Alhassan Lansah Abdulai, Folkard Asch, Nick van de Giesen:
Physiological and Morphological Responses of Sorghum Bicolor to Static and Dynamic Drought Conditions


1University of Bonn, Agricultural Sciences and Resource Management for the Tropics and Sub-tropics, Germany
2University of Bonn, Plant Nutrition in the Tropics and Subtropics, Germany
3University of Bonn, Ecology and Natural Resources Management, Germany

Drought is a major abiotic stress that severely affects agricultural systems and food production. It is generally accepted to be the widest spread abiotic stress experienced by crop plants and the major limiting factor to crop production in most areas of the world, especially in the tropics. Intermittent drought at critical stages of cereal crops reduces yield.

Sorghum, grown extensively in the dry parts of the tropics, is reputedly one of the most drought tolerant crops. Yields are still limited by drought because most of the mechanisms of drought tolerance, their interactive effects, and associated morphological and physiological modifications and symptoms have not been fully identified and/or understood by plant breeders and plant physiologists.

An experiment has been set up in a green house to investigate the morphological and physiological responses of a sorghum genotype grown in two different soil types and subjected to permanently sub-optimal water availability in contrast to a drying cycle with subsequent re-watering.

A sorghum variety (ICSV 111 IN), was planted in pots constructed from PVC pipes with internal diameter of 0.15m and 0.5m height. Each pot was subdivided into 4 sections of 0.125m height held together by cellotape to facilitate the easy assessment of moisture and root distribution within the pots. Two soils (sandy loam and loamy sand), differing in matric potentials, and three different water treatments (field capacity (control), constant drought, and dynamic drought) were used for the study.

Biomass partitioning, root biomass development in four soil depths, root water potential, chemical composition of the xylem sap, transpiration and photosynthesis will be studied in relation to available soil water content, matric potential of the soil and soil type. The results are expected to elucidate whether the plant responds to the total amount of water available or to the pressure gradient between xylem and soil. Implications for modelling and genotype development will be discussed.

Keywords: Biomass partitioning, drought, root-shoot-communication, soil properties, sorghum


Contact Address: Folkard Asch, University of Bonn, Plant Nutrition in the Tropics and SubtropicsKarlrobert Kreiten Straße 13, 53115 Bonn, Germany, e-mail:
Andreas Deininger, September 2004