|Seiler Gerald J,|
Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 12, 1994
Publication Date: N/A
Interpretive Summary: Roots provide the lifeline between the plant and the soil. They provide a system to transport water and nutrient for survival. The number of roots, rooting patterns and rooting depth are important characteristics needed for sunflower survival. The problem is that we do not know what variability in rooting characteristics is available from the wild species. Several of the wild species have been adapted for survival under limited water conditions. Six wild interspecific sunflower genotypes and two hybrids were evaluated for primary and lateral root length, number of lateral roots, mean lateral root length and hypocotyl length. Considerable variability for rooting characteristics was observed in the interspecific genotypes. Variability for specific characters is necessary to make any progress in a breeding and selection program to improve cultivated sunflower. The next step will be to evaluate the interspecific genotypes under field conditions to correlate the responses in the laboratory and under field conditions.
Technical Abstract: Roots play a major role in maintaining a water supply to plants. Differences in root density and rooting depth exists in many crops. Primary and lateral root growth of 10-day old seedlings of eight sunflower (Helianthus ssp.) genotypes were evaluated to determine the chronological root growth, genetic differences, and vascular bundle pattern. Seeds were germinated and seedlings grown in polyethylene pouches at 25 deg. C in the dark for 10 days. Primary root length, lateral root length, and number of lateral roots were determined for seven consecutive days after planting (DAP), beginning at day two for the primary root. An analysis of variance indicated that genotypes differed significantly in primary and lateral root length, total root length, number of lateral roots, mean lateral root length, but not branching intensity. Ten DAP, genotype PET had the longest primary roots (9.0 cm), and genotype 471D had the longest lateral roots (20.5 cm). Genotype PET had the greatest number of lateral roots with 14.3 root/seedling. The greatest increases in primary and lateral root lengths occurred during the fourth through the sixth DAP. The tetrarch (four) vascular bundle arrangement was the only pattern observed in the genotypes examined. A high positive correlation was observed between primary and lateral root lengths, number of lateral roots, with the lowest correlation between primary root length and branching intensity. There appears to be sufficient variability for selection to genetically alter root growth patterns in sunflower, but further studies are needed to correlate laboratory observations with rooting responses under field conditions.