Root Anatomical Traits and Their Possible Contribution to Drought Tolerance in Grain Legumes

Ramamoorthy Purushothaman,Mainassara Zaman-Allah,Nalini Mallikarjuna,Rajaram Pannirselvam,Lakshmanan Krishnamurthy,Cholenahalli Lakkegowda Laxmipathi Gowda

doi:10.1626/pps.16.1

Ramamoorthy Purushothaman, Mainassara Zaman-Allah + Show 4 more

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https://doi.org/10.1626/pps.16.1

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Abstract

Legumes are mostly grown rainfed and are exposed to various types of drought ranging from terminal drought to intermittent drought. The objective of this study was to compare the root anatomy of six major legume crops in relation to their drought adaptation strategies. Plants of chickpea (Cicer arietinum L.), groundnut (Arachis hypogaea L.), pigeonpea (Cajanus cajan [L.] Millsp.), cowpea (Vigna unguiculata L. walp.), soybean (Glycine max [L.] Merr.) and common bean (Phaseolus vulgaris L.) were grown along with pearl millet (Pennisetum glaucum [L.] R. Br.) in a Vertisol field during the rainy season of 2010. Four root segments from 35-day-old plants of each crop species were collected, 10 cm from the root tip and used for making transverse sections. These root segments were thinner in both groundnut and pigeonpea than in other legumes but similar to those of pearl millet. Soybean and pigeonpea had a relatively thinner cortex than the other legumes. Xylem vessel size and the numbers were apparently the most discriminating traits of legumes. Pigeonpea is equipped to conduct small quantities of water per unit time with a few narrow xylem vessels and that explains the conservative early growth of pigeonpea. Chickpea and cowpea showed moderate xylem passage per root indicating that they are capable of absorbing water moderately and are well equipped for regular drought episodes. The development of cortical and stele tissue and their proportion is markedly influenced by moisture availability to the root system.

Highlights

Legumes are mostly grown rainfed and are exposed to various types of drought ranging from terminal drought to intermittent drought
Groundnut and pigeonpea had the least prolificacy of the root system
One of the most functional aspects related to root anatomy is water and nutrient transport capacity, because it is highly influenced by the number and size of the water conducting elements (Esau, 1965; Steudle and Peterson, 1998)

Summary

Introduction

Legumes are mostly grown rainfed and are exposed to various types of drought ranging from terminal drought to intermittent drought. Crop plants respond to variations in water and oxygen status of the soil through morphological, anatomical and physiological adjustments that help them cope with such variations and the associated stress (Krishnamurthy et al, 1998, 1999; Chandler and Bartels, 2008) This capability may have high adaptive value in plants in an environment with frequent episodes of drought. Plant Production Science Vol.16, 2013 grain yield and seed quality (Upreti et al, 1997) These crop species may have different adaptive mechanisms to drought at various organizational levels including morphology, anatomy and physiology due to differences in growing season and the agro-ecological conditions of the growing environments. The roots of some monocotyledons, like corn, have a medulla as well as a vascular cylinder (Vasquez, 2003)

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