Producción de clorofila en Pinus pseudostrobus en etapas juveniles bajo diferentes ambientes de desarrollo

limiting the amount of sun radiation reduces photosynthetic activity, causing stress and morphological and/or physiological changes in plant development. this study analyzed the stress effect caused by two levels of competition in pinus pseudostrobus lindl half-sib families: high inter-family (environment ii) and high intra-family (environment iii) competition, compared with a low level of competition (environment i). total chlorophyll, chlorophyll-a, and chlorophyll-b content, plus the chlorophyll a/b ratio, were quantified as an indicator of stress level in 10-month-old plants using the barnes method. plants were established in a common garden test under a split-plot design with four replications and three individuals per plot. total chlorophyll was significantly higher (p<0.05) in environment i; no differences (p>0.05) were observed between the other competition environments. a separate analysis of chlorophylls showed lower chlorophyll-a content in plants surrounded by genetically-similar plants (environment iii) as opposed to genetically-different ones (environment ii); conversely, chlorophyll-b content was higher in genetically-similar plants (environment iii). in conclusion, intra-genotypic competition was generally stronger than inter-genotypic competition, under high levels of stress.