Alocação de biomassa e indicadores de crescimento para a avaliação da qualidade de mudas de espécies florestais nativas

Procedures and methodologies for evaluating the quality and uniformity of seedlings are essential for homogenizing lots in forest nurseries and successful planting for reforestation. A study was made in order to evaluate the correlations between the allocation of biomass and the Dickson Quality Index (IQD) for seedlings from six native tree species of the Atlantic Forest as well as to select quality indicators that most affect the IQD and which can be used in a practical and precise fashion for the evaluation of native forest seedlings. Seedlings from six tropical forest species were used: Calophyllum brasiliense, Eriotheca macrophylla, Inga laurina, Psidium cattleyanum, Roupala montana and Sloanea obtusifolia. The following characteristics were evaluated: dry leaf (MSF), dry stem (MSC) and dry root (MSR) mass, as well as the aerial part height (H) and the stem diameter (D). Based on these variables, the following calculations were made: ratios of root (RMR), stem (RMC) and leaf (RMF) mass, as well as the total dry mass (MST), that of the aerial part (MSPA), the ratio of the aerial part dry mass to the dry root mass (MSPA/MSR), and that of the aerial part height to the stem diameter (H/D), and the IQD. The results were analyzed via correlation analyses. Based on the conditions of this study it is possible to conclude that: (a) the differences between the average IQD values of the species studied were not explained by the allocation pattern of biomass characterizing each species; (b) the MSR, MST and the D are the best variables for predicting the IQD of the seedlings from the forest species analyzed in this study; and (c) because it is a non-destructive method, D can be considered the best practical indicator for estimating IQD values for Atlantic Forest seedling species lots.Procedimentos e metodologias que permitam avaliar a qualidade e a uniformidade das mudas são fundamentais para a homogeneização dos lotes em viveiros florestais e o sucesso dos plantios para reflorestamento. Foi conduzido um estudo com o objetivo de avaliar as correlações entre a alocação de biomassa e o índice de qualidade de Dickson (IQD) para mudas de seis espécies arbóreas nativas da Mata Atlântica, bem como selecionar indicadores de qualidade que mais influenciam o IQD e que possam ser utilizados de maneira prática e precisa para a avaliação da qualidade de mudas florestais nativas. Foram utilizadas mudas de seis espécies arbóreas tropicais: Calophyllum brasiliense, Eriotheca macrophylla, Inga laurina, Psidium cattleyanum, Roupala montana e Sloanea obtusifolia. Foram avaliados a massa seca de folhas (MSF), os caules (MSC) e as raízes (MSR), além da altura da parte aérea (H) e diâmetro do coleto (D). A partir dessas variáveis, foram calculadas as razões de massa de raízes (RMR), caules (RMC) e folhas (RMF), além da massa seca total (MST), a massa seca da parte aérea (MSPA), a razão de massa seca da parte aérea por massa seca de raízes (MSPA/MSR), a razão altura da parte aérea por diâmetro do coleto (H/D) e o IQD. Os resultados foram analisados mediante análises de correlação. Com base nas condições em que este estudo foi realizado é possível concluir que: (a) as diferenças entre os valores médios do IQD das espécies estudadas não foram explicadas pelo padrão de alocação de biomassa característico de cada espécie; (b) a MSR, a MST e o D são as melhores variáveis para predizer o comportamento do IQD das mudas das espécies florestais analisadas neste estudo; e (c) pelo fato de ser um método não destrutivo, o D pode ser considerado como o melhor indicador prático para estimar os valores de IQD de lotes de mudas de espécies florestais da Mata Atlântica

Predictions of chlorophyll concentrations in the leaves of seedlings of two congeneric tropical trees from RGB digital image components

The segmentation of digital images in red, green and blue (RGB) components is a low-cost method for monitoring leaf chlorophyll concentrations and seedling quality. The two congeneric species, Cariniana legalis and C. estrellensis, are distinguished based on differences in bark texture and the colour of their new leaves. We compared indices based on leaf colour segmentation in RGB to predict total chlorophyll concentrations (Chlt) in the leaves of seedlings of these two species. Mature leaves were digitalised in a flatbed scanner and segmented in red (R), green (G) and blue (B). The relationships between the three RGB indices and Chlt were tested. Additionally, we calculated the anthocyanin content-chroma basic (ACcb). The mean value of ACcb was significantly higher in C. legalis than in C. estrellensis, demonstrating a higher anthocyanin concentration in C. legalis leaves. Based on the highest coefficients of determination (R2) and lowest prediction errors (PE), for all indices, the best results were obtained for C. estrellensis. The presence of anthocyanins in the leaves of C. legalis and the limitation of the RGB colour segmentation indices for separating all leaf pigments might be the main causes of the differences in Chlt prediction in the leaves of these two congeneric tree species

Infuence of soil characteristics on physiological and growth responses of Cytharexyllum myrianthum Cham. (Verbenaceae) to fooding

