NUTRITIONAL REQUIREMENTS OF THE EDAPHIC ECOTYPES IN MELILOTUS ALBA MEDIC.

Abstract

SummaryThe present study deals with the nutritional requirements of the two edaphic ecotypes—(i) the ‘calcareous’, growing on a calcareous soil and (ii) the ‘acidic’, growing on an acidic soil. The germinability of the seeds was found to be inherently different for the two populations. The seeds of the ‘acidic’ population were found to do better in an acid medium and the reverse was found to be the case for the ‘calcareous’ population. Significant differences were noted with regard to the accumulation of calcium and other nutrients under different calcium levels and pH conditions. The ‘acidic’ population always showed a better accumulation of calcium, except at high calcium levels; it also showed a greater ability to accumulate other nutrients like potassium and phosphorus. The adaptive significance of such a behaviour is discussed. A differential response to phosphorus was noted between the two populations, the ‘acidic’ type showing an improved growth yield at higher phosphorus levels whilst that of the ‘calcareous’ type was insensitive. For the same level of phosphorus in the medium, phosphorus accumulation decreased for the ‘acidic’ type at pH 7 in a calcareous medium compared with accumulation in a non‐calcareous medium. For the ‘calcareous’ population, accumulation improved in an alkaline medium. Whilst the accumulation of phosphorus was little affected by change in phosphorus concentration in the medium for the ‘calcareous’ population, the ‘acidic’ type showed improved accumulation with increase in phosphorus level in the medium. The significance of these effects is discussed and it has been shown that besides the direct role of calcium itself, pH with the accompaniment of changes in the availability of phosphorus could be responsible for the restriction of these ecotypes to their respective habitats.