Lateral root development in exotic cottons

Abstract

Lateral root development and vascular bundle arrangements of young 7-day-old seedlings of 120 exotic cotton ( Gossypium hirsutum L.) strains were evaluated to determine the relationship between the number of vascular bundles in the taproots and the observed lateral root branching. Seeds were germinated and seedlings were grown in polyethylene growth pouches at constant temperature (30°C) in the dark for 7 days. Taproot length, lateral root length and number of lateral roots were evaluated on a daily basis during the 7-day measurement period. The vascular bundle arrangement of each taproot was determined by examining a segment of the taproot 5 cm from the root apex with a light microscope at the end of the 7-day period. Significant differences in the lateral root development among strains were noted. An in-depth presentation of the root development of four strains (T25, T169, T256 and T165) indicated that partitioning of total root length into lateral root was (Anov and Duncan's Multiple Range Test) significantly higher for the T25 and T256 strains relative to the T169 and T165 strain. Branching intensity was shown to be dependent on the vascular bundle arrangements as indicated by the Chi-square analysis of the relationship between the number of vascular bundles present in the aproots and the branching intensity (No. lateral roots per cm of taproot). As the number of vascular bundles increased, the proportion of plants with high branching intensities also increased. This information may possibly be useful in genetically altering plant rooting patterns and improving water and nutrient utilization under adverse growing conditions.