Induction of the Growth of Green Oak (Lactuca sativa var. crispa L.) Using N2 Fixing Cyanobacteria via Ultrasonic Treatment

Abstract

This research studied the application of ultrasonication to induce growth and co-cultivate N2-fixing cyanobacterium (Nostoc sp. TUBT05) and green oak (Lactuca sativa var. crispa L.). The roots of one-week seedlings were sonicated for 20, 30, 60, 300 and 600 seconds and transferred to BG-11N0 medium with and without Nostoc sp. TUBT05. After one week, the roots of green oaks from each treatment were examined under a light microscope. The colonization of Nostoc sp. TUBT05 filaments on the root surface and tissues
was observed and cyanobacterial chlorophyll a content was measured. The results showed that there were Nostoc sp. TUBT05 filaments colonized on the epidermal root surface and penetrated into cortex tissue with high quantity of cyanobacterial chlorophyll a content in treatment with sonicated root and soaked in BG-11N0 + Nostoc sp. TUBT05. All remaining seedlings were planted and cultured for 15 and 28 days. Green oak growth was measured from fresh and dry weight of leaves and roots and also the width and length of the leaves. There were significant differences between the green oak growth at 15 and 28 days among the treatments (p < 0.05). Roots sonicated for 300 s and soaked in BG-11N0 + Nostoc sp. TUBT05 (T11) at 15 days showed the highest growth of leaves in terms of both the fresh and dry weights (7.77 ± 0.07 and 0.20 ± 0.01 g), root fresh and dry weights (1.30 ± 0.06 and 0.07 ± 0.00 g), and leaf width (4.66 ± 0.07 cm). The leaves at 28 days from T11 showed the highest growth in terms of the fresh and dry weights (12.80 ± 0.14 and 0.70 ± 0.00 g), root fresh and dry weights (1.90 ± 0.03 and 0.11 ± 0.00 g), and leaf width (6.21 ± 0.07 cm). This study indicated that the application of ultrasonication on root significantly increased the growth of green oak and could induce an effective symbiosis between Nostoc sp. TUBT05 and green oak.