ISSN 1021-4437, Russian Journal of Plant Physiology, 2008, Vol. 55, No. 3, pp. 301–307. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © L.A. Ivanov, D.A. Ronzhina, L.A. Ivanova, 2008, published in Fiziologiya Rastenii, 2008, Vol. 55, No. 3, pp. 332–339.
Global climate changes have stimulated the studies
relating plant characteristics to environmental condi-
tions; such association is fundamental to the under-
standing of species distribution along the climate gradi-
ents [1, 2]. It is especially interesting to follow plant
characteristics along the aridity gradient as the territo-
ries with arid climate occupy 35 to 45% of land area
and progressively expand .
Climate aridization during the Cenozoic era induced
evolutionary structural and functional adaptation of the
photosynthetic organs, such as the development of scle-
rophylly, succulency, and
syndrome [1, 4]. Presently
it is known that the proportion of
species and succu-
lents grows along the aridity gradient, with their great-
est diversity found in the deserts .
The photosynthetic machinery in the plants growing
in extremely arid territories (deserts and semiarid
lands) has been thoroughly investigated [3–5]. Com-
mon features characteristic of the leaf structure in the
xerophytes comprise tissue compactness , reduced
leaf surface , and high values of leaf mass area
(LMA) . In the leaves of plants growing in the
deserts and semiarid lands [6, 7], the content of photo-
synthetic pigments is low. It is also known that the
changes in photosynthetic machinery induced by
drought stress occur at the whole plant content. For
instance, Lambers and Dijekstra  showed that on the
poor and dry soils, the proportion of leaves declined. At
the same time, these characteristics of steppe plants
growing at the beginning of latitudinal gradient of
water deﬁcit are poorly investigated. Gradual strength-
ening of aridity in the latitudinal direction would pro-
mote the adaptation of photosynthetic organs of steppe
xerophytes and the substitution one functional type of
plants for another.
The plants functional types (PFT) are the groups of
species with similar requirements for environmental
conditions and identical response to their changes.
Plants belonging to different PFT have advantages
under different ecological conditions. For instance,
according to the PFT system introduced by Grime ,
the plants pursuing competitor strategy predominate in
the favorable habitats, whereas stress-tolerant plants
have notable advantages under ecological stress.
The aim of this work was to verify the assumption
that the changes in some morphological and functional
indices of leaves as an indicator of the substitution of
the functional types of steppe plants due to climate arid-
ization are not species-speciﬁc.
Changes in Leaf Characteristics as Indicator of the Alteration
of Functional Types of Steppe Plants along the Aridity Gradient
L. A. Ivanov, D. A. Ronzhina, and L. A. Ivanova
Botanic Garden, Ural Division, Russian Academy of Sciences, ul. 8 Marta 202, Yekaterinburg, 620144 Russia;
fax: 7 (343) 210-3859; e-mail: Leonid.Ivanov@botgard.uran.ru
Received May 14, 2007
—Changes in some leaf characteristics: leaf mass area (LMA), content of photosynthetic pigments
and nitrogen in the leaves, leaf mass ratio (LMR) and leaf area ratio (LAR) were investigated in steppe plants
of the Volga land along the gradient of aridity. When drought stress became stronger, the content of chlorophylls
in the leaves, LMR and LAR decreased, whereas LMA and the proportion of carotenoids in the leaves rose. In
the North to South direction, the content of pigments and nitrogen per unit whole plant weight considerably
decreased (4 and 2 times, respectively). The relationship between leaf indices (chlorophyll and nitrogen con-
tents and LMA) differed along this gradient. It was concluded that adaptation of steppe plants to drought stress
generally depended on predominant development of heterotrophic tissues in the leaf and the whole plant. Dur-
ing aridization, the stress-tolerant species became more numerous.
Key words: steppe plants - aridity gradient - adaptation - chlorophyll - nitrogen - leaf mass area - leaf mass ratio -
leaf area ratio - functional types of plants
: LAR—leaf area ratio (ratio of the leaf area to the
whole plant weight); LMA—leaf mass area (leaf mass per unit
area); LMR—leaf mass ratio (ratio of the leaf weight to the whole
plant weight); PTF—plant functional types; SLA—speciﬁc leaf
area (amount of leaf area per unit leaf mass).