Growth Responses of Calendula (Calendula officinalis L.) to Temperature Regimes and Different Soil Types.

Temperature stress is the major environmental regime that affects agricultural production worldwide, especially in arid and semi-arid regions. Arid and semi-arid regions are characterized by highly variable environmental conditions were temperature goes extremely low to extremely high and affects the performance, physiology and biochemistry of the plants. This research investigated the effect of temperature regimes on sowing seeds of Calendula officinalis L. at (1, 15 September and 1, 15 October, 2013 and 2014) grown in different soil types (clay, loamy, sand and mix between them). Significant increases in vegetative growth characters were observed for plants cultivated in sandy soil compared to those cultivated in clay loamy or mixed soils. The best result was obtained with 15 September treatment sandy soil plants. This result included higher branches number and leaf area, higher shoot fresh and dry weights, as well as higher number of flowers. Physiological traits include transpiration rates, stomatal conductance, intercellular CO2 concentration and sample cell H2O, were highly significant in first October planting date with clay loamy soil type in both seasons. Environmental regimes and different soil type’s showed clear effects on the biochemical contents (total soluble protein, H2O2 and catalase activity fractions of the leaves) of three week old seedlings. It is concluded that sowing in September in sandy soil is recommended for Calendula production in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]