Leaf structure and specific leaf mass: the alpine desert plants of the Eastern Pamirs, Tadjikistan

Abstract

This study examines interrelationships between eight leaf attributes (specific leaf mass, area, dry mass, lamina thickness, mesophyll cell number per cm#, mesophyll cell volume, chloroplast volume, and number of chloroplasts per mesophyll cell) in field-grown plants of 94 species from the Eastern Pamir Mountains, at elevations between 3800 and 4750 m. Unlike most other mountain areas, the Eastern Pamirs, Karakorum system, Tadjikistan provide localities where low temperatures and radiation combine with moisture stress at high altitudes. For all the attributes measured, significant differences were found between plants with different mesophyll types. Leaves with dorsiventral palisade structure (dorsal palisade, ventral spongy mesophyll cells) had thicker leaves with larger but fewer mesophyll cells, containing more and larger chloroplasts. These differences in mesophyll type are reflected in differences in the total surface of mesophyll cells per unit leaf area (A mes \A) or volume (A mes \V ). Plants with isopalisade leaf structure (palisade cells under both dorsal and ventral surfaces) are more commonly xerophytes and their increased values of A mes \A and A mes \V decrease CO # mesophyll resistance, which is an important adaptation to drought. Path analysis shows the critical importance of mesophyll cell volume in leading to the covariance between the different leaf attributes and hence to specific leaf mass (SLM), even though mesophyll cell volume is not itself strongly correlated with SLM. This is because mesophyll cell volume increases SLM through its effects on leaf thickness and chloroplast number per cell, but decreases SLM through its negative effect on mesophyll cell density.

Leaf structure and chemical composition as affected by elevated CO2: genotypic responses of two perennial grasses

“…Because CO # stimulates growth, and both SLA and [N m ] lf change with plant size, the decrease in [N m ] lf observed when plants grown in ambient and elevated CO # are compared at a given age could be the result of plants grown at elevated CO # being larger (Coleman et al, 1993). In addition, [N m ] lf is often negatively correlated to SLA (Reich & Walters, 1994 ;Garnier et al, 1997 ;Pyankov et al, 1999) ; thus a further question is whether the decrease in C. Roumet et al [N m ] lf is linked to the decrease in SLA, as predicted by the model of Luo et al (1994).…”

Comparative analyses of leaf anatomy of dicotyledonous species in Tibetan and Inner Mongolian grasslands

“…Species in different genera or families have different sensitivities to various ecological factors; this may result in leaf characteristics having no significant relationship with climatic factors [19,20]. However, on the whole, in our sampling plots in the Tibetan alpine grasslands and Inner Mongolian temperate grasslands, the PCA 1 of whole species had weak negative correlations with growing season temperature and no significant relationship with precipitation; indicating that the effects of temperature were more notable than those of precipitation across the study area.…”

“…Large-scale studies generally contain various species, the genotypes of these species differ, their sensitivities to ecological factors may also vary, and plants with different taxonomies or from different functional groups may have different responses to environmental change; leading to the differences overwhelming the intrinsic relationships between leaf anatomy and environment [19,20]. It is therefore necessary to compare the responses of plants with different taxonomies and life forms.…”

A comparative analysis of photosynthetic characteristics of hulless barley at two altitudes on the Tibetan Plateau

“…The primary reason for the greater photosynthetic capacity of plants at higher altitude is that the reduction in RuBP carboxylation is less than the reduction in RuBP oxygenation with increasing altitudes, which causes much less of a reduction in photosynthesis compared to that observed during photorespiration in alpine plants in the alpine environment of the Tibetan Plateau (Terashima et al 1995). In addition, photosynthetic proteins (Körner et al 1989, Morecroft and Woodward 1996, Pyankov et al 1999, stomatal density (Körner et al 1986), rate of gas diffusion (Gale 1972) and the activities of photosynthetic enzymes (Castrillo 2006) in the leaves of alpine plants have been shown to increase with increasing altitudes (Körner et al 1989), all of which correlate with photosynthetic acclimation to the climatic conditions of low air pressure, cool temperature (Körner 2007), and high irradiation (Oguchi et al 2003). Indeed, those positive effects could overcome the negative effect of decreasing CO 2 partial pressure with increasing altitudes in an alpine environment.…”