BIOLOGICAL PARAMETERS FOR A CHARACTERIZATION OF GREENHOUSE MICROCLIMATE

With the expensive species like roses, chrysanthemum and tropical plants a reduction of the night-temperature level from 16 to 12–13°C results in a 40% economy.

The programs started in 1974. The first results of the low temperature programs seem to possess the same zero-growth temperature point as normal selections (gerbera in growth-cabinets). Lower zero-growth would be welcome.

A complete double-skinned glazing with plastic film gives an economy of 30 to 40% of the fuel, linked with a loss of 10–15% of the light transmission. It is assumed that the wanted genotypes may tolerate the night temperature reduction, the limited light reduction and the microclimatic conditions of the double-glazed greenhouse with the same yields, quality and earliness. It would induce a very important cumulative economy of heating energy. Furthermore, if the plants exhibit a wide tolerance to light conditions, the double glazing could be reinforced for a better insulation with varieties selected in low-light conditions.

At the moment, the selection is carried out with plants grown in limiting conditions, as severe or more severe than the conditions applied in cultivation: for a winter crop at 13°C minimal temperature, screening is done in the normal model of greenhouse with 13 or 12°C set-temperatures.

One question is to find criteria for the adaptation of plants to such severe conditions, which could be observed even in more normal conditions of growth: it would allow a much cheaper development of the breeding programs, or the screening of a larger number of individuals. Criteria for a selection at very early stages are also very useful, and less problematic.

The biological parameters of use for the breeder are principally non-destructive, realizable in hundreds of measurements, with a limited and simple equipment; it can, with slight modifications, be applied to the different groups of ornamental crops (short-lived with reduced storage, like snapdragon or chrysanthemum, bulbs, woody perennials with storage, pot-plants, foliage plants).

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