Physiological response of three wild castor bean (Ricinus communis L.) ecotypes exposed to different levels of substrate moisture

Abstract

Objective: To analyze the morphological and physiological responses of three wild castor bean (Ricinus communis L.) ecotypes with four levels of substrate gravimetric moisture.

Design/methodology/approach: Wild castor bean seeds were collected in the Durango State’s arid zone, Mexico. Three possible ecotypes of seeds were selected according to seed size and shape. A completely randomized greenhouse culture was established with the three wild castor bean ecotypes in substrate with four levels of gravimetric moisture (T1_?= 24±2%; T2_?=20±2%; T3_?= 16±2%; T4_?= 14±2%). Physiological measurements were performed with a photosynthesis meter LICOR (LI-6400XT). Two-way analysis of variance was performed to obtain significant differences among factors and their interactions.

Results: The most striking results are the following: ecotypes 1 and 2 had higher stem height and larger leaves than ecotype 3. The differences in plant growth due to the effect of substrates with gravimetric moisture of 24% and 20% were not significant (p = 0.05). The highest photosynthetic rate corresponds to ecotype 3 (14.77±6.14 ?mol CO₂ m^-2s^-1); however, the differences were not significant among the ecotypes. The differences were mainly determined by the substrate moisture.

Limitations on study/implications: Knowing the castor bean water requirement as a crop allows optimizing the use of water in regions where this resource is scarce.

Findings/conclusions: The castor bean ecotype 1, whose seeds were of great volume, little eccentricity and very round; they are associated with plants with longer and wider stems, with longer and wider leaves. This genotype could be domesticated considering the substrate moisture 24% and 20%.