AOBPreview published online on October 24, 2007
Annals of Botany, doi:10.1093/aob/mcm236
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Morphological and Physiological Responses to Sediment Type and Light Availability in Roots of the Submerged Plant Myriophyllum spicatum
1 Institute of Subtropical Agriculture, the Chinese Academy of Sciences, Changsha 410125, China
2 College of Bioscience and Biotechnology, Hunan Agriculture University, Changsha 410128, China
3 Graduate School of the Chinese Academy of Sciences, Beijing 100039, China
* For correspondence. E-mail: yonghongxie{at}163.com
Received: 22 March 2007 Returned for revision: 7 June 2007 Accepted: 31 July 2007
Background and Aims: Both sediment and light are essential factors regulating the growth of submerged macrophytes, but the role of these two factors in regulating root morphology and physiology is far from clear. The responses of root morphology and physiology to sediment type and light availability in the submerged plant Myriophyllum spicatum were studied and the hypothesis was tested that a trade-off exists in root growth strategy between internal aeration and nutrient acquisition.
Methods: Plants were grown on two types of sediment (fertile mud and an infertile mixture of mud and sandy loam) and under three levels of light availability (600, 80 and 20 µ mol m–2 s–1) in a greenhouse.
Key Results: The significantly higher alcohol dehydrogenase (ADH) activity in root tissues indicated that oxygen deficiency existed in the plants growing in fertile mud and low (or high) light environments. Significantly, low plant N and P concentrations indicated that nutrient deficiency existed in the mixed sediment and high light environment. As a response to anoxia, plants did not change the porosity of the main roots. The effect of sediment type on root morphology was insignificant under higher light environments, whereas root diameter generally decreased but specific root length (SRL) increased with decreasing light availability. Both low light and fertile mud jointly led to lack of second-order laterals. More biomass was allocated to lateral roots in infertile environments, whereas mass fractions of laterals were lower in low light and mud environments.
Conclusions: These data indicate that this plant can achieve the trade-off between internal aeration and nutrient acquisition by adjusting the structure of the root system and the pattern of biomass allocation to different root orders rather than root morphology and root porosity.
Key words: Adaptation, aeration, anoxia, biomass allocation, nutrient, morphological plasticity, oxygen, root system, submerged macrophytes, Myriophyllum spicatum