title: [The analysis of the causes of variability of the relationship between leaf dry mass and area in plants].
abstract: The lamina dry mass: area ratio (LMA - Leaf Mass per Area) is a quite variable trait. Leaf dry mass consists of symplast mass (a set of all leaf protoplasts) and apoplast mass (a set of all cell walls in a leaf). The ratio between symplast and apoplast masses is positively related to any functional trait of leaf calculated per unit of dry mass. The value of this ratio is defined by cells size and their number per unit of leaf area, number of mesophyll cells layers and their differentiation between palisade and spongy ones, and also by density of cells packing. The LMA value is defined by leaf thickness and density. The extent and direction of variability in both leaf traits define the extent and direction of variability in LMA. Negative correlation between leaf thickness and density reduces the level of LMA variability. As a consequence of this correlation the following pattern emerges: the thinner a leaf, the denser it is. Changes in the traits that define the LMA value take place both within a species under the influence of environmental factors and between species that differ in leaf structure and functions. Light is the most powerful environmental factor that influences the LMA, increase in illumination leading to increase in LMA. This effect occurs during leaf growth at the expense of structural changes associated with the reduction of symplast/apoplast mass ratio. Under conditions of intense illumination, LMA may increase due to accumulation of starch. With regard to the majority of leaf functions, the mass of starch may be ascribed to apoplast. Starch accumulation in leaves is observed also under conditions of elevated CO2 concentration in the air. Under high illumination, however, LMA increases also due to increased apoplast contribution to leaf dry mass. Scarce mineral nutrition leads to LMA increase due to lowering of growth zones demands for phothosyntates and, therefore, to increase in starch content of leaves. High level of mineral nutrition during leaf growth period leads to LMA increase at the expense of mesophyll thickening where components of photosynthesis system are located. When additional environmental factors are involved, starch accumulation may be partly responsible for increase in LMA. LMA increase at the expense of starch accumulation, unlike that at the expense of mesophyll thickening, is accompanied by increased leaf density. Under conditions of water deficiency LMA increases, which in mature leaf may be caused by starch accumulation. LMA increase during leaf growth period under conditions of water deficiency is associated with decrease in the symplast/apoplast mass ratio.
authors.forename: S P
authors.initials: SP
authors.lastname: Vasfilov
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D003681:Dehydration; D008027:Light; D008903:Minerals / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D063245:Plant Development; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000502:physiology / Q000528:radiation effects; D018521:Plant Physiological Phenomena; D010944:Plants / Q000033:anatomy & histology* / Q000528:radiation effects; D013213:Starch / Q000096:biosynthesis; D014867:Water / Q000378:metabolism
chemical_list: D008903:Minerals; D014867:Water; D002245:Carbon Dioxide; D013213:Starch