Underwater photosynthesis of wheat or rice during submergence

Main area:Eco-physiology
Target group:Biology
Educational level:Bachelor, Masters
Project description:

BACKGROUND - Global climate changes have world-wide caused more heavy rainfall events over the last few decades along with an increased likelihood of devastating floods. Widespread increases in heavy precipitation have occurred, even in places where total rain amounts have decreased because warmer air can hold more moisture. Moreover, shifts in snowfall patterns, the onset of spring and snow melting may all exacerbate some flooding risks. As a consequence, cereals – even those that are currently grown on well-drained soils – may experience flooding throughout the growth season with serious impact on farming practice and eventually also yield.

QUESTION(S) - What is the i) capacity for underwater photosynthesis in barley (Hordeum vulgare) as function of light and CO2 in the flooding environment and ii) importance of leaf gas films for underwater photosynthesis? Barley forms gas films on its super hydrophobic leaf surfaces during inundation and leaf gas films have been shown to improve the flooding tolerance of rice and many wild wetland plants so questions related to gas film functioning are included in the examination of the capacity for underwater photosynthesis.

APPROACH - Leaf segments of 5-6 weeks old barley are incubated in glass vials under controlled light and CO2 conditions and underwater net photosynthesis is measured using the O2 evolution technique. Leaf gas films can be experimentally manipulated using a dilute detergent enabling comparison of photosynthesis rates with and without leaf gas films. Rates of underwater net photosynthesis can be compared to rates obtained in air. Additional tests on effects of waterlogging and submergence can be tested on various commercial genotypes, including the effect of temperature upon mortality during waterlogging and submergence.

Davy, A. J., S. M. Noble, and R. P. Oliver. 1990. Genetic variation and adaptation to flooding in plants. Aquatic Botany 38:91-108.
Pedersen, O., S. M. Rich, and T. D. Colmer. 2009. Surviving floods: leaf gas films improve O2 and CO2 exchange, root aeration, and growth of completely submerged rice. The Plant Journal 58:147-156.
Setter, T. L. and I. Waters. 2003. Review of prospects for germplasm improvement for waterlogging tolerance in wheat, barley and oats. Plant and Soil 253:1-34.
Singh, D. K. and V. Singh. 2003. Seed size and adventitious (nodal) roots as factors influencing the tolerance of wheat to waterlogging. Australian Journal of Agricultural Research 54:969-977.

Methods used:Infra red gas analysis; microelectrodes; micro-respiration chambers; fieldwork; chlorophyll analysis; sugar analysis; manipulation of leaf gas films
Keywords:photosynthesis, respiration, global warming, climate change, flooding tolerance
Project home page: www.flooding.dk
Supervisor(s):  Ole Pedersen