Responses of Lens esculenta Moench to controlled environmental factors

<p/>Many experiments were undertaken to study the responses of the lentil cultivars 'Large blonde' and 'Anicia' to controlled environmental factors. They covered different aspects of the physiology and the ecology of the crop.<p/>The orientation experiments (2) involved germination and depth of sowing. The optimum temperature range for the germination of 'Large blonde' was 19-29 °C whilst that of 'Anicia' was 21-25 °C. The depth treatments (1, 4 and 8 cm) caused no particular effects on flowering and stem elongation. They brought about a general linear response of the cultivars with respect to average leaf production (Fig. L) The 4-cm treatment appeared to be the most favourable for dry matter production. A temperature of 23°C and a depth of 3 cm were used to pregerminate and sow the seeds respectively in carrying out further experiments.<p/>Studies on the photoperiodic requirements of the cultivars (3) led to differences between 'Large blonde' and 'Anicia'. The first cultivar behaved as a qualitative long- day plant: it did not flower at photoperiods shorter than 14 hours. 'Anicia' reacted quasily as a day-neutral plant. It flowered under all the photoperiods (8-16 hours) used, but came somewhat earlier into flower at 15 and 16 hours. The dry matter production of the cultivars seemed not to be influenced.<p/>The effects of the following temperature regimes: 9°C (night)-15°C (day), 13°C (night)-19°C (day), 17°C (night)-23°C (day), 21°C (night)-27°C (day), 25°C (night)-31°C (day) and 29°C (night)-35°C (day) on the plants of both cultivars were investigated (4). The treatment 21-27°C (average 24°C) led to the maximum leaf production, stem length and dry matter production. The regime 29-35°C was particularly detrimental to the growth of the cultivars: the plants were prematurely harvested before death occurred.<p/>An experiment was also conducted on daily amplitudes of temperature (5). It was carried out with three temperature regimes: 18 °C (night)- 30°C (day), 21 °C (night)- 27°C (day) and constant 24°C. The amplitude of 6°C (21°C-27°C regime) led to the highest average stem elongation, leaf and dry matter productions.<p/>The photosynthesis of 'Large blonde' and 'Anicia' was not influenced in a definite way by the (instantaneous) temperatures of 18°C, 24°C and 30°C (6). The photosynthetic capacity of the cultivars was similar. The surface they formed per unit dry weight was different, the ratio leaf area (dm <sup><font size="-1">2</font></SUP>)/dry weight (g) of 'Anicia' being higher than that of 'Large blonde'.<p/>The study of the drought tolerance of the cultivars under four frequencies of watering (3, 4, 8 and 12 times a month) brought out treatment-dependent differences in leaf area, stem elongation, dry matter production and evapotranspiratio (7). These features increased with a raise of the level of watering. The final water content of the plants was not clearly affected by the regimes.<p/>The tolerance to salinity and exchangeable sodium (in terms of ESP) was also brought under investigation (8). The cultivars were subjected to the influence of four salt concentrations corresponding with 1.2,4.5,8.4 and 13.1 mmhos/cm. In general, increase in the salt concentration resulted in an increased reduction of stem length and dry matter output. This depressing effect of salt was coupled with a continuous accumulation of Na and Mg in the plants. The tolerance limits of the cultivars were found to be between 8.4 and 13.1 mmhos/cm.<p/>The cultivars responded also clearly to the following ESP levels: 0.48, 4.53, 6.63 and 9.98. The higher the ESP level was, the larger became the growth reduction and the Na accumulation.<p/>Data on the growth and development patterns of 'Large blonde' and 'Anicia' were recorded in the course of an experiment which lasted 16 weeks (9). Both cultivars showed their greatest relative growth rate (RGR) between the second and the fourth weeks after sowing (0.81 g/g/week for 'Large blonde' and 0.85 for 'Anicia'). The final dry matter yields per plant of 'Large blonde' and 'Anicia' were comparable (4.7 and 4.5 g respectively). The seeds of the first cultivar represented 11 % of the final dry matter of the plant whilst those of the second accounted for 24 %. The highest shoot/root ratios (4.7 and 6.3 for 'Large blonde' and 'Anicia' respectively) were registered at the conclusion of the experiment