Aquatic plants resort to vegetative reproduction more frequently than do land plants, although methods of propagation are fairly universal. The uniform environment and abundance of carbon dioxide and water encourage leaf development and sustain vegetative growth. Vegetative reproduction is facilitated by fragmentation of the plant body followed by regeneration from any small part bearing a bud.
Multiplication by means of modified stems such as rhizomes, stolons, and runners is widespread in temperate species. These specialized organs also serve the purpose of sustaining plants during adverse conditions. In hot climates vegetative growth may be more continuous. Vegetative parts that can grow into new plants may be transported by water or animals, further contributing to the distribution of a species.
There are many instances of pseudovivipary, wherein asexual reproductive units replace some or all of the normal sexual flowers in the inflorescence. This method is common in the family Alismataceae, in which the inflorescence may set seed above water but bear young plantlets when submerged.
In many genera there is an abbreviated axis from which arises the crown of leaves. This rootstock becomes swollen with starch grains and serves as a storage organ during the resting period when foliage dies down. Many plants with underground stems reproduce vegetatively and spread horizontally by means of runners at the soil-surface level or by similar underground stems. These become erect at intervals to form new plants with adventitious roots. Later, intermediate parts may disintegrate and the secondary plants become independent.
Species of Sagittaria remain alive during adverse seasons by the production of special terminal tubers behind the apical bud. These structures are two to five centimetres long and may be brightly coloured blue and yellow. They remain dormant during the winter but sprout into a new plant the following spring.
Many species of Potamogetonaceae produce turions, or winter buds, at the apex of erect stems and branches. These hardened terminal buds break off of the stem and fall to the substrate, where they lie dormant over the unfavourable conditions and germinate into a new plant during the next growing season.
Vegetative reproduction is of the utmost importance in the maintenance and spread of some species. In all three families of the order Alismatales it is correlated with aquatic existence, and this perhaps accounts for its success and frequency in comparison with sexual reproduction, which is not adapted to aquatic conditions.
Apparently little or no vegetative reproduction takes place in the Triuridales. The majority of the life history of Triuridales is spent underground; the plant emerges only when conditions are favourable for flowering and fruiting.
