Effects of Drought and Growth Media on Lentil Growth Characteristics

Abstract

Lentil (Lens culinaris Medik.) is usually grown in regions where lack of moisture limits its production. Drought can be a major limitation to lentil production in the Palliser triangle where annual precipitation is about 300 mm. Root growth and distribution play an important role in crop productivity under dry conditions, enabling plants to access water. The goal of this research was to develop appropriate methods for studying the effects of drought on root and shoot characteristics of a diverse set of lentil genotypes grown in environmentally controlled growth chambers. Two cultivated L. culinaris (Eston and CDC Greenstar) and 5 wild lentil genotypes (L. orientalis IG 72611, L. tomentosus IG 72805, L. odemensis IG 72623, L. lamottei IG 110813, and L. ervoides L01-827A) were grown in Sunshine Mix # 4 (SSM4) and Greens Grade® (GG) media under fully-watered and drought conditions in two growth chambers. SSM4 is a commonly used growth medium at U of S, and GG is known to provide rapid separation of root samples from the growth medium with minimum damage to root systems. Shoot and root characteristics of the genotypes were compared after growing them separately in SSM4 and GG to identify the best growth medium and to compare morphology of different lentil genotypes. The influence of drought on root and shoot characteristics of the lentil genotypes was investigated separately in each growth medium. Shoot traits measured included plant height, number of nodes on the main stem, total number of leaflets per plant, SPAD value, shoot biomass and transpiration rate. Root traits measured were number of nodules, root biomass, root/shoot ratio, total root length, total root surface area, length density, average diameter, volume, and total number of tips and forks. SSM4 was found to be a superior growth medium relative to GG. Most genotypes had significantly higher plant height, SPAD, shoot biomass, transpiration rate and nodule number when grown in SSM4. This was likely associated with higher N concentration in SSM4 compared to GG. It seemed that N mineralization (conversion of organic to inorganic plant available form) in SSM4 was greater relative to GG. Lens culinaris Eston had the highest shoot biomass compared to all other lentil genotypes when grown in SSM4 under both fully-watered and drought conditions. However, reduction in root biomass of L. culinaris Eston under dry conditions was significantly higher compared to wild lentil genotypes, an indicator that cultivated lentil genotypes experienced drought stress. The lowest reduction in root biomass was observed in L. odemensis IG 72623, which makes this genotype a potential candidate for introgression of root characteristics into cultivated lentil genotypes. Drought caused reduction in number of nodes, total number of leaflets and transpiration rate. Drought also reduced root/shoot ratio in cultivated lentil genotypes. No significant difference in root/shoot ratio of wild genotypes was observed between fully-watered and drought conditions, with the exception of L. tomentosus IG 72805 and L. lamottei IG 110813, which showed significantly greater root/shoot ratio under dry conditions.