Analysis on Leaf Anatomy of 7 Begonia Species and Evaluation on Their Heat Tolerance

Abstract

【Objective】Begonia often referred to as the "king" of ornamental plant. In the study, we explored the relationship between the leaf structure and heat among Begonia species with diverse leaf colors, aiming to screen out Begonia species with high ornamental value and strong heat tolerance.【Method】The leaf anatomies of seven Begonia species were observed by using paraffin sectioning. Cluster analysis and correlation analysis were utilized to identify indicators related to leaf tissue structures. Additionally, a membership function method was implemented to comprehensively evaluate the heat tolerance of the seven Begonia species.【Result】(1) The leaves of all seven species were heterophyllous with both upper and lower epidermis being composed of a tightly arranged single layer of cells. The upper epidermis was flat or convex, while stomata concentrated on the lower epidermis. The mesophyll was differentiated into palisade and spongy tissues. The palisade tissue was underdeveloped, usually consisting of 1 to 2 layers of chloroplast-rich cells. In contrast, the spongy tissue was more developed, with 3 to 5 layers. Leaf colors varied between species and were associated with differences in palisade cell morphology and arrangement. (2)Total leaf thickness, spongy tissue thickness, palisade-to-spongy tissue ratio, and tissue tightness were key anatomical factors influencing heat tolerance. (3)The heat tolerance ranking from highest to lowest were as: B. barsalouxiae, B. luzhaiensis, B. luochengensis, Begonia sp., B. debaoensis, B. variifolia, and B. handelii. According to this ranking, we categorized them into three levels of tolerance: B. barsalouxiae as heat-tolerant, B. luzhaiensis and B. luochengensis as moderately heat-tolerant, and B. debaoensis, B. variifolia, and B. handelii and Begonia sp. as low heat-tolerant.【Conclusion】Observations of leaf anatomy revealed that the palisade tissue was underdeveloped in several Begonia species. In contrast, the spongy tissue was more developed, resulting in a quite loose leaf structure, and this loose structure greatly influenced heat tolerance in Begonia.

Keywords

• begonia
• leaf
• anatomy
• heat tolerance
• membership function method
• correlation analysis