C - Lublin

SURFACE AREA OF PLANT ROOTS FROM WATER VAPOR AND
NITROGEN ADSORPTION AS AFFECTED BY pH AND ALUMINUM
INTRODUCTION
Szatanik- Kloc A.
Surface area of plant root system is a key parameter for description of
absorption of water and nutrients by plants (Nye 1973, Silberbrush and Barber
1983). Usually the surface area of plant root of a few square centimeters per gram,
measured by immersion of the roots in water or in electrolyte solutions, is reported
(Carley and Watson 1966, Ansari et al. 1995). In these methods a very thick layer
of water (solution) adhered to the surface and shading real surface details is taken
as a measure of the surface area. Certainly the finest roots do not contribute to this
value and the external geometrical surface of root is measured. Very high root
surface areas result from direct calculation of the geometric field of root + root hair
(from length and diameter). In this way Dittmer estimated the surface area of one
rye plant roots of 765 square meters (Vilee 1978). Close to the latter value, the
specific surface area of roots can be estimated from water vapor adsorption
isotherm. Low-temperature nitrogen adsorption, although widely used in surface
area determination of great number of adsorbents has not yet been used for plant
root material.
The purpose of the present studies was to compare surface areas of plant roots
using both adsorbates and to estimate changes of these surface areas under low pH
and aluminum stress of different concentrations. This is known that aluminum ions
severely alter plant roots cell structures.
MATERIALS AND METHODS
Tillering and shooting stage plant roots of two wheat (Triticum L.) varieties:
acid resistant (Inia 66/16) and acid sensitive (Henika), and a very sensitive barley
(Ars) were studied. The plants were grown in a nutrient solution prepared
according to Marshner and Romheld (1983), at pH=7 with 16 h (23oC) / 8 h
(18oC) day/night regime. After the plants reached the requested growth stage, the
pH was adjusted to the value of 4.0 and aluminum chloride was added to reach an
Al level of 20 mg dm 3 that induced a strong toxicity. After one week, all roots were
harvested, rinsed 3 times in 0.01 mol dm-3 HCl, 5 times in distilled water, air dried
and collected for further analyses.
Water vapor adsorption isotherms were measured using a vacuum chamber
method (Polish Standard PN-Z19010-1) at 298±0.1 K. (Jozefaciuk and Szatanik-
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