Studies on Edaphic Ecotypes in Euphorbia Thymifolia L.: II. Growth Performance, Mineral Uptake and Inter-Ecotypic Competition

Abstract

The three populations within the red ecotype of Euphorbia thymifolia showed very diverse responses to calcium in the soil in regard to their growth performance under competitive and non-competitive conditions. In nature these populations occupy soils with markedly different levels of exchangeable Ca in the soil. Malla soil was found to be highly calcareous compared to Chandigarh soil, Shiwalik soil being intermediate. The differences recognized in the growth yield of the three populations are maintained when grown on a neutral substratum. The Malla population yielded less than the Shiwalik and Chandigarh populations. The Chandigarh population gave maximum yield. A close correlation has been shown to occur between the yields of the three populations and the habitats they occupy in nature. Thus, the yield of Malla population increased with increase in soil Ca level while that of Chandigarh population showed a marked decrease in calcareous soils,, Shiwalik population showed an intermediate response to Ca. The three populations showed different capacities to accumulate different minerals, when grown on a neutral substratum. A close correlation was recognized between Ca uptake and the natural habitat conditions they occupy. Thus, the Malla population showed a consistently high level of Ca in the plant tissue compared to the Chandigarh population in both calcareous and non-calcareous soils. The Chandigarh population showed a low level and the Shiwalik population was intermediate between the other two. The Malla population showed an increase in Ca uptake with increase in soil Ca whereas the reverse was the case with the Chandigarh population. Differential response to soil Ca was also recognized in the uptake of K, Mg and P by the three populations. The results indicate the occurrance of at least three edaphic ecotypes within the red ecotype of Euphorbia thymifolia L.