Skip Navigation

This Article
Right arrow Full Text (PDF)
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Gutschick, V. P.
Right arrow Articles by Kay, L. E.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Gutschick, V. P.
Right arrow Articles by Kay, L. E.
Agricola
Right arrow Articles by Gutschick, V. P.
Right arrow Articles by Kay, L. E.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 1995 Oxford University Press

RESEARCH-ARTICLE

Nutrient-limited growth rates: quantitative benefits of stress responses and some aspects of regulation

V. P. Gutschick1 and L. E. Kay

Department of Biology, New Mexico State University Las Cruces, NM 88003, USA

1To whom correspondence should be addressed. Fax: +1 505 646 5665.

Young sunflower plants (Helianthus annuus L.) under stress of low nitrate or phosphate availability exhibited increases in root: shoot ratio and in kinetic parameters for uptake. They showed no significant changes in photosynthetic utilization of either nutrient. Increases in root: shoot ratio were achieved by early and persistent suppression of shoot growth, but not root growth. Affinity for phosphate uptake, 1/Km(P), increased with phosphate stress, as did affinity for nitrate uptake, 1/Km(N), with nitrate stress. Maximal uptake rate, Vmax, for phosphate uptake increased with phosphorus stress; Vmax for nitrate did not increase with nitrogen stress. Phosphate Vmax was related strongly to root nutrient status. Decreases in Vmax with plant age were not well explained by changes in age structure of roots. Estimated benefits of acclimatory changes in root: shoot ratio and uptake kinetics ranged up to 2-fold increases in relative growth rate, RGR. The relation of RGR to uptake physiology followed predictions of functional balance moderately well, with some systematic deviations. Analyses of RGR using growth models imply no significant growth benefit from regulating Vmax, specifically, not from down-regulating it at high nutrient availability. Quantitative benefits of increases in root: shoot ratio and uptake parameters are predicted to be quite small under common conditions wherein nutrient concentrations are significantly depleted by uptake. The root: shoot response is estimated to confer the smallest benefit under non-depleting conditions and the largest benefit under depleting conditions. Even then, the absolute benefit is predicted to be small, possibly excepting the case of heterogeneous soils. Depleting and non-depleting conditions are addressed with very different experimental techniques. We note that a theoretical framework is lacking that spans both these cases, other than purely numerical formulations that are not readily interpreted.

Key words: Nutrient stress, nutrient uptake, nutrient use efficiency, relative growth rate, Helianthus annuus


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.