Can silicon alleviate high light stress in tropical tree seedlings?

Elina Rittelmann1, Bettina Engelbrecht1
1 Functional and Tropical Plant Ecology, University of Bayreuth

P 4.10 in Poster Session

Tropical tree seedlings growing in the forest understory are adapted to very low light conditions. But natural tree fall gaps or forest clearing can result in a sudden and strong increase in light. If the absorbed light energy exceeds the amount required for photosynthesis it can damage the photosystems, resulting in high light stress and decreased plant performance. The nutrient silicon has been shown to reduce high light stress in some agricultural crops. In general, much of the research on silicon is focused on agricultural systems. Since there is little known about the ecological role of silicon in tropical forests, we aim to answer the question of whether silicon can alleviate high light stress in tropical tree seedlings in this study.

In a greenhouse experiment in Panama, seedlings of seven tropical tree species were grown in the shade under low and high soil silicon concentrations. Transfer of the seedlings into full sunlight simulated a treefall gap. High light stress was quantified by chlorophyll fluorescence, a measure for the efficiency of photosystem II, as well as several additional indicators. If silicon alleviates high light stress, it is expected that seedlings grown under high silicon concentrations experience less of a reduction in the measured chlorophyll fluorescence parameter after transfer into full sunlight, then seedlings grown under low silicon concentrations.

Since this is an ongoing study preliminary results will be presented. Preliminary analyses indicates that the effect of silicon on high light stress in tropical tree seedlings varies between species.

Keywords: silicon, high light stress, seedlings, tropics
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