Coordination of leaf economics traits within the family of the world’s fastest growing plants (Lemnaceae)

The duckweed family (Lemnaceae) is a group of free-floating aquatic plants
with bodies consisting of single floating fronds that multiply clonally.
Although they are known to have the fastest relative growth rate (RGR)
among higher plants, their functional trait coordination in relation to
within-family variation of RGR is poorly understood. We tested how
duckweed species fit within the trait covariation patterns known as the
worldwide leaf economics spectrum (LES). To this end, several functional
traits were evaluated for 15 duckweed species, and their covariation
patterns were compared with those in the global database of plant
functional traits. As a group, duckweeds exhibited the most acquisitive
suite of traits, with extremely small leaf mass per area (LMA), short
lifespan, and high mass-based photosynthetic rate (Amass). These LES
traits showed a tight correlation with RGR, corroborating our hypothesis
that acquisitive leaf resource economics underpins their extremely high
RGR. However, unlike other higher plants, LMA showed weak association with
leaf lifespan and Amass within duckweed family. We also found a unique
positive correlation between duckweed LMA and area-based photosynthetic
rates, an indication that their LMA represents different functional
significance compared to typical higher plants. Synthesis. Duckweeds, the
world’s fastest-growing plants, mostly follow the worldwide LES and locate
at its extreme end. The slight deviation from the LES highlights that
duckweeds experience some physical and chemical constraints not faced by
other higher plants.