The influence of temperature, light, salinity and seed pre-treatment on the germination of Sesbania sesban seeds

The germination of Sesbania sesban seeds was studied under controlled environmental conditions. Interactive effects of temperature and light, effects of salinity and effects of different pre-treatments ofseeds were studied. Sesbania seeds were placed in Petri dishes with filtration paper and the germination and radical development followed during seven day periods. The seeds generally germinated within one or two days. There was no difference in percent germination between dark and light treatments, but the development of radical length was significantly influenced by both light conditions and temperature. Germination was highest at 30 and 37ºC (up to 85%) but seeds alsogerminated readily at 22ºC. No germination was observed at low (5 and 13ºC) and high (45ºC) temperatures. Salinities up to 100 mM NaCl (5.8 ppt) did not influence the germination percentage, butat 200 and 250 mM germination was reduced to 29 and 17% respectively. Pre-treatment of seeds in hot water, sulphuric acid or calcium sulphate had only minor effect on germination rate. The results are consistent with S. sesban being an opportunistic tropical wetland species capable of establishing itself in a wide range of environmental conditions

Leaf vegetables for use in integrated hydroponics and aquaculture systems: Effects of root flooding on growth, mineral composition and nutrient uptake

In recirculating aquaculture and hydroponics systems, the waste products from fish production are used to produce vegetables or other crops of economic value, and the water is recirculated to the fish tanks. We studied growth, productivity and nutrient uptake of four leaf vegetable species (Lactuca sativa, Ipomoea aquatica, Brassica rapa var. chinensis and Brassica rapa var. parachinensis) in a controlled growth experiment with three root flooding treatments (drained, half-flooded and flooded) toassess their preferred hydroponic growth requirements, biomass production and nutrient removal capacities. Growth of the two Brassica varieties was clearly best at drained root conditions, while L. sativa and I. aquatica grew best with half-flooded and flooded roots. I. aquatica took up 3 times more N, P and K per plant than L. sativa, and 4 to 6 times more than the two Brassica varieties. At a plant density of 30 plants/m2, I. aquatica produced 146 g DW/m2 aboveground biomass during a 30-day cultivation period containing 2.8, 0.9 and 6.8 g/m2 of N, P and K, respectively. L. sativa produced 115 g DW/m2 of aboveground DW during a 60-day cultivation period, containing 2.2, 0.6 and 4.6 g/m2 of N, P and K, respectively. The two Brassica varieties produced much less aerial biomass (50-54 g DW/m2 during a 60-day period). Both I. aquatica and L. sativa are promising species to be included in integrated hydroponic and aquaculture facilities, with I. aquatica showing the most promise because of its higher growth and nutrient uptake capacity

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