Morphology, biochemistry, and yield of cassava as functions of growth stage and water regime

Abstract

Water deficit affects morphological attributes and physiological and biochemical processes important to plants. Although cassava crop is known for its rusticity and adaptability to adverse environmental conditions, there have not been any studies reporting the effects of water deficit at different growth stages on cassava morphology and biochemistry. The objective of this research was to evaluate the morphological, anatomical, biochemical, and yield responses of cassava under different water regimes in three growth stages. The experimental design used was completely randomized 3 × 3 factorial scheme consisting of three growth stages (GS) [90–180 (GS3), 180–270 (GS4), and 270–360 days after planting (DAP) (GS5)] and three soil water tensions (-10, -40, and -70 kPa) with five replicates. Plants were affected, mainly in GS3, by -40 and -70 kPa soil tensions, with decreases in stem diameter, plant height and number of leaves. Leaf anatomy was also affected by water deficit in GS3, with reductions in the mesophyll thickness (13.7%), spongy parenchyma (19.9%), epidermal cells on the blade abaxial surface (18.0%) and in the number of xylem vessels (15.8%); in addition, there was an increase in the wall thickness (105.0%) and in the diameter (85.5%) of the xylem vessels. Under prolonged water deficit, there was an increase in the activity of superoxide dismutase and catalase, which were efficient in controlling H2O2. The imposition of water deficit drastically reduced the yield of commercial and tuberous roots in GS3 (82.1% and 65.0%) and GS5 (45.7% and 32.5%). Our study shows that the period of crop susceptibility to water deficit is longer than previously thought, evidencing the need for greater attention to water availability between 90 and 180 and between 270 and 360 DAP, as it may aid in reducing the negative effects of water deficit on the biochemistry, anatomy, and yield components of cassava.