A histological study of Rafflesia patma revealed the simplicity of a flower’s vascular tissue and epidermal features of flower organs, including their structures and pigmentation. Rafflesia is an endophytic holoparasitic plant that infects Tetrastigma. In a previous study, we characterized the shape of the strands of an endophyte (Rafflesia patma Blume) and hypothesized their distribution. In this study, we deepened our analysis by assessing parts of flower tissue sampled during anthesis, performed surface casting of the abaxial and adaxial sides of the perigone lobe to profile their surface features, and histologically characterized the perigone lobe, perigone tube, and central column base, including the anther and cupula region. The objective of these observations was to compare tissues from different organs and the distribution of cells staining positive for tannin, suberin, and lignin. Observable features in this study were vascular and epidermal tissue. We also observed reduced vascular tissue with xylem and vascular parenchyma in multiple organs. The adaxial epidermis found in the perigone lobes and tube had papillate cells, and their function might be to assist with the emission of odor through chemical evaporation. The abaxial epidermis, also found in perigone lobes and tube, had flattened cells. These, combined with the nearby flattened parenchyma cells, especially in the outermost, early perigone lobe, might provide a tougher (stiffer) outer protective barrier for the flower. The accumulation of tannin in perigone lobes might offer protection to the flower from herbivores prior to anthesis. Although a previous observation indicated the possibility of stomata on the surface of Rafflesia flowers, no stomata were found in this study.

中文翻译：

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Rafflesia patma Blume 花器官：表皮和血管结构的组织学，以及气孔的寻找

Rafflesia patma 的组织学研究揭示了花的维管组织和花器官的表皮特征的简单性，包括它们的结构和色素沉着。大王花是一种内生的全寄生植物，会感染四柱花。在之前的一项研究中，我们描述了内生菌 (Rafflesia patma Blume) 链的形状并假设了它们的分布。在这项研究中，我们通过评估开花期间采集的部分花组织来加深我们的分析，对 perigone 裂片的背面和正面进行表面铸造以描绘它们的表面特征，并在组织学上表征 perigone 裂片、perigone 管和中央柱基部，包括花药和圆顶区。这些观察的目的是比较来自不同器官的组织以及单宁、木栓质和木质素染色呈阳性的细胞分布。本研究中可观察到的特征是血管和表皮组织。我们还观察到多个器官中具有木质部和血管实质的血管组织减少。在周边叶和管中发现的近轴表皮有乳头状细胞，它们的功能可能是通过化学蒸发帮助散发气味。背轴表皮，也发现在周边裂片和管中，有扁平的细胞。这些，再加上附近扁平的薄壁组织细胞，特别是在最外层的早期周缘叶中，可能会为花朵提供更坚韧（更硬）的外部保护屏障。单宁在花期裂片中的积累可能会在开花前保护花朵免受食草动物的侵害。尽管先前的观察表明大王花表面可能存在气孔，但本研究未发现气孔。