THE EFFECT OF PLANT POSITION ON ROOT DEVELOPMENT AND VEGETATIVE GROWTH IN AEROPONIC LETTUCE

Sowing was made on 3.2.92 in cubes of rockwool and the plants were transplanted on 11.3.92. They were arranged in four rows on 2 sq m polystyrene panels inclined 50°, with a plant density of 12 per sq m of panelling or 20 per sq m of plot. The fertilizer solution was distributed by mist sprayers placed in the tunnel formed by the two panels.

The results obtained showed that the development of the plants was affected by their position on the panel. The mean root length of the plants placed along the four rows decreased gradually from top to bottom (21.19 – 19.44 – 16.42 – 5.53 cm)

Total yield showed the same trend: 8.34 – 8.53 – 7.84 – 5.46 kg/sq m of plot in the first, second, third and fourth rows respectively.

The general results show a close correlation (r = 0.797) between mean root length and mean weight of the head as well as a less significative correlation (r = 0.720) between the mean dry weight of the roots and that of the heads.

Diverse parameters could have affected these results as other authors have pointed out in other species. It is believed in fact that the difference in root development could have been affected by the difference in height from the ground, by the formation of a thermal gradient or by the difference in the distance between the plants and the mist sprayers.

It is possible that the difference in light intensity could have affected the development of the aerial part of the plant.

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