlargement and development of cosmeceutical product by purpose. Chestnut leaf (CL) exhibits numerous pharmacological effect including anti-allergy and anti-microbial properties. However, the anti-wrinkle effect of CL is not completely understood. In this study, to find a possible explanation for the anti-wrinkle effects of CL, we evaluated the effects of CL on radical scavenging activity, elastase inhibition activity and collagenase inhibition activity. CL was extracted with various solvents including water (CLW), 70% ethanol (CLE) and 70% acetone (CLA). The results showed that CLW, CLE, and CLA have the radical scavenging activity. In addition, we showed that CLW, CLE, and CLA have the elastase inhibition activity and collagenase inhibition activity. Consequently, the CL has a potent anti-wrinkle effect and it could be a useful cosmeceutical product for anti-aging purposes.

Biomass and nutrient dynamics in Mediterranean seasonal dimorphic shrubs: Strategies to face environmental constraints

To analyze biomass and nutrient dynamics of Mediterranean seasonal dimorphic shrubs, aboveground biomass (AGB) and belowground biomass (BGB), litterfall (LF), aboveground net annual primary production (ANPP), and nutrient allocation and turnover were estimated in Cistus salviifolius and C. ladanifer, during two years, in southern Portugal. AGB, BGB, LF, and ANPP of C. salviifolius are within the range reported for other seasonal dimorphic plants, while those of C. ladanifer are closer to evergreen sclerophylls. Leaf renewal was higher for C. salviifolius than for C. ladanifer, especially for winter leaves, while root-to-shoot ratio and accumulation of live wood was greater in the latter. The concentrations of N, K, Ca, and Mg were lower in leaves of C. ladanifer than in those of C. salviifolius, suggesting less nutritive requirements for the former. Moreover, leaf nutrient translocation was higher in C. ladanifer than in C. salviifolius. Therefore, C. ladanifer shrubs seem to be more efficient with respect to carbon uptake, even during severe drought, while those of C. salviifolius act as weaker sinks more susceptible to the negative effects of drought. Additionally, C. ladanifer seems to have a competitive advantage in more arid conditions, as a great proportion of its annual nutrient requirement may derive from internal sources.

Environmental drivers of leaf phenology in trees of the tropical species Ficus obtusifolia

Vegetative as well as reproductive phenology of tropical trees frequently occur synchronously at the end of the dry season. It has been repeatedly observed on two individuals of the tropical species Ficus obtusifolia growing in Caracas that they lose their entire foliage in a period of 48 h during the dry season and renew it within the next 72 h. In order to gain knowledge on the mechanisms that govern leaf exchange in F. obtusifolia, we followed in these two individuals the seasonal changes in leaf and fruit phenology, water relations and environmental variables, and in another 25, phenology only. Although foliar exchange was always observed before the rainy season, it also occurred near the end of the rainy season. An increase in leaf turgor potential of mature leaves and a low sap flow velocity coincided with leaf fall. Foliar exchange in all 27 individuals, growing in locations with different elevation and, possibly, access to underground water, was bi-modal and occurred in a period of approximately one month around both equinoxes. The presence of fruits was also bi-modal, occurring after leaf renewal. The sequence of phenological events repeated itself in all the individuals studied, although with inter-annual and individual variations in date of foliar exchange. Leaf fall was independent of leaf water status and significantly correlated with, in decreasing order, day length, minimum air temperature, rainfall, maximum air temperature and total radiation. We conclude that in F. obtusifolia high nocturnal temperature, increasing daytime temperature and radiation, and low cloud cover apparently drove foliar exchange. Day length showed a strong correlation with leaf renewal possibly to due to the significant relationships between day length and environmental variables. Direct effects of day length alone were not evidenced, as foliar exchange took place during a long time-span around the equinoxes.

Carbohydrate remobilization from storage root to leaves after a stress release in sugar beet (Beta vulgaris L.): experimental and modelling approaches

SUMMARYCarbohydrate remobilization from the sugar beet storage root to support leaf regrowth after release from water stress was demonstrated by experimental and modelling approaches. Experimental trials were carried out in northern France in 1994 and 1995 and in southern France in 2005, in conditions that involved a succession of soil moisture stresses and re-hydrations. Drought stress slowed leaf growth and the subsequent release of stress resulted in regrowth. A second trial showed that after total defoliation, sugar beet was able to produce new leaves. It was assumed that this leaf renewal, observed at drought stress release or after defoliation, relied on the possibility of remobilizing carbohydrates from storage roots to above-ground organs. This assumption was tested through a heuristic modelling approach, involving the STICS crop model and its existing sub-model on remobilization. The relevance of these formalizations for sugar beet was tested on the experimental data to validate the plant behaviour concerning remobilization. The model succeeded in reproducing leaf area index (LAI) dynamic trends and particularly leaf re-growth after drought stress release or defoliation, despite an over-estimation of the drought stress effect involving an inaccurate simulation of the changes in LAI. Nevertheless, the model's ability to forecast accurately above-ground and storage root dry weight, as well as trends in LAI dynamics, showed that the assumptions made about remobilization were able to explain sugar beet behaviour.