Abstract:

Aims Plant functional traits refer to various characteristics of plant morphology, structure, physiology, etc., reflecting plant responses and adaptations to environmental change. Flowers, as the core organs of plant reproduction, possess functional traits that can reflect plant-pollinator interactions, pollinator selection, and carbon investment strategies during the reproductive processes. It has been shown that flowers are developed from leaves, but the differences between flower and leaf functional traits across species remain largely unknown. By systematically quantifying the functional traits of flowers and leaves, this study investigated the differences in structures and functions of these two types of plant organs.

Methods To reveal the differences in functional traits between flowers and leaves, we selected 24 species in South China National Botanical Garden, and measured their both flower and leaf morphological traits (i.e., size and thickness), structural traits (i.e., vein diameter and density, mass per area, and dry mass content), mechanical strength (i.e., force to tear, and force to punch), and physiological traits (i.e., longevity, respiration rate, transpiration rate, stomatal conductance, nitrogen content, and phosphorus content).

Important findings Significant differences were found in the functional traits and carbon investment strategies between flowers and leaves. Force to punch, force to tear, and dry mass content of flowers were 50.0%, 42.9% and 30.7% of leaves. Additionally, the transpiration rate and stomatal conductance of flowers were 73.9% and 84.6% of leaves. Flower size and mechanical strength significantly increased with flower vein diameter, while leaf size was significantly and positively correlated with primary leaf vein diameter. Leaf mechanical strength was significantly and positively correlated with leaf minor vein diameter. Moreover, flower longevity was significantly and negatively correlated with flower respiration rate, transpiration rate, and stomatal conductance, but non-significantly correlated with flower mechanical strength and mass per area. In contrast, leaf longevity was significantly and positively correlated with leaf respiration rate, mechanical strength, and mass per area. Our findings revealed the trade-offs in resource allocation between plant reproduction and growth, and provided data support for species protection in the National Botanical Gardens.

Key words: flower, leaf, morphological trait, structural trait, mechanical strength, physiological trait