Full Length Research Paper

Dry matter partitioning and physiological responses of Coffea arabica varieties to soil moisture deficit stress at the seedling stage in Southwest Ethiopia

M. Worku¹ and T. Astatkie^2*

¹Department of Horticulture and Plant Sciences, College of Agriculture and Veterinary Medicine, Jimma University, P. O. Box 307, Jimma, Ethiopia.

²Department of Engineering, Nova Scotia Agricultural College, Truro, Nova Scotia, B2N 5E3, Canada.

*Corresponding author. E-mail: tastatkie@nsac.ca . Tel: 1 902 893 6694.

Fax: 1 902 893 1406.

Accepted 2 July, 2010

 Abstract

Dry matter partitioning, leaf chemical contents and morpho-physiological responses of six Coffea arabica varieties were tested in 15 and 30 days water stress followed by 15 days re-watering at seedling stage in Jimma, southwest Ethiopia. Repeated measures analysis revealed that differences among varieties depended on water stress and recovery periods for leaf P content and shoot mass ratio (SMR). Regardless of stress and recovery periods, significant differences among varieties were found for root fresh weight (RFW), leaf dry weight (LDW), leaf mass ratio (LMR), root mass ratio (RMR) and root to shoot ratio (RSR). Varieties 7440, 7487, 74140 and 74148 showed relatively high biomass allocation to roots whereas variety 741 allocated more to shoots. Variety 7487 had higher RFW and LDW. Significant differences among stress and recovery periods were also obtained; leaf K, Ca and Mg contents and SMR significantly increased whereas leaf P content, LMR, RMR and RSR decreased during stress. Higher leaf and root biomass fraction, and fresh weights were obtained after 15-day stress and recovery, respectively but similar root biomass fraction after 30-day stress and 15-day recovery and fresh weights during stress. Significantly higher leaf folding, stomatal resistance, leaf temperature and wilted seedlings and the lowest relative water content were observed after 30-day water deficit. Overall, variable coffee plant responses to drought stress periods, and faster recovery of the seedlings after re-watering were observed.

Key words: Leaf chemical contents, morphological responses, repeated measures, water deficit stress.