title: Control of Leaf Expansion by Nitrogen Nutrition in Sunflower Plants : ROLE OF HYDRAULIC CONDUCTIVITY AND TURGOR.
abstract: Nitrogen nutrition strongly affected the growth rate of young sunflower (Helianthus annuus L.) leaves. When plants were grown from seed on either of two levels of N availability, a 33% decrease in tissue N of expanding leaves was associated with a 75% overall inhibition of leaf growth. Almost all of the growth inhibition resulted from a depression of the daytime growth rate. Measurements of pressure-induced water flux through roots showed that N deficiency decreased root hydraulic conductivity by about half. Thus, N deficiency lowered the steady-state water potential of expanding leaves during the daytime when transpiration was occurring. As a result, N-deficient leaves were unable to maintain adequate turgor for growth in the daytime. N deficiency also decreased the hydraulic conductivity for water movement into expanding leaf cells in the absence of transpiration, but growth inhibition at night was much less than in the daytime. N nutrition had no detectable effects on plastic extensibility or the threshold turgor for growth.
authors: United States Department of Agriculture, Agricultural Research Service, University of Illinois, Urbana, Illinois 61801.
authors: J W
authors: JW
authors: Radin
authors: J S
authors: JS
authors: Boyer