Resumen El objetivo de este estudio consistió en conocer el comportamiento de Hevea brasiliensis en lo que se refiere al desempeño fotosintético, en las regiones caucheras del nordeste y el Bajo Cauca (Antioquia, Colombia), como base para futuros estudios de desempeño clonal entre ambientes. El intercambio de gases se cuantificó mediante un analizador infrarrojo de gases portátil, y en las variables fotosintéticas para los siete clones se calculó un valor medio, a partir del cual se estimó el área bajo la curva. El máximo valor de fotosíntesis se alcanzó a las 8:00 en San Roque (10,97 μmol [CO2] m-2s-1), y 9:00 en Caucasia (7,84 μmol [CO2] m-2s-1). La transpiración máxima fue de 3,55 mmol [H2O] m-2s-1 en San Roque, y de 5,16 mmol [H2O] m-2s-1 en Caucasia, mientras que la conductancia estomática máxima fue de 0,18 mol [CO2] m-2s-1 y de 0,16 mol [CO2] m-2s-1, respectivamente. Las plantas de caucho en Caucasia presentaron una mayor tasa de asimilación neta acumulada (271.934 μmol [CO2] m-2día-1), superando los 226.287 μmol [CO2] m-2día-1 de San Roque, lo que representa una diferencia de 45.647,52 μmol [CO2] 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. Por lo tanto, en lo que respecta al intercambio gaseoso y al uso de la energía lumínica, Hevea brasiliensis presentó una mayor adaptación ambiental en San Roque.

Abstract 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.

Resumo O objetivo deste estudo consistiu em conhecer o comportamento de Hevea brasiliensis no que se refere ao desempenho fotossintético, nas regiões borracheiras do nordeste e do Baixo Cauca (Antioquia, Colômbia), como base para futuros estudos de desempenho clonal entre ambientes. O intercâmbio de gases foi quantificado mediante um analisador infravermelho de gases portátil, e nas variáveis fotossintéticas para os sete clones foi calculado um valor médio, a partir do qual foi estimada a área sob a curva. O máximo valor de fotossíntese foi alcançado às 8:00 em San Roque (10,97 μmol [CO2] m-2s-1), e 9:00 em Caucasia (7,84 μmol [CO2] m-2s-1). A transpiração máxima foi de 3,55 mmol [H2O] m-2s-1 em San Roque, e de 5,16 mmol [H2O] m-2s-1 em Caucasia, enquanto a condutância estomática máxima foi de 0,18 mol [CO2] m-2s-1 e de 0,16 mol [CO2] m-2s-1, respectivamente. As plantas de borracha em Caucasia apresentaram maior taxa de assimilação líquida acumulada (271.934 μmol [CO2] m-2dia-1), superando os 226.287 μmol [CO2] m-2dia-1 de San Roque, o que representa uma diferença de 45.647,52 μmol [CO2] m-2dia-1. A maior acumulação de carbono com menor investimento de energia lumínica (697.638 μmol [CO2] μmol [fóton]-1dia-1) obteve-se em San Roque. Portanto, no que se refere ao intercâmbio gasoso e ao uso da energia lumínica, H. brasiliensis apresentou maior adaptação ambiental em San Roque.

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 cm2 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.

La investigación se desarrolló en la Estación Experimental San Antonio (EESA) de Cenicaña ubicada en el corregimiento de San Antonio de los Caballeros (Florida, Valle del Cauca). Se realizaron dos experimentos denominados condición húmeda (con lisímetros para el manejo artificial del nivel freático) y condición semiseca (en campo), utilizando un diseño de bloques completos al azar con tres repeticiones. Se evaluó el aerénquima presente en las raíces fibrosas de 13 variedades de caña de azúcar (Saccharum spp.) a 4, 6 y 8 meses después de la siembra y las variables agronómicas altura de planta, diámetro de tallo, población de tallos, peso de tallos por parcela y producción de sacarosa por parcela al momento de la cosecha. Se encontró una respuesta diferencial entre condiciones a causa de la falta de oxígeno (hipoxia). En condiciones húmedas el aerénquima ocupó 55% del área total de los tejidos en la raíz, sin diferencias estadísticas entre variedades; mientras que en condiciones semisecas sólo ocupó 33%. En ambas condiciones, el aerénquima no mostró asociación con las variables agronómicas evaluadas, no obstante la variedad CC01-1884 presentó el mejor comportamiento agronómico.

The research was developed at the experiment station San Antonio (EESA) of Cenicaña located in the village of San Antonio de los Caballeros (Florida, Cauca Valley). Two experiments were conducted one on semi-dry conditions and another on wet conditions, each one with a design of a randomized complete block with three replications. The aerenchyma observed in the fibrous roots of 13 varieties of sugarcane was evaluated (Saccharum spp) by 4, 6 and 8 months after planting. Agronomic variables as height, diameter, population, stalk weight of total plot, sucrose (% cane) and yield of sucrose per plot were evaluated at harvesting time. It was found that there was a differential response between environments because of the lack of oxygen (hypoxia) in soil. On wet conditions, the aerenchyma occupied 55% of the total area in the root tissues although did not show statistical differences between varieties, whereas the opposite occurred on semi-dry conditions where only occupied 33%. The aerenchyma was not associated with any agronomic traits evaluated. The variety CC 01-1884 had the best agronomic performance in the evaluations.