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Drought‐Induced Nitrogen Retranslocation in Perennial C4 Grasses of Tallgrass Prairie
Author(s) -
Heckathorn Scott A.,
DeLucia Evan H.
Publication year - 1994
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941592
Subject(s) - deserts and xeric shrublands , shoot , perennial plant , rhizome , biology , agronomy , botany , interspecific competition , drought tolerance , phenology , ecology , habitat
We determined if drought—induced nitrogen retranslocation occurs in perrenial grasses of tallgrass prairie, as suggested from studies of annual changes in plant N content. To test this, we analyzed six C 4 grasses representing a wide range of drought tolerance for shoot, rhizome, and root N before and after controlled drought. Shoot N concentration decreased in all species during drought (31—41%), including in recently expanded leaves (23—38%). No consistent pattern with respect to drought tolerance was apparent in these decreases or in observed changes in distribution of whole—plant N, although there was some suggestion of a mesic—to—xeric gradient in the magnitude of retranslocation. For example, the proportion of total plant N allocated to shoots decreased during drought 20—29% in the most mesic species over three experiments, 2—12% in the three intermediate species, and 4—6% in the two most xeric species, for pre— vs. post—drought comparisons. However, when drought—stressed plants were compared to well—watered age controls, the respective values were 20—21%, 12—20%, and 0.19%, the apparent result of size—related changes in N allocation in control plants in one experiment. In most cases, shoot N was moved primarily into rhizomes, though in one species with intermediate drought tolerance, evidence suggested that much of the retranslocated shoot N was apparently lost through fine—root turnover. Retranslocation of shoot N to rhizomes and roots, confirmed by monitoring movement of 3 5 S—methionine, was in response to drought stress rather than phenology and involved the entire shoot (e.g., blades, culms, recently expanded leaves). Post—drought photosynthesis and leaf N concentration remained well below predrought levels 6 d following rewatering. Thus decreases in leaf N status during drought as a consequence of retranslocation likely result in lower photosynthetic capacity and decreased whole—plant carbon gain following relief of water stress after rain. Drought—induced retranslocation may serve to protect plant N from loss of herbivory, fire, and volatilization during periods when soil N uptake and carbon assimilation are limited by water availability.