The success of watershed riparian forest restoration programs can be afected by the selection of plant species tolerant to fooding and soil types that occur along water courses. We evaluated physiological and growth responses of Cytharexyllum myrianthum seedlings to fooding in three diferent soil types representative of the Almada River Watershed (ARW), southern Bahia, Brazil. The soils selected, based on the relative abundance and importance in the ARW, were: Luvisol, Argisol, and Spodosol. After 35 days of fooding, the Argisol had the lowest and the Spodosol had the highest reduction–oxidation (redox) potential (Eh). After 35 days of fooding, the Luvisol had higher pH and electrical conductivity (Ec) than the other soils. Stomatal conductance (gs) and net photosynthesis (A) signifcantly declined in all soil types after 7 days of fooding. After that period, morphological changes characteristic of food-tolerant plants, such as lenticel hypertrophy and adventitious root formation, were observed in all fooded plants. Following the morphological changes, gs and A in fooded plants increased to values close to those of the non-fooded plants. The highest relative growth rates based on mass (RGRm) and net assimilation rates (NAR) for the non-fooded plants were observed in the Argisol. After 35 days of fooding, no signifcant diferences in RGRm or NAR were observed between non-fooded and fooded plants in the Luvisol, but large signifcant decreases in RGRm and NAR were observed for the fooded plants in the Spodosol. Our results demonstrated that the ability of seedlings of the same species to acclimate to fooded soil conditions difers among soil types. Therefore, the characteristics of soils present in a watershed should be considered when selecting tree species for the reforestation of riparian forests.El éxito de los programas de restauración de bosques ribereños de cuencas hidrográficas puede verse afectado por la selección de especies de plantas tolerantes a la alimentación y los tipos de suelo que se encuentran a lo largo de los cursos de agua. Evaluamos las respuestas fisiológicas y de crecimiento de plántulas de Cytharexyllum myrianthum a la alimentación en tres diferentes tipos de suelo representativos de la Cuenca del Río Almada (ARW), sur de Bahía, Brasil. Los suelos seleccionados, en base a la relativa abundancia e importancia en el ARW, fueron: Luvisol, Argisol y Spodosol. Después de 35 días de alimentación, el Argisol tuvo el menor y el Spodosol el mayor potencial de reducción-oxidación (redox) (Eh). Después de 35 días de alimentación, el Luvisol tenía un pH y una conductividad eléctrica (Ec) más altos que los otros suelos. La conductancia estomática (gs) y la fotosíntesis neta (A) disminuyeron significativamente en todos los tipos de suelo después de 7 días de alimentación. Después de ese período, se observaron cambios morfológicos característicos de las plantas tolerantes a los alimentos, como la hipertrofia de las lenticelas y la formación de raíces adventicias, en todas las plantas inundadas. A raíz de los cambios morfológicos, gs y A en plantas sembradas aumentaron a valores cercanos a los de las plantas no sembradas. Las tasas de crecimiento relativo más altas basadas en la masa (RGRm) y las tasas de asimilación neta (NAR) para las plantas no alimentadas se observaron en Argisol. Después de 35 días de alimentación, no se observaron diferencias significativas en RGRm o NAR entre las plantas no alimentadas y alimentadas en Luvisol, pero se observaron grandes disminuciones significativas en RGRm y NAR para las plantas alimentadas en Spodosol. Nuestros resultados demostraron que la capacidad de las plántulas de la misma especie para aclimatarse a las condiciones del suelo inundado difiere entre los tipos de suelo. Por lo tanto, las características de los suelos presentes en una cuenca deben ser consideradas al seleccionar especies de árboles para la reforestación de bosques ribereños.Universidade Estadual de Santa Cruz, BrasilUniversidade Federal do Sul da Bahia, BrasilUniversidad de Florida, Estados UnidosUniversidad Nacional, Costa RicaEscuela de Ciencias Biológica

Screening of cacao clones for drought tolerance by assessing predawn leaf water potential, growth, and leaf gas exchange

Drought in cacao-producing regions worldwide is causing a decrease in yield and, in severe cases, leading to plant death. This primarily affects small farmers who lack sufficient financial resources or water availability to irrigate their plantations. This study aimed to test 83 cacao clonal genotypes for drought tolerance by evaluating their physiological and morphological features. These genotypes, referred to as drought-tolerant cacao (DTC) genotypes, were selected through mass selection from regions of Bahia, Brazil, severely affected by prolonged droughts. Seedlings of the DTC clonal genotypes and two control clones (CCN 51- drought-intolerant and CEPEC 2002 – drought-tolerant) were obtained from rooted cuttings of plagiotropic branches and evaluated under greenhouse conditions. Three experiments (EXP 1, 2, and 3) were conducted using a randomized block design, with three replications each and two plants per replication of each clonal genotype to test for drought tolerance. Data analyses were conducted using univariate and multivariate statistical analysis. DTC and control clones were subjected to varying soil moisture contents [70, 60, 50, 40, and 30 % of field capacity (FC)] and their controls (maintained close to 100 % of FC) for approximately 40 to 60 days. The results revealed significant statistical differences in growth variables before the plants were subjected to drought. They were categorized based on vigor into three, four, and three groups for EXP 1, 2, and 3, respectively during cluster analysis. DTC and control clones subjected to drought (70, 60, 50, 40, and 30 % of FC) exhibited significant statistical differences in physiological traits compared to the traits of their respective controls (100 % of FC). However, plant growth remained largely unchanged under drought stress (30 or 40 % of FC). DTC clonal genotypes 15, 17, 23, 41, 61, 66, 90, 91, 92, and 93 were more efficient in maintaining net photosynthesis (A) with decreases in soil moisture, showing greater changes only at 40 % of FC. DTC clonal genotypes 14, 32, 41, 61, 69, 70, 88, 89, 92, 95, and 108 maintained stomatal conductance (gs) values similar to those of their controls. Twenty-three DTC clonal genotypes maintained values of A, gs, E, Ci, A/gs, and A/E close to their respective controls, suggesting that these genotypes present features for drought tolerance