Effect of Photoperiod and Temperature on Brassicaceae Family Plant Metabolism and Growth

Abstract

The experiments were carried out in the phytotron complex of Plant Physiology Laboratory of the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. The objective of our studies was to investigate the influence of photoperiod and temperature on radish (Raphanus sativus L.) and rocket (Eruca sativa L.) growth parameters, photosynthetic pigments and primary photosynthesis metabolites. Radish ‘Faraon’ and rocket ‘Rucola’ were grown in boxes in a peat substrate (pH 5–6) mixed with sand in the ratio of 3:1. The plants were grown in a greenhouse at 21-25 / 15-18○ C (day / night) temperature. Sprouted plants were transferred to four phytotron chambers, with controlled temperature and photoperiod conditions: 1) + 10/14○ C (night / day) and 8 hours (photoperiod); 2) + 10/14○ C and 16 h.; 3) + 17/21○ C and 8 h.; 4) + 17/21○ C and 16 h. Plants were irradiated with high-pressure sodium lamps (HPS). Total photosynthetically active radiation photon flux density of analyzed light combinations were ~160 μmol cm2 s-1. Plants from planting to technical mature stage were grown for 30 days. Our results showed that the Brassicaceae family plants, radish and rocket formed four or more leaves, were elongated and accumulated more dry and green mass and radish formed the biggest roots at 17/21○ C (night / day ) and 16 h photoperiod. Lower, 10/14○ C (day / night), temperature regime suppressed the growth of tested plants. Radish and rocket were more compact and had less leaves but the highest content of chlorophyll a and b and the ratio of sugars (fructose, glucose and sucrose) was determined in the leaves at 10/14○ C and 16 h photoperiod. Direct correlations between the biochemical and biometric indices were established.