Root Development and Source-Sink Relations in Carrot,Daucus carotaL.

Publisher Website
Google Scholar
Abstract
Growth analysis and 14CO2 feeding experiments have shown that the developing storage organ became an increasingly important sink for assimilates, accumulating 40% of the dry matter produced by the carrot plant within 9 weeks of sowing. The relative importance of each leaf in fixing and exporting 14C was assessed at two stages of development. Morphogenetic responses indicated that an absence of thickening in the lateral roots was associated with continued meristematic activity in the tap root, in the form of an elongating apex or a vascular cambium. Source-sink relations were examined by observing plant growth following the removal of part of the tap root and/or lateral roots. Pruning the roots at 35 d reduced the subsequent growth of the plant by reducing the AGR of the remaining root system and the shoot. The reduction in leaf growth was associated with a loss of fibrous roots, removal of part of the tap root having very little additional effect on shoot growth although the AGR of the root system was reduced by a further 78%. Increased fibrous root RGRs following pruning soon re-established the normal fibrous root/shoot ratio. These experiments demonstrated the importance of the root system in controlling dry matter production in the carrot plant, but suggested that the sink activity of the developing storage organ was less significant than other root functions.