Strong plastic responses in aerenchyma formation in F1 hybrids of Imperata cylindrica under different soil moisture conditions

There is insufficient evidence demonstrating how phenotypic plasticity in specific traits mediates hybrid performance. Two ecotypes of Imperata cylindrica produce F1 hybrids. The early flowering type (E-type) in wet habitats has larger internal gas spaces (aerenchyma) than the common type (C-type) in dry habitats. This study evaluated the relationships between the habitat utilisation, aerenchyma plasticity, and growth of I. cylindrica accessions. We hypothesize that plasticity in expressing parental traits explains hybrid establishment in habitats with various soil moisture conditions.

Aerenchyma formation was examined in the leaf midribs, rhizomes, and roots of two parental ecotypes and their F1 hybrids in their natural habitats. In common garden experiments, we examined plastic aerenchyma formation in the leaf midribs, rhizomes and roots of natural and artificial F1 hybrids and parental ecotypes. Their vegetative growth performance was also quantified.

In the natural habitats where soil moisture content varied widely, the F1 hybrids showed larger variation of aerenchyma formation in the rhizomes than their parental ecotypes. In the common garden experiments, the F1 hybrids showed high plasticity of aerenchyma formation in the rhizomes, and their growth was similar to that of C-type and E-type under drained and flooded conditions, respectively.

The results demonstrate that the F1 hybrids of I. cylindrica exhibit plasticity in aerenchyma development in response to varying local soil moisture content. This characteristic allows the hybrids to thrive in diverse soil moisture conditions.