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.

Annual defoliation and refoliation cycles that occur in rubber trees after 5 years of age have a strong interaction with foliar diseases attacks. The rubber phenology was studied in the eastern plains of Colombia, in the municipality of Puerto López, department of Meta, where variables such as foliar density, percentage of leaves in stages A, B, C and D and flowering density were evaluated in clones IAN 873, FX 3864 and RRIM 600, between August 2016 and September 2018. All three clones showed a foliar density higher than 80% with leaves in stage D, between March and December (weeks 12–50 of the year). The defoliation started in the last weeks of the year, with the beginning of the dry season. The refoliation extended until mid-March (week 11) in 2017, and until February (week 6) in 2018. The presence of leaves in stages A, B and C during 8–13 weeks was observed at the plantation level, according to the clone and the evaluation year. The duration of the refoliation per tree was on average 6.73 ± 0.22 weeks in 2017 and 4.42 ± 0.39 weeks in 2018. Flowering coincided with refoliation, during a period of negative water balance and high solar radiation. Expansion of inflorescences was observed in the first weeks of the year between January and March, with the absence of reproductive development when the crop was dominated by leaves in stage D.

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.

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