The Effect of Sun Light Intensity on the Growth of Azolla Nicrophylla and its Symbiont Anabeana Azollae in Brackish Water

Abstract

Azolla microphylla is is a tropical and subtropical fern with a length of 1.5-2.5 cm that can be used as an organic fertilizer so that it can meet nutrient needs, especially for plants. The fern has a simbiont Anabaena azollae which can fix N2 freely in the air so that it can contribute to the need for N for plants in the soil. This research is aimed to study the effect of sunlight intensity on the growth of A. microphylla and its symbiont An. azollae in brackish water. A two factors (factor a; light intensity and factor b; duration of cultivation) completely randomized design was applied to the experiment. Sunlight intensity composed of 0, 30, 50, 70 and 100 %. Duration of cultivation consisted of 0, 7, 14, and 21 day. Every unit of experiment was setted in a 100 × 100 × 20 cm plastic coated wood box, filled with brackish water of 3 ppt salinity up to 15 cm depth and 1 kg fermented cow dung, mixed gently and seeded with approximately 1 gram of fresh A. microphylla. Every box was covered with some pieces of wood based on its light intensity. Growth of the fern was measured by counting the number of the fern colony directly and weighted with analitycal balance. While growth of An. azollae were counted by using sedwick rafter counting cell. It is concluded that the sunlight intensity significantly influences the growth of A. microphylla and its symbionts An. azollae. The best sunlight intensity was 70%. A dinamic growth recorded during the first week post inoculation in which dobling time toke place. It is recomended to grow A. microphylla and its symbionts An. azollae under 70 % of the sunlight intensity