Root anatomy of drought sensitive and tolerant maize (Zea mays L.) seedlings under different water potentials

The effect of substrate water potential (ψW) in anatomical characteristics of root seedlings of maize Tuxpeño Sequía C0 (TSC0), drought sensitive, and Tuxpefto Sequía C8 (TSC8), drought resistant, were evaluated. Seventy two hours old seedlings, having an average root length of 5 cm, were maintained for 24 h in vermiculite at ψW of −0.03, −0.65, −1.48 and −2.35 MPa. Anatomical characteristics from both differentiation and cell division root regions were evaluated. Lowest ψW diminished significantly (P=0.0020) transverse root area, number of cells in the cortex parenchyma, thickness of epidermis, exodenmis and cortex, and number of metaxylem vessels in both maize populations. Number of metaxylem vessels and cortex thickness was affected only in TSC0 (15% in both cases); in contrast, the number of cortex cells in the differentiation root region increased 25%, independently of the ψW, and the thickness of the xylem wall from the differentiation root region increased 93% at ψW of −2.35 MPa, in both maize populations. Results suggest that the recurrent selection for drought tolerance induced a significant thinning of the protoderm (78%), endodermis (17%), and xylem vessels (14%) in Tuxpefto maize root and modified the response of root to substrate ψW, including several anatomical changes.