Flowering and Seed Production across the Lemnaceae

Abstract

Plants in the family Lemnaceae are aquatic monocots and the smallest, simplest, and fastest growing angiosperms. Their small size, the smallest family member is 0.5 mm and the largest is 2.0 cm, as well as their diverse morphologies make these plants ideal for laboratory studies. Their rapid growth rate is partially due to the family’s neotenous lifestyle, where instead of maturing and producing flowers, the plants remain in a juvenile state and continuously bud asexually. Maturation and flowering in the wild are rare in most family members. To promote further research on these unique plants, we have optimized laboratory flowering protocols for 3 of the 5 genera: Spirodela; Lemna; and Wolffia in the Lemnaceae. Duckweeds were widely used in the past for research on flowering, hormone and amino acid biosynthesis, the photosynthetic apparatus, and phytoremediation due to their aqueous lifestyle and ease of aseptic culture. There is a recent renaissance in interest in growing these plants as non-lignified biomass sources for fuel production, and as a resource-efficient complete protein source. The genome sequences of several Lemnaceae family members have become available, providing a foundation for genetic improvement of these plants as crops. The protocols for maximizing flowering described herein are based on screens testing daylength, a variety of media, supplementation with salicylic acid or ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid) (EDDHA), as well as various culture vessels for effects on flowering of verified Lemnaceae strains available from the Rutgers Duckweed Stock Cooperative.

Characterization of Frond and Flower Development and Identification of FT and FD Genes From Duckweed Lemna aequinoctialis Nd

“…Protandry is thought to reduce self-pollination, thereby contributing to the genetic diversity of a species (Lloyd and Webb, 1986). Examples of protandry and protogyny (the female phase proceeds the male phase) occur in Lemnoideae plants (Fourounjian et al, 2021). Our observations suggested that L. aequinoctialis develops two stamens, one of which grows longer; the longer stamen becomes exposed outside the frond, but, in our culture conditions, the shorter stamen often was not displayed (Figures 2E-H).…”

“…The timing of stamen and pistil maturation differs among species in the Lemnoideae. Stamen maturation proceeds pistil maturation in some Lemnoideae plants, whereas the opposite timing occurs in others (Fourounjian et al, 2021). In L. aequinoctialis, stamens appear first (Figure 2E), then pistils appear (Figure 2F).…”

New Insights into Interspecific Hybridization in Lemna L. Sect. Lemna (Lemnaceae Martinov)

“…We tried to verify if the hybrid clones that we have identified could correspond to putative 'L. symmeter' on these criteria, by inducing flowering through treatment with salicylic acid (SA) as reported by others [33,34]. After four weeks of cultivation in 20 µM SA, we were able to induce flowering in two out of three L. gibba clones (7742a and 9598, not 8124), but neither the six hybrid clones, nor two L. minor clones (9977 and 9942) showed reproductive organs after six weeks.…”

The World Smallest Plants (Wolffia Sp.) as Potential Species for Bioregenerative Life Support Systems in Space

“…Flowers are composed of one stamen with the anther and a pistil within which there is one atropous ovule [13]. Recently, laboratory protocols were developed to control flowering in W. microscopica [33]. Nevertheless, several aspects of the reproductive biology and ecology of Wolffia species are still unexplored.…”