Effect of drought on leaf development and dry matter production of the cassava (Manihot esculenta Crantz.) plant.

Cassava (Manihot esculenta Crantz) was grown in the field to study the effect of water deficit caused by drought on leaf and plant development, storage root growth and yield. Soil water content in the first 50 cm was monitored weekly. Leaf number per plant, leaf area index (LAI), leaf lobe length, plant and storage root dry matter accumulation were measured every two weeks. Leaf emergence, stem elongation and leaf senescence were also investigated. Water stress during drought was found to reduce leaf emergence rate (LER) and the size of the leaves emerged and expanded during the drought period. It also increased leaf senescence at the base of the canopy when LAI was > 3, leading eventually to a decreased LAI. The reduction in LAI was associated with a lower dry matter production. Storage root production was less sensitive to water stress than shoot growth since the proportion of assimilate translocated in the storage roots increased.