Kinetics of Zinc Uptake and Anatomy of Roots and Leaves of Coffee Trees as Affected by Zinc Nutrition

ABSTRACT

Zinc (Zn) uptake kinetics and root and leaf anatomy were studied in coffee trees grown in nutrient solutions with or without Zn. Leaves and roots were sampled and cuts were made in the medium part of the leaves and in root tips and observed under an optical microscope. Plants grown without Zn showed an increase in root and in root stele diameter. There was also an increase in epidermis thickness and in the cross-sectional area of the cortex and stele due to Zn deficiency, but the diameter of xylem vessels was decreased. An increase in root cortex and stele diameter provided for an increased surface for nutrient uptake. Accordingly, C_min was decreased from 13.8 to 3.4 μ mol L⁻¹ and V_max increased from 0.50 to 2.1 μmol cm⁻² h⁻¹.

Keywords:

• Coffea arabica
• nutrient deficiency
• nutrient uptake
• root anatomy
• zinc

Notes

*Significant (P < 0.05);

**(P < 0.01).

*after 24 hours;

** after 36 hours.

***Values expressed in μ mol cm⁻² h⁻¹.

*Difference between the first and last samplings.