Variation in Root Morphological and Physiological Traits and Nutrient Uptake of Chickpea Genotypes

ABSTRACT

Plant nutrients such as potassium (K), phosphorus (P), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) mostly remain fixed in soils and their bio-availability to plant roots is diffusion-limited. Hence, superior root traits, that can enhance their dissolution and capture from the soils, can play a central role in its productivity. Root morphological (root length and root hairs) and physiological traits (root exudation of protons and phosphatase enzymes) of ten selected varieties/breeding lines of chickpea (Bari-chhola-3, Bari-chhola-4, Bari-chhola-5, Bari-chhola-6, Bari-chhola-7, Bari-chhola-8, BGM-E7, ICCV-98926, ICCV-94924, and ICCV-98916) were studied and related them to the uptake of the nutrients in a pot experiment.

There were significant (P < 0.05) genotypic differences in root length (RL) and root hair length (RHL). The RL ranged between 70 m plant^{? 1} and 140 m plant^{? 1}. The variation in RHL was significant (P < 0.05) and it ranged between 0.58 ± 0.09 mm (Bari-chhola-5) and 0.26 ± 0.09 mm. The root hair density (RHD, number mm^{? 1}root) varied between 13 ± 2 and 21 ± 3 among the genotypes. The presence of root hairs increased the effective root surface area (e.g., Bari-chhola-5) up to twelve times. The genotypes differed in their ability to acidify the rooting media in laboratory agar studies, with Bari-chhola-5 inducing most acidification followed by Bari-chhola-3. The ability of Bari-chhola-5 to acidify the rhizosphere was also confirmed by embedding in situ roots in the field in an agar-agar solution containing pH indicator dye Bromocresol purple. The genotypes did not differ for induction of acid phosphatase activity (Aptase) in the rooting media. The genotypes inducing greater acidification and possessing prolific root hairs (Bari-chhola-3 and Bari-chhola-5) absorbed significantly higher amounts of the nutrients K, P, Fe, Mn, and Zn, whose availability in soils is usually low. The results suggest that a collective effect of superior morphological and physiological root traits confers better nutrition of chickpea genotypes in low-nutrient soils.