Aquatic vascular plants generally have aerenchyma, plant tissue containing enlarged gas spaces, in order to survive in long-term flooding environment. We collected 25 species of aquatic plants, which are belonged to Polygonum, Persicaria, Euryale, Nuphar, Nelumbo, Ceratophyllum, Trapa, Oenanthe, Nymphoides, Limnophila, Typha, Potamogeton, Sagittaria, Hydrilla, Vallisneria, Ottelia, Phragmites, Scirpus, Acorus, Monochoria from south Korea, and performed anatomical analysis to elucidate the characteristics of aerenchyma pattern in aquatic vascular plants. As a result, if belonged to the same family, aquatic plant species seem to share similar patterns of aerenchyma. Several patterns of aerenchyma such as schizogeny, expansigeny and lysigeny radially or tangentially are found among aquatic plants. Especially, in our results, Nymphoides peltata, Nymphoides indica, Typha orientalis, Typha latifolia, Phragmites australis and Monochoria korsakowi have two types of aerenchyma, lysigenous aerenchyma and schizogenous aerenchyma or lacunae. However, other species have only one type of aerenchyma; schizogeny or lacunae.
Aerenchyma of Trapa is significantly enlarged in petioles even though they contact with the air of water surface. The petioles have the highest porosity in Trapa japonica - leaf: 24.9%, petiole: 62.7%, stem: 20.0%, submerged root: 13.9%, subterranean root: 15.1%, seminal root: 10.0%
Phragmites australis has structural advantages of the internal aeration via rhizome and lysigenous aerenchyma which make possible to survival in flooding environment. In general, plant response to oxygen deficiency involves increase in the expression of alcohol dehydrogenase (ADH) and RHO-like small G protein (Rop) activation. Rop signaling is reported to be involved in regulating ADH expression in response to oxygen deficiency. To study which genes are associated with aerenchyma formation, we have cloned three partial cDNAs, ADH, Rop and SUS (sucrose synthase). The size of clones are 1.6 kb, 367bp, 650bp; each ADH, Rop and SUS. The RT-PCR results show that the expression of three genes increase in submerged condition.
