Schwallier Rachel, van Wely Valeri, Baak Mirna, Vