Small, stiffened cells allow them to penetrate better: A previously unknown feature of roots enables cereal plants to develop harder soils, researchers report. The studies show that plants with this predisposition can better draw water and nutrients from compacted soils. Crops grown for this trait could thus increase yields in regions of the world that are increasingly affected by soil compaction, say the scientists.
The soils of the world form the basis of life on land: They enable plant growth and thus the production of terrestrial biomass as well as food for animals and humans. Various factors shape the fertility of soils – mechanical resistance is a particularly important one. If the soil is hard and compacted, there are few pores that allow water to be absorbed and stored and roots offer growth opportunities. “Compacted soil limits the productivity of plants because it limits the exploration of deeper layers of the soil, which in turn limits access to nutrients and water,” explains Hannah Schneider of Pennsylvania State University in University Park. There are, however, plant species and varieties whose roots can penetrate hard soils comparatively well and use them more deeply. In the end, they are more efficient in drought or low soil fertility.
A new feature is emerging
The foundations on which these skills are based, however, are still not fully understood. Schneider and her colleagues dedicate themselves to this research topic. Her current study focused on examining the physiological characteristics of the roots in different genotypes of maize and wheat in relation to their respective ability to root through hard soils. In experiments in greenhouses and in the field, the plants were cultivated with different soil compaction. Then their penetration ability and the associated biomass formation were recorded. Using modern analysis methods, the researchers then gained insights into the fine structures of the roots and their mechanical strength.
The team was able to show that plants with particularly powerful roots develop a trait that the scientists call Multiseriates Morticales Sclerenchyma (MCS). It is a strengthening tissue directly under the surface of the roots, which is characterized by particularly small cells with thick walls. Corresponding roots also have a higher concentration of lignin, the researchers report. This is a complex organic polymer that is important in the formation of cell walls, especially in wood and bark tissue, and which makes them stable.
More lignin also gives the MCS roots a higher tensile strength and allows them a greater bending force in the area of the root tip compared to non-MCS genotypes, the studies showed. This is particularly beneficial when penetrating hard soil layers, the researchers explain. In the maize genotypes with MCS, the root systems reached 22 percent deeper into the compacted soils than in the lines without the trait. The associated optimization of the use of nutrients and water was also reflected in the growth above ground: the plants developed a 39 percent higher shoot biomass, according to the evaluations.
Potential for plant breeding
“We have already detected MCS in lines of maize, wheat, barley and other cereals. This suggests that MCS could occur analogously in different species and is thus an important characteristic for stress tolerance and higher yields in cereal crops, ”says Schneider. The researchers have also already discovered clues about the genetic basis of the trait. This shows that a targeted selection for the trait is possible within the framework of breeding programs.
Maize plants in particular, which can take root deeper in hard soils, have the potential to improve the nutritional situation in problematic regions, say the scientists. This is especially true in view of the changing climate, which makes large areas of the world more prone to drought. “The discovery bodes well for global agriculture as the trait increases drought tolerance, nitrogen efficiency and thus carbon sequestration,” says co-author Jonathan Lynch of the University of Nottingham in Leicestershire. “Breeding for this characteristic could therefore also be helpful in the development of new crops for climate protection,” says the researcher.
Source: Pennsylvania State University, Article: PNAS, doi: 10.1073 / pnas.2012087118