Bracts and basal leaves in Hacquetia epipactis differ in their spectral signatures

Abstract

Hacquetia epipactis is an understorey species that develops leaves, flowers, and fruits before the canopy layer closes. Its umbels are supported by green bracts. We examined the functional traits of these bracts and basal leaves for specimens, sampled at two altitudes. In this view, their specific leaf/bract area, biochemical, and optical properties were analysed over the course of their development in order to detect differences and changes in both structures. For lowland specimens, specific bract area decreased with age. An increase in UV-absorbing compounds over time was found for both locations. These were negatively related to reflectance in the UV range for basal leaves, whereas for bracts UV reflectance increased with age. We observed an increase in photosynthetic pigment contents during the development of bracts/basal leaves, which resulted in increased absorbance of photosynthetically active radiation for specimens from both altitudes. Detrended correspondence analysis plot based on the reflectance of bracts/basal leaves showed clustering of samples from different age classes with no respect to location. Redundancy analysis revealed high importance of bract/basal leaf biochemistry in explaining reflectance. UV-B-and UV-Aabsorbing compounds explained 13% and 8% each, carotenoids 9%, while anthocyanins and chlorophylls explained additional 4% of the reflectance spectra variability. Bracts and basal leaves displayed similar contents of photosynthetic pigments, which indicates their important photosynthetic function for both structures. The development of bracts/basal leaves showed greater influence on the examined parameters in comparison to altitude.

Comparative Study of Temporal Changes in Pigments and Optical Properties in Sepals of Helleborus odorus and H. niger from Prebloom to Seed Production

“…The development of flowers before leaf unfolding depends on carbohydrates accumulated in the underground organs [ 1 ]. In addition, some of the plant species have evergreen leaves [ 5 ], while others have green organs other than leaves, such as bracts and sepals [ 6 ]. These green structures contribute significantly to the plant energy budget [ 7 , 8 ], since they harvest solar energy in the early season, before canopy leaves unfold [ 6 ].…”

“…In addition, some of the plant species have evergreen leaves [ 5 ], while others have green organs other than leaves, such as bracts and sepals [ 6 ]. These green structures contribute significantly to the plant energy budget [ 7 , 8 ], since they harvest solar energy in the early season, before canopy leaves unfold [ 6 ]. Understorey plant species also respond to changing light conditions [ 9 ] by developing traits that adjust their light-use efficiency [ 2 , 10 ].…”