Root versus shoot biomass: Responses to water, nitrogen, and phosphorus applications for Agave lechuguilla
- Univ. of California, Los Angeles (USA)
- Centro de Investigacion en Quimica Aplicada, Coahuila (Mexico)
Shoot and root growth of Agave lechuguilla, a Crassulacean acid metabolism (CAM) succulent widespread in the Chihuahuan Desert, was examined under natural conditions and with two watering regimes, five treatments involving N application to the soil surface, and three treatments involving P application. Under natural conditions root of A. lechuguilla made up only 3.7% of the total plant dry weight, suggesting that this species may be especially sensitive to changes in soil resources. Over the 2-yr study period, increasing the availability of soil water by weekly irrigation increased shoot dry weight of A. lechuguilla by 40% and root dry weight by 75%, which represented a doubling of the increment in plant growth compared with control plants receiving only rainfall. This doubling is consistent with changes in the Water Index (a relative measure of net CO{sub 2} uptake that has a maximum value of unity under wet conditions), which was predicted to be twice as large for the irrigated condition. The greater enhancement of root compared with shoot growth caused by increased water availability should lead to slightly more water uptake, which can compensate for the slightly greater reliance on daytime CO{sub 2} uptake by A. lechuguilla under wet conditions. The leaf N level tended to rise with the application level of N, the increase being 15% at 500 kg N ha{sup {minus}1}, whereas the leaf P level was little affected by P applications up to 500 kg ha{sup {minus}1}. Application of 100 kg N ha{sup {minus}1} increased shoot dry weight by 51% over the 2-yr study period with no effect on root dry weight, and application of 500 kg P ha{sup {minus}1} increased shoot dry weight by 40% but decreased root dry weight by 37%. At these application levels, which were optimal for shoot growth, the roots of A. lechuguilla made up only about 2% of the total plant dry weight.
- DOE Contract Number:
- FC03-87ER60615
- OSTI ID:
- 6617232
- Journal Information:
- Botanical Gazette (Chicago); (USA), Vol. 150:4; ISSN 0006-8071
- Country of Publication:
- United States
- Language:
- English
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