Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/1998
Publication Date: N/A
Interpretive Summary: Roots provide the life line between the plant and the soil. They play a major role in transporting water and nutrients for survival. The number of roots, rooting patterns and rooting depth are important characteristics needed for sunflower to survive. It is also important to know at what temperature root growth is maximum. The problem is that we do not know what tthe response of sunflower roots are to soil temperature. We have a large pool of germplasm available from which to select for rooting character- istics. This pool includes the wild relatives of the sunflower which have variable rooting systems which allow them to survive in unique environments Two cultivated hybrids and six interspecific sunflower genotypes were evaluated in the laboratory for root growth patterns and their response to soil temperature. Maximum root growth for sunflower occurs at about 85 degrees F. Very little root growth takes place at 50-60 degrees F, while no ogrowth occurred at 100 degrees F. Root growth appears to be genotype specific and temperature specific within genotype. The specific response may account for the adaptability of some hybrids and interspecific genotypes to different environmental conditions. Sufficient variability appears to exist in the sunflower germplasm for root growth, but the next step will be to correlate the rooting responses in the laboratory to rooting responses in the field.
Technical Abstract: There are numerous environmental factors that can influence the growth and function of plant root systems such as temperature. While we have some information about rooting depth in sunflower, we lack information about early root growth and their response to soil temperature. The wild progen- itors of the crop species are potential sources for enhancing the rooting system of sunflower. Root growth characteristics of seedlings of six genetically diverse sunflower (Helianthus ssp.) genotypes and two cultivat- ed hybrids were evaluated during a 10-day period to determine the influence of soil temperature varying from 10 to 40 deg. C in 5 deg. increments on root growth. Primary and lateral root lengths and a number of lateral root were determined at 3 days after planting (DAP), 7 DAP and 10 DAP. An analy- sis of variance indicated that genotypes, temperature, and days differed significantly in primary and lateral root lengths, number of lateral roots, branching, density, and root weight. Averaged over all temperatures at 10 DAP, primary and lateral root growth was greatest at 30 deg. C, with little growth at 10, 15, or 40 deg. C. Semi-dwarf hybrid 471D had the longest primary and lateral root growth at 30 deg. with 154 cm, as well as the highest number lateral roots. Interspecific genotypes had similar growth patterns to cultivated hybrid 894 at 30 deg. C. Temperature dependent root growth information will be useful in crop modeling of sunflower. INT. SUMMARY: