Inspecting the differences in mechanical resistance between flowers and leaves by multiple mechanical testing and calibration methods

Abstract Background and Aims Flower petal integrity affects the success of plant reproduction and ecological adaptability. The mechanical resistance of plant organs indicates their capacity to withstand physical damage and preserve structural integrity. However, little is known about the mechanical resistance of flowers and their differences from leaves. Methods To address the aforementioned research gaps, we quantified flower petals from 43 species and leaves from 86 species, employing two forces that characterize mechanical resistance: force to punch and force to tear. For force to punch, three different diameter punch needles were used to measure and three methods were employed for calibration. Additionally, we measured functional traits of petals and leaves. Key Results We found that petals have significantly lower mechanical strength than leaves in both punch and tear forces. The force to punch and force to tear of petals and leaves were positively correlated with tissue thickness, cuticle thickness and dry mass per unit area. The vein density of petals was positively correlated with force to punch and force to tear, while force to tear was negatively correlated with floral tissue density after phylogenetic independent contrast correlation analysis. For reticular venation leaf, the vein density had no significant relationship with force to tear, but was positively correlated with tissue density. Conclusions Our results indicated that there were differences in the structural basis of mechanical resistance between flowers and leaves. Regarding the most classical mechanical testing method, force to punch, different needle diameters and calibration methods can affect the results for both the petal and leaf. Our research results provide an important reference for better understanding the ecological adaptability of flowers.