Effects of different water regimes on the anatomical characteristics of roots of grasses promising for revegetation of areas surrounding hydroelectric reservoir

Silvana Da Silva,Ângela Maria Soares,Evaristo Mauro De Castro

doi:10.1590/s1413-70542003000200020

Abstract

The objective of this study was to evaluate the effect of different water regimes on some aspects of root anatomy of three grasses: Echinochloa pyramidalis (canarana), Setaria anceps (setária) and Paspalum paniculatum (paspalo). The plants were cultivated in a greenhouse and submitted to three water regimes: daily watering; suspension of watering and suspension of watering followed by submersion of the root system. Segments of the middle part of the roots were taken and submitted to classical techniques in botany for slide making and tissue analysis. Anatomical differences were observed among the three grasses submitted to water regimes regarding the number of cell layers in the external cortex and thickening of lignin and suberin. The submerged roots of the three species presented an increasing tendency in the proportion of the area of the cortex destined for the aerenchyma besides thickening of the endodermis and the cells of the medullar parenchyma. The aerenchyma presence in the three water regimes suggested it is a characteristic of these species. The adaptations developed by these species contributed to the understanding of their occurrence in areas that are subject to drought periods and successive floods.

Highlights

Areas surrounding hydroelectric reservoirs are subject to damage caused by the removal of the superficial soil layer and to the effects of periodic flooding that are followed, paradoxically, by characteristic periods of water restriction in the soil.Plant tissue responses to water stress depend on the physiological properties of the cell components and the anatomic characteristics that regulate the transmission of the water stress effect to the cells
In canerana (Figure 1 a,b,c) the external cortex with three layers of heterodiameteric cells covered by a fairly thick cell wall of lignin and/or suberin in the nonirrigated treatment was observed below the unistratified epiderm (a); one layer below the epiderm without thickening and two layers with thickening of lignin and/or suberin in the irrigated treatment (b). a layer below the epiderm without thickening was observed in the root system submersion treatment (c) and only one cell layer with lignin and/or suberin thickening
In Setária (Figure 1. d, e, f) a unistratified epiderm and the external cortex with two layers of heterodiameteric cells were observed in the non-irrigated treatment (d); two to three layers of heterodiametric cells were observed in the irrigated treatment (e) and one to two layer of heterodiametric cells in the treatment with submerged root system (f)

Summary

Introduction

Plant tissue responses to water stress depend on the physiological properties of the cell components and the anatomic characteristics that regulate the transmission of the water stress effect to the cells. The difference in the response to water stress among mature regions and regions of tissue growth seems to be due to anatomic differences (Matsuda & Rayan, 1990). Anatomical alterations may occur in plants under water deficit to protect and adapt the species to this stress. These alterations are probably due to lignin or suberin deposits found in the exodermis, endoderm and cell layers neighboring the root cortex and medulla (Baruch & Mérida, 1995) that protect against desiccation and cortex cell death (Sharp & Davies, 1985). Cell elongation is expected to be more sensitive than cell division (Levitt, 1980)

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