Allometric models based on measurements of single leaf dimensions or a combination there are useful tools for determining individual leaf area (LA) because they are non-destructive, precise, simple and economical methods. The present study was carried out at the Central Station Naranjal of Cenicafé, located in the Department of Caldas (Colombia), four models were defined using the variables length (L) and/or width (W) to estimate LA in coffee leaves of the Castillo  variety (Coffea arabica L.). Estimation of regression coefficients was performed using information recorded from 6,441 leaves (group 1), and their validation was performed using records from another 992 leaves (group 2). Leaves were collected from all strata of the canopy and ranged from 0.76 to 140 cm 2 in LA. In addition to exhibiting coefficients of variation differing from zero based on t-tests at 1%, the evaluated models possess coefficients of determination between 0.93 and 0.99. Four expressions have developed and adjusted to estimate leaf area in individual leaves, based on the measurement of simple variables and non-destructive.

El objetivo fue conocer el comportamiento de Hevea brasiliensis a partir del desempeño fotosintético en las regiones caucheras de Nordeste y Bajo Cauca de Antioquia (Colombia) como base para futuros estudios de desempeño clonal entre ambientes. Se cuantificó el intercambio de gases mediante un analizador infrarrojo de gases portátil; para las variables fotosintéticas se calculó un valor medio para los siete clones, a partir del cual se estimó el área bajo la curva. El máximo valor de fotosíntesis se alcanzó a las 8 horas en San Roque (10,97 µmol [CO2] m-2s-1) y 9 horas en Caucasia (7,84 µmol [CO2] m-2s-1). La transpiración máxima fue 3,55 mmol [H2O] m-2s-1 en el municipio de San Roque y 5,16 mmol [H2O] m-2s-1 en Caucasia, mientras que la conductancia estomática máxima fue 0,18 mol [CO2] m-2s-1 y 0,16 mol [CO2] m-2s-1 respectivamente para cada localidad. Las plantas de caucho en Caucasia presentaron mayor tasa de asimilación neta acumulada 271.934 µmol [CO2] m-2día-1, superando los 226.287 µmol [CO2] m-2día-1 en San Roque y, representado en una diferencia de 45.647,52 [CO2] µmol m-2día-1. La mayor acumulación de carbono con menor inversión de energía lumínica (697.638 µmol [CO2] µmol fotón-1día-1) se obtuvo en San Roque. Hevea brasiliensis presentó una mayor adaptación ambiental con respecto al intercambio gaseoso y el uso de la energía lumínica en San Roque.

The cultivation of cocoa (Theobroma cacao L.) under agroforestry systems, generates beneficial environmental conditions for cocoa crop physiology. An experiment was conducted to evaluate the effect of shade trees (Spanish elm trees - Cordia alliodora (Ruiz & Pavon) Oken) planted along with cocoa (clone CCN51) under an agroforestry system on cocoa’s gas exchange parameters regarding the reduction of the light intensity over the cocoa-leaf canopy. The experiment was developed in the Centro de Investigación el Nus - Agrosavia, located in the municipality of San Roque, Antioquia. The experimental design used was a randomized complete block design for the cocoa planting distances from the first row of Spanish elm trees interfacing with the cocoa plantation (4 m, 7 m, 10 m, 13 m). The statistical analysis was performed by estimating the area under the curve (AUC) of each variable, using the trapezoid equation of the statistical environment SAS® 9.4, an analysis of variances was performed to determine if there were statistical differences between treatments, and Tukey’s test at 5% probability was used to estimated statistical differences between means. There were significant differences in the treatments regarding the net photosynthetic rate (A), stomatal conductance (gs), and transpiration rate (E). The highest values of gas exchange parameters were found in the plants located 13 m from elm trees, while the lowest values were presented at 4 m. Plants at 7 m and 10 m always showed intermediate values for all gas exchange parameters. In the same sense, plants at 13 m had a higher radiation use efficiency (RUE) compared to plants at 4 m. The arboreal component modified the environmental conditions on cocoa trees regarding its distribution, generating a differential response to the physiological behavior of cocoa plants.

The knowledge of the defoliation-refoliation process in rubber cultivation allows the development of management strategies in the production system to improve rubber yield. The objective of this study was to determine the intensity and duration of defoliation-refoliation of rubber clones FX 3864, IAN 710 and IAN 873 in the municipality of Tarazá and the FX 3864 and IAN 873 clones in the municipality of Nechí (northwestern Colombia). From October 2015 to June 2016, the measurements of the necromass were carried out in each location for each clone. The light environment was quantified, employing the hemispheric photographs technique to estimate canopy openness percentage (CO) and leaf area index. The assessed weeks were grouped by Principal Component Analysis (PCA) based on the original phenology and climatic variables. The defoliation-refoliation process was analyzed descriptively using graphical representations of the trend for the phenological variables that best described this process. The relationship between climatic and phenological variables in the period evaluated was evidenced; the rainfall was the most critical climatic characteristic in the induction of the defoliation process. The leaf area index was reduced to a minimum value in February, with values of 0.52 for IAN 710 clone in Tarazá, and 0.64 for the IAN 873 clone in Nechí, which corresponded to the highest defoliation stage in both locations. The refoliation period was short (4 to 6 weeks) and occurred during the dry season for all the clones in both places.

The aim of this study was to determine the behavior of the rubber plant Hevea brasiliensis regarding its photosynthetic performance in the rubber producer regions in Nordeste and Bajo Cauca, in the department of Antioquia, Colombia, as a baseline for future clonal performance studies among environments. Gas exchange was recorded using a portable infrared gas analyzer, and for the photosynthetic parameters for seven genotypes (clones) a medium value was calculated and was later used to estimate the area under the curve. The maximum photosynthetic value was reached at 8:00 hours in San Roque (10.97 µmol [CO2] m-2s-1) and at 9:00 hours in Caucasia (7.84 µmol [CO2] m-2s-1). Maximum transpiration was 3.55 mmol [H2O] m-2s-1 in San Roque and 5.16 mmol [H2O] m-2s-1 in Caucasia, while the maximum stomatal conductance was 0.18 mol [CO2] m-2s-1 and 0.16 mol [CO2] m-2s-1 in San Roque and Caucasia, respectively. The rubber plants in Caucasia had a higher accumulated net assimilation rate (271,934 µmol [CO2] m-2day-1) than what was found in San Roque (226,287 µmol [CO2] m-2day-1), showing a difference of 45.647,52 µmol [CO2] m-2day-1. The highest carbon accumulation with the lowest light energy investment (697,638 µmol [CO2] µmol [photon]-1day1) was found in San Roque. Therefore, regarding gas exchange and the use of light energy Hevea brasiliensis showed greater environmental adaptation in San Roque.

especie y su relación con las condiciones ambientales donde se desarrolla, las cuales pueden ser modificadas por los componentes que integran un sistema agroforestal. Con el objetivo de comparar las variables de intercambio gaseoso en los clones de cacao (Theobroma cacao) TCS01, TCS06, TCS13, TCS19 y CCN51 plantados en un sistema agroforestal con árboles de abarco (Cariniana pyriformis Miers), se evaluó la fotosíntesis neta (A), la conductancia estomática (gs) y la transpiración (E) en una hoja de cacao joven completamente desarrollada en seis plantas de cada uno de los clones, cada hora entre las 08:00 y 17:00 horas (n = 5000) por cinco días. Con los datos de intercambio gaseoso se estimaron las áreas bajo la curva (ABC) para cada variable con base en la sumatoria de las áreas trapezoidales fraccionadas. Los datos de las ABC fueron sometidos a análisis de varianza y los tratamientos comparados por la prueba de medias Tukey (P ≤ 0.05). El clon TCS06 presentó la mayor fotosíntesis neta acumulada con un valor de 137.000 μmol CO2 m-2 día-1, superando a los clones TCS19 y TCS01. Se registraron valores máximos de A = 6.6 μmol CO2 m2 s-1 (TCS06), gs = 0.12 mmol CO2 m-2 s-1 (CCN51) y E = 4.52 mmol H2O m-2 s-1 (CCN51). Los clones TC606 y TCS01 sobresalieron con respecto a TCS13, TCS19 y CCN51. El clon TCS06 presentó la mayor tasa fotosintética en función de la integral diaria del intercambio gaseoso en comparación con TCS19 y TCS13. El CCN51 fue el clon que requirió los mayores valores de radiación fotosintéticamente activa para lograr la máxima actividad fotosintética.

Los modelos que describen relaciones alométricas, basados en el conteo de hojas, son métodos no destructivos, fáciles y económicos para estimar el área foliar en árboles. Con este propósito se realizaron mediciones del área foliar, censando las hojas en varios árboles de café Variedad Castillo® (Coffea arabica L.) de diferentes edades, estableciendo y validando la relación entre el área foliar de la rama y el número de hojas en ella, a través de una regresión lineal simple, con coeficientes de regresión diferentes de cero, según prueba de t, al 5%. Posteriormente, se evaluó la estimación del área foliar a nivel de árbol con respecto a los valores observados. Además, con la información registrada se determinó el número de ramas por árbol en las cuales deben contarse el número de hojas, para estimar el área foliar del árbol, con un error menor del 20%, y se estableció una primera relación entre el área foliar y la producción en café cereza verde, con un coeficiente de determinación del 78,3%.

El presente provee información básica a nivel departamental del desempeño sectorial, sus vínculos con la orientación de la ciencia, la tecnología, la innovación y las demandas del sector sobre conocimiento técnico para focalizar la investigación publica, articular capacidades, aunar esfuerzos para superar problemas productivos, mejorar la competitividad y aprovechar oportunidades del mercado en distintas cadenas de productividad priorizadas en el departamento.