Effect of water stress on the growth and development of feathertop Rhodes grass (Chloris virgata)

Abstract

Anecdotal observations suggest that feathertop Rhodes grass (Chloris virgata) matures earlier when growing under water-stressed conditions. To investigate this claim, field capacities (FCs) aligning with severe (15, 25, 37.5% FC), moderate (50, 62.5, 75% FC) and no stress (100% FC) were imposed on plants in two consecutive growth cabinet experiments. The objectives of the study were to investigate if the growth and development parameters of feathertop, along with seed production and viability were impacted by FC. Under severe stress, feathertop tillered at 15% FC before dying, whereas plants at 25% FC matured and produced viable seed. Tiller production in plants grown at 37.5% FC and above were not significantly different and ranged from 18 to 22 tillers/plant before panicle initiation. The greatest dry weight biomass (8.20 g/plant) occurred with 75% FC, but this was not significantly different from biomass at 100% FC (7.44 g/plant). Plants grown under these conditions produced significantly heavier plants than at lower FCs (0.12 to 6.2 g/plant). Feathertop grown under severe stress took longer to mature; between 110 and 83 days (25% and 37.5% FC respectively) compared to between 58 and 77 days for plants grown at 50% FC and above. While plants grown at 25 and 37.5% FC remained vegetative for longer, once panicles were produced, they matured within 7 - 13 days, comparative to other FCs (10 - 13 days). Plants grown under severe stress produced between 1274 to 7351 seeds/plant (25% and 37.5% FC respectively) compared to seed production of 8891 seeds/plant (50% FC) and 15776 seeds/plant (75% FC). This research showed that soil water availability had a significant impact on the growth and development of feathertop Rhodes grass. In soils with a field capacity as low as 25% feathertop can survive and produce significant quantities of seed which return to the seed bank.