Effect of auxins on root quality and anatomical integrity in tissue-cultured date palm (Phoenix dactylifera L.) cv. Mirhaj

Document Type : Research Paper

Authors

1 Horticulture and Landscape Gardening Department, ‏College of Agriculture, ‏University of Diyala, Diyala, Iraq

2 Environmental Biotechnology Department, Biotechnology and Environmental Center, University of Fallujah, Fallujah, Iraq

3 Horticulture and Landscape Gardening Department, ‏College of Agriculture, ‏University of Baghdad, Baghdad, Iraq.

4 Center for Environmental Research, University of Technology Baghdad, Baghdad, Iraq.

Abstract

Objective
Rooting represents a crucial phase in the micropropagation of date palm, and root quality is an important determinant of successful plantlet establishment. This study aimed to investigate the effects of two widely used auxins, indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA), on rooting efficiency, root morphology, and anatomical structure in tissue-cultured date palm (Phoenix dactylifera L.) cv. Mirhaj. Special attention was given to identifying root malformations associated with different auxin types and concentrations, as well as understanding their anatomical characteristics.
Materials and methods
The experiment was conducted in 2024 using shoots derived from indirect somatic embryogenesis of cv. Mirhaj. Uniform shoots at the elongation stage were selected and cultured on full-strength semi-solid Murashige and Skoog (MS) medium supplemented with IBA or NAA at concentrations of 0.1, 0.25, and 0.5 mg L-1. Six treatments were arranged in a completely randomized design with fifteen replicates per treatment, where each shoot represented one replicate. Three shoots were cultured per 380 ml bottle containing 50 ml of medium. Cultures were maintained under controlled environmental conditions. After eight weeks, data were collected on rooting percentage, number of roots per shoot, root length, secondary root formation, and incidence of root malformations. For anatomical analysis, cross-sections of healthy and malformed roots were prepared, fixed in 70% ethanol, stained with safranin and fast green, and examined under a light microscope.
Results
Auxin type and concentration significantly influenced rooting performance and root morphology. NAA at 0.25 and 0.5 mg L-1 produced the highest rooting percentage (90%) and increased the number of roots per shoot. In contrast, IBA at 0.1 mg L-1 resulted in the longest roots, indicating better elongation capacity. However, higher concentrations of NAA led to shorter roots and a marked increase in root malformations, reaching 50% at 0.5 mg L-1. No malformations were observed with low IBA concentrations. Anatomical analysis revealed severe structural abnormalities in malformed roots, including disrupted vascular tissues and irregular cellular organization.
Conclusion
The findings highlight a trade-off between rooting efficiency and root quality. While NAA improved rooting percentage, it negatively affected root structure. Low-concentration IBA, particularly 0.1 mg L⁻¹, promoted longer roots with no observed malformations under the conditions tested, suggesting its potential suitability for producing morphologically and anatomically sound roots.

Keywords

References

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Agricultural Biotechnology Journal
Volume 18, Issue 4
August 2026
Pages 525-538

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