Effect of fruit growth, temperature and irradiance on biomass allocation to the vegetative parts of cucumber

Cucumber plants were grown in a greenhouse at 18 or 25 degrees C with four intensities of fruit removal (1 fruit remaining for every 1, 3 or 6 leaf axils, or all fruits removed) or at three different levels of irradiance (shading with cheesecloth to give 100, 50 or 30% transmittance) in order to analyse the effects of fruit growth, temperature and irradiance on the dry matter allocation to leaves, stems, petioles and roots. With increasing irradiance, the dry weight of the vegetative part of the shoot increased, but the proportion of the total dry matter distributed to this part decreased. An increase in irradiance enhanced stem dry matter production less than leaf and petiole dry matter production which was in turn less stimulated than root dry matter production. In fruit-bearing plants, an increase in temperature had no effect on the dry matter allocation to the leaves, stems and petioles, but reduced the allocation to the roots. Fruit growth strongly reduced dry matter production of all vegetative plant parts, but the distribution between stems, leaves and petioles was only slightly affected. At 25 degrees, the dry matter distribution between the roots and the vegetative part of the shoot was not affected by fruit growth, but at 18 degrees, the root to vegetative shoot dry weight ratio decreased with increasing number of fruits on the plant. The biomass allocation between roots and shoot is discussed in relation to the functional equilibrium concept