Plant and Soil

, Volume 311, Issue 1, pp 73–86

Effects of silicon nutrition on cadmium uptake, growth and photosynthesis of rice plants exposed to low-level cadmium

Regular Article

DOI: 10.1007/s11104-008-9659-4

Cite this article as:
Nwugo, C.C. & Huerta, A.J. Plant Soil (2008) 311: 73. doi:10.1007/s11104-008-9659-4

Abstract

The effect of silicon (Si) nutrition on low-level cadmium (Cd) toxicity symptoms was investigated in hydroponically-grown rice seedlings (Oryza sativa L.). Silicon (0.0, 0.2, or 0.6 mM) was added when seedlings were 6 or 20 days old representing early (SiE) or late (SiL) Si treatment, respectively. Cadmium (0.0 or 2.5 μM) was added when seedlings were 6 days old. Measurements included generation of CO2 and light response curves; chlorophyll fluorescence analysis; growth; and tissue-element content analysis. Our results showed that low-level Cd treatment generally inhibited growth and photosynthesis. However, the addition of 0.2 or 0.6 mM SiE or SiL significantly reduced root- and leaf-Cd content. Consequently, the addition of 0.6 mM SiL significantly alleviated low-level Cd-induced inhibition of growth. Furthermore, 0.2 mM Si treatment significantly reduced gs compared to 0.0 or 0.6 mM Si without inhibiting A, especially in +Cd plants, suggesting an increase in instantaneous water-use-efficiency (IWUE). Additionally, in +Cd plants, the addition of 0.6 mM SiE significantly reduced Fo but increased Fv/Fm, while treatment with 0.2 mM SiL significantly increased qP, suggesting an increase in light-use-efficiency. We thus, propose that 0.6 mM SiL treatment is required for the alleviation of low-level Cd-mediated growth inhibition. Furthermore, we suggest that 0.2 mM Si concentration might be close to the optimum requirement for maximum Si-induced increase in IWUE in rice plants, especially when under low-level Cd-stress. Our results also suggest that Si alleviates low-level Cd toxicity by improving light-use-efficiency.

Keywords

Chlorophyll fluorescenceInstantaneous water-use-efficiencyLow-level cadmiumSiliconStomatal conductance

Abbreviations

A

net CO2 assimilation rate

Amax

maximum net CO2 assimilation rate

Ca

ambient CO2 concentration

CE

carboxylation efficiency

Ci

intercellular CO2 concentration

E

transpiration rate

Fm

maximum chlorophyll fluorescence yield in a dark-adapted state

Fo

minimum chlorophyll fluorescence yield in a dark-adapted state

Fo/Fm

basal quantum yield of non-photochemical processes in PS2 in a dark-adapted state

Fv

maximum variable fluorescence yield in a dark-adapted state

Fv/Fm

quantum efficiency of open PS2 centers in a dark-adapted state

gs

stomatal conductance rate

gsmax

maximum stomatal conductance rate

Is

photosynthetic light-saturation point

IWUE

instantaneous water-use-efficiency

PS

photosystem

qN

non-photochemical quenching coefficient in a light-adapted state

qP

photochemical quenching coefficient in a light-adapted state

RUBISCO

ribulose-1, 5-bisphosphate carboxylase/oxygenase

SiE

Si was added (early) when plants were 6 days old

SiL

Si was added (late) when plants were 20 days old

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Department of BotanyMiami UniversityOxfordUSA