Studies on achene germination, transplantability, salinity tolerance, and cultivation of gumweed ( Grindelia camporum) in hot and semi-arid conditions

Abstract

The study reports achene germination under varying laboratory conditions, transplantability, survival of seedlings in saline soils, and a field cultivation trial of Grindelia camporum (gumweed) in a semi-arid and hot climate. Achenes placed under a thin layer of soil, on wet filter paper, or in water, at ambient temperature and a diffuse daylight/night cycle germinated at 75%, 69% and 65% respectively. In total dark at ambient temperature compared with 8°C, the achene germination in water was 41% and 48%, respectively. During the 2-step procedure of a cool pretreatment at 8°C in the dark for 4 days followed by a shift to ambient temperature and diffuse daylight/night cycle, however, germination rose to 74%. Achenes germinated in water or on wet filter paper survived well when transplanted to soil whereas those germinated under a thin layer of soil, when uprooted, did not withstand transplantation. Survival of seedlings in saline soils having electrical conductivity of 4, 8, 12 and 16 mmho/cm was, respectively, 31%, 18%, 7% and zero as compared with 91% in the normal soil (3 mmho/cm). During the growing season of 363 days, two crops were harvested yielding 1.36 kg m −2 year −1 biomass and 128 g m −2 year −1 crude resin.