DEPENDENCE OF TRANSPIRATION INTENSITY AND GROWTH PROCESSES ON THE MICROCLIMATIC CONDITIONS UNDER POLYETHYLENE COVERS
Until now the investigations have mainly been carried out on the obtained yield, which is correct, though not sufficient. Data, with the respective analyses, helping towards a more comprehensive elucidation of the growth processes, have proved expedient. The analyses of these processes render possibilities of studying the increment of the vegetative mass of the plant and for assessing not only the whole plant's production, but also the production of separate parts of the plant.
The works of Watson (1952, 1958), Evens-Hews (1962), Nichiporovich (1961, 1963) and others on the above problem have become quite popular lately. As early as 1932, Boysen and Ensen have suggested that to determine solely the production of a plant means to leave the investigation half finished. This production should be studied as well. The results presented below were obtained with the RSK cultivar, the latter being suitable both for early production in greenhouses and in the open. The planting scheme was 50 x 30 cm. The overall dimensions of the tunnels were 10 x 3.5 x 1.9 m. The test was conducted in the following variants:
- Control (in the open).
- Under polyethylene covers.
Once every 8 to 10 days, whole plants were picked to be analyzed. The mean values of the dry matter W (according to Kwet-Necas-Smetankova, 1966), the assimilating surface A of the leaves, the relative rate of growth R (RGR), the productivity C, the relative foliage F, and the shading of the soil by the leaves L (LAJ) were determined.
The mean dry matter increment is derived from the equation of Blackmuck, namely:
where W2 and W1 are the dry matter values of two consecutive pickings, while t2, t1 are time intervals. The increase in production per unit area is derived from the following equation: C = (W2-W1).(t2-t1)-1.p-1, where p = the soil area corresponding to the given dry matter weight. The relative foliage (F) designates the leaf surface to the total dry matter weight ration, i.e., F =A/W. The shading of the soil by the leaves designates the leaf surface to a determined soil area ratio (for a certain moment), i.e. L = A/P.
Of the climatic factors, the temperature and the air humidity were studied.