Effect of Low Temperatures in Carbohydrates Accumulation On Garlic Leafs (Allium sativum) During Their Development

The fructans constitute 70% of the dry matter of garlic bulbs, these are polymers of fructose linked at one sucrose molecule; the primary sugars are synthesized in the leaves, transported and accumulated in the bulbs. This process is influenced by the thermo-photo period, indicating that low temperatures and short photoperiod at the beginning of plant development improve the bulbs quality and a greater fructans accumulation. Not known as the initial thermal-photo period modifies the metabolism and accumulation of fructans in garlic. We studied the effect of low temperatures and short photoperiod in the development plant and in the content of sugars and fructans in garlic leaves. Garlic bulbs CV 'California Late' were stored 4 weeks at 10 ° C, and their cloves planted in pots and grown 30 days at different environments controlled: A) 13h/0 °C in darkness and 11h/16 °C in white light; B) 13h/5 °C in darkness and 11h/16 °C in white light; C) 13h/10 °C in darkness and 11 H/16 °C in white light; D) 13h/22 °C in darkness 11 h/22 °C in white light. Later, the thermal photo period of A, B and C were changed at 11h/10°C in darkness and 13 h/22 °C in white light. The experiment D (22 ° C) remained at the same temperature but changing its photoperiod (13h light and 11h darkness). Under these latter conditions, three plants were taken periodically and the weight of the canopy, number of leaves per plant and the glucose, fructose, starch and fructans contents in the second leaf of each plant were registered. Plants at 0 °C showed greater total and canopy weight and more leaves (12) than plants grown at 5 and 10 °C (9). After 109 days after sowing (DAS), the fructans content was larger (28 g/100 g) in plants at 0 °C than plants grown at 5 °C (24 g/100g) registered at 95 DAS; also the starch content was higher (6 mmols starch/mm²) at the 118 DAS respect of plants grown at 5°C (4 mmols starch/mm²); out of those days did not be detected starch in all experiments. At 10 °C lower contents of fructans were observed without starch accumulation; plants grown continuously at 22 °C did not show starch or fructans accumulation. Throughout the growing cycle at 10 ° C, the sucrose was detected but not glucose or fructose, indicating possibly a high activity of sucrose synthesis.