Xylem vessel radii comparison between soybean genotypes differing in tolerance to drought

Authors: NOGUEIRA, MARCO - Embrapa; Livingston, David; Tuong, Tan; SINCLAIR, THOMAS - North Carolina State University

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2020
Publication Date: 2/3/2020
Citation: Nogueira, M., Livingston, D.P., Tuong, T.D., Sinclair, T. 2020. Xylem vessel radii comparison between soybean genotypes differing in tolerance to drought. Journal of Crop Improvement. 34:404-413.

Interpretive Summary: Water conducting vessels in plants, called xylem, can cavitate if they are too large and water levels in the soil are low. Cavitation will cause drought stress on plants and can result in death of the plant or severe reduction of yield depending on when the stress occurs. In this study stems from 2 soybean genotypes that differ in their ability to withstand dry conditions were histologically analyzed and the diameter of their xylem vessels measured. As expected, the more drought tolerant genotype had smaller diameter vessels than the less drought tolerant one. The difference in xylem vessel diameter could be used as a screening tool for breeders to select drought tolerant lines in early generations and improve the overall agronomic characteristics of this important crop.

Technical Abstract: Xylem element radius can be a key factor in determining plant hydraulic conductance and vulnerability to cavitation. Most studies of xylem element radius have been on woody species with a focus on plant survival under severe stress. However, xylem element radius, particularly the largest radius elements, can potentially have an influence on hydraulic flow at more moderate water-deficits. Few studies have offered a detailed distribution of xylem element radii, and even fewer on the distribution in crop species. In this study, the xylem element diameters of two genotypes of soybean (Glycine max L. Merr.) were compared since these two genotypes had been documented to react differently to drying soil. The stems of young plants were harvested from three positions, and in stem cross-sections the number of xylem elements and the radius of each element were determined. While the number of xylem elements did not differ significantly between the two genotypes, the distribution of the radii was skewed to smaller radii in drought-tolerant PI 4719386 as compared to Hutcheson. This difference extended to a difference between the genotypes in the radii of the largest elements, which are considered most vulnerable to cavitation.