Ultrastructural response of wheat (Triticum aestivum L.) lines to potential allelopathy of Alstonia scholaris (L.) R. Br. leaf extract

An investigation was carried out to evaluate the impact of the allelopathic effect of Alstonia scholaris leaf extract on morphoanatomical and physiological characteristics of 5 wheat lines. Three extract dilutions were prepared, viz. 0 (control), 15 and 30% of the aqueous extract and sprayed on wheat lines (3094, 5066, M5082, 7076 and A2011) at 15-day intervals until maturity from November 2017 to May 2018. All wheat lines responded differently to an allelochemical extract of A. scholaris. Disintegration of root parenchyma and transformation of stem chlorenchyma to sclerenchyma in stems were noted in Line 3094. Increased sclerification in the root cortex (141.7-212.5 mu m) and stem hypodermal region (212.5-354.2 mu m) was recorded in Line 5066. Line M5082 showed intensive sclerification in the root cortex and vascular region, and around stem vascular bundles along with a significant decrease in leaf thickness. Line 7076 was the most sensitive genotype showing significant reduction in the stem (1402.8-821.8 mu m) and root area (963.5791.9 mu m) and leaf thickness (1346.2-396.8 mu m). Line A2011 responded very differently by increasing proportion of parenchyma and sclerenchyma. A low concentration (15%) of allelochemical extract promoted growth and development and a high concentration (30%) was toxic, causing growth retardation and tissue damage.