Effects of Soil Nutrients on Competition and Morphological Plasticity in Impatiens Balsamina L. Population

Abstract

This paper examines the morphological and physiological responses of an annual plant on the wide range of soil nutrient availability, including the photosynthetic activity of plants. Populations of Impatiens balsamina L. are raised over a wide range of densities (20-1,250 plants m–2) at four nutrient levels (1.7-37.7 g-Nm–2) in greenhouse, and three consecutive harvests are performed. The photosynthetic rate of an individual leaf and phenotypic properties of every organ of the plants are determined. The coefficient of intra-specific competitive intensity of the total yield-density equation is found to increase with growth and not vary significantly with nutrient availability. Increased supply of nutrients lead to an increase in Specific Leaf Area (SLA), Stem Weight Fraction (SWF) and light-saturated maximal photosynthetic rate (pmax), whereas Leaf Weight Fraction (LWF) decline with nutrient availability. Nutrient availability does not affect Leaf Area Ratio (LAR), Relative Growth Rate (RGR), Unit Leaf Rate (ULR), or the coefficient of variation of total individual weight. Under low nutrient conditions, plants allocate more dry matter to leaves than to stems, in order to maintain the quality of the leaves and the consequent activity of photosynthesis. Under high nutrient conditions, leaves have high SLA and can maintain high pmax because of high nitrogen concentration in them. Such leaves with high SLA construct a crowded canopy, leading to severe shoot competition. Under such conditions, plants allocate more dry matter to stems, resulting in less crowded canopy architecture with growth. Therefore, the intensity of competition under high nutrient conditions becomes similar to that under low nutrient conditions, with growth.

Keywords: biomass allocation, intra-specific competition, nutrient availability, photosynthesis