Physiological comparison of root trainer and polybag plants of Hevea brasiliensis

Abstract

The physiology of   root trainer plants in comparison to polybag plants of two popular Hevea clones,   RRII 105 and RRII 430 was studied. Dry matter partitioning and physiological   parameters like leaf water potential, relative water content, chlorophyll   content, PS II activity and photosynthetic efficiency were studied in root   trainer and polybag plants and compared. Root trainer plants had only 55 per   cent less biomass than polybag plants at two whorled stage. No variation was   noticed in water relations among the poly bag and root trainer plants. Total   chlorophyll content and chlorophyll a/b ratio were higher in polybag   plants than root trainer plants of both clones. Polybag plants showed higher   light saturation point when gas exchange was measured at different   photosynthetic photon flux densities. Though there was no variation in   effective quantum yield (Φ PSII), the root trainer plants of RRII 105 showed   more excess electrons (J*) at higher light intensities. Photosystem II   activity and photosynthetic carbon assimilation rates were less in root   trainer plants under open and shaded conditions. The results indicated that   the root confinement in root trainer plants has significant effect on the   physiology of plants. The reduction in plant biomass and other physiological   traits in root trainer plants can be attributed to the limited space in the   container, limiting further root growth, which otherwise is beneficial for   giving a priming effect as long as the plant remains in the container.   Further studies are needed to quantify this ‘stress factor’ in root trainer   plants and its implications in growth and establishment of plants in the   field.