**Preface**

In this artfully curated Special Issue of *Plants*, we unfold the intricate tapestry of plant morphology, a field where the architecture of life meets the rigor of mathematics. The subject at hand delves into the profound relationship between the structural features of plants and their adeptness at navigating the environmental labyrinth, revealing a fascinating narrative of survival and adaptability.

The scope of our inquiry extends beyond the mere contours of leaves and branches, touching upon the very essence of botanical function. The symmetrical ballet of plant shapes—leaves, fruits, seeds, roots, and trunks—choreographs a story of life that, while seemingly aligned with geometric perfection, dances vivaciously with variability. Even within the same species, the stage of development dresses plants in a wardrobe of different morphological characteristics.

Our aim is to quantify these characteristics with mathematical elegance, utilizing geometric and statistical models as our compass. This pursuit is not solely academic; it seeks to arm botanists, ecologists, and mathematicians with the tools to interpret the evolutionary and developmental narrative of flora. The purpose, deeply rooted in scientific curiosity, is to enhance our collective understanding of plant strategies for thriving in a dynamic world.

The authors, a coalition of minds from diverse disciplines, have convened in these pages, offering their insights like seeds hoping to germinate new avenues of thought. Their work is an ode to the unity of natural forms, inspired by the universal geometric equation proposed a decade ago by Dr. Johan Gielis.

To our discerning audience—researchers and enthusiasts alike—this Special Issue addresses you in the spirit of exploration and understanding. As editors, we extend our deepest gratitude to those who have watered the seeds of this endeavor with their support, wisdom, and critique. Together, we stand at the cusp of a deeper comprehension of the green mysteries that cloak our planet, poised to reveal the hidden rhymes and reasons of plant form and function.

> **Jie Gao, Weiwei Huang, Johan Gielis, and Peijian Shi** *Editors*

**Jie Gao 1,\*, Weiwei Huang <sup>2</sup> , Johan Gielis <sup>3</sup> and Peijian Shi <sup>2</sup>**


Functional plant traits include a plant's phenotypic morphology, nutrient element characteristics, and physiological and biochemical features, reflecting the survival strategies of plants in response to environmental changes. In this special issue, we aim to uncover the environmental adaptation mechanisms of plant functionality by studying the morphology and functions of plant organs including leaves, fruits, and seeds, providing a theoretical basis to understand the impact of global changes on plant growth and development.

Different species of *Silene* seeds with distinct morphologies exhibit varying harmonic numbers when analyzed using the elliptical Fourier transform (EFT) model [1]. Smoother seeds have fewer harmonic numbers, while wrinkled, spiky, and papillate seeds require more harmonic numbers. The Gielis equation and the modified Brière equation have shown remarkable validities in describing plant leaf morphology [2–4]. The morphological characteristics of bamboo leaves are closely related to canopy management practices [5], and different canopy management practices result in significant differences in leaf morphology and the trade-off relationships among various functional traits.

Environmental factors play a crucial role in shaping plant functional traits. Climate factors, such as temperature and precipitation, significantly influence the temporal variation in nutrient elements of leaf litter in the Ailao Mountains of China, effectively improving nutrient utilization efficiency and shortening turnover cycles [6]. Leaf nutrient content in forests is mainly influenced by soil nutrients and climate factors [7,8]. Different ecosystems also exhibit significant differences in soil nutrient content, with forest soil having higher total nitrogen content than grassland soil, while the carbon-to-nitrogen ratio in forest soil is lower than in grassland soil [9]. Controlled factors for functional leaf traits vary with geographic locations. Leaf area, carbon-to-nitrogen ratio, carbon-to-phosphorus ratio, nitrogen-to-phosphorus ratio, phosphorus content, and nitrogen isotope content in Chinese forests show significant correlations with latitude and longitude. Leaf characteristics in the southern regions are mainly influenced by climatic factors, while those in the northern regions are primarily affected by soil factors [10]. Additionally, varying degrees of light exposure also play a significant role in plant functional traits [11]. Apart from environmental factors, plant hormones also have a significant impact on plant functional traits. Exogenous sucrose and gibberellin significantly increase the internode length and total internode number of bamboo, significantly contributing to increased plant height. Gibberellin more significantly affects internode length, while sucrose increases the total internode number [12]. In addition, functional leaf traits can differ significantly between hybrid plants and their parents [13]. Functional plant traits play an essential role in exploring vegetation productivity and mitigating air pollution. Urban green spaces composed of various functional trait plants help to reduce air pollution levels [14] and serve as an important factor affecting urban ecosystem productivity [15,16].

**Citation:** Gao, J.; Huang, W.; Gielis, J.; Shi, P. Plant Morphology and Function, Geometric Morphometrics, and Modelling: Decoding the Mathematical Secrets of Plants. *Plants* **2023**, *12*, 3724. https://doi.org/ 10.3390/plants12213724

Received: 19 October 2023 Accepted: 23 October 2023 Published: 30 October 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

<sup>1</sup> College of Life Sciences, Xinjiang Normal University, Urumqi 830054, China

**Author Contributions:** J.G. (Jie Gao): conceptualization, methodology, and investigation. J.G. (Jie Gao), W.H., J.G. (Johan Gielis) and P.S.: formal analysis. J.G. (Jie Gao): writing—original draft. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region (No. 2022D01A213), Fundamental Research Funds for Universities in Xinjiang (No. XJEDU2023P071), Innovation and Entrepreneurship Training Program for College Students in 2023 (No. S202310762004), Xinjiang Normal University Landmark Achievements Cultivation Project (No. XJNUBS2301), Xinjiang Graduate Innovation and Entrepreneurship Project and Tianchi Talent Program.

**Conflicts of Interest:** The authors declare no conflict of interest.

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