Production of floral morphs in cleistogamous Ruellia brevifolia (Pohl) C. Ezcurra (Acanthaceae) at different levels of water availability

Abstract

In this study we investigated whether the production of cleistogamous (CL) and chasmogamous (CH) floral morphs in Ruellia brevifolia is affected by water availability. To this end, the effects of two water levels were tested on plants grown in a greenhouse: soil at 100% water-holding capacity (WHC) (moist soil) and at 50% WHC (water scarcity). Additionally, we investigated fruit and seed production in plants at these two levels of water availability and evaluated whether the drought stress interferes with vegetative growth. The production of floral morphs depended on water availability: plants in moist soil produced only CH morphs and water-stressed plants produced only CL morphs. Fruit production was higher at the higher level of water availability (30.5 ± 28.20 fruits/plant at 100% WHC versus 9 ± 6.04 fruits/plant at 50% WHC; t = 4.384; P < 0.01). The mean number of seeds produced by CH and CL morphs were, respectively, 5.93 ± 2.24 and 8.17 ± 2.07 seeds/fruit (t = - 3.304; P < 0.01). Although CL morphs produced a greater number of seeds, the total seed production per plant was higher in plants at 100% WHC (180.86 seeds/plant in CH morphs versus 73.53 seeds/plant in CL morphs of plants in soil at 100% and 50% WHC, respectively; t = - 2.759; P < 0.01).  The plants in soil at 100% WHC were taller (0.48 m ± 0.07) in relation to plants in soil at 50% WHC (0.24 m ± 0.04) (t = 1.781; P < 0.01). This study provides new information about the sexual reproductive strategy of R. brevifolia, indicating that the main factor inducing cleistogamy is drought stress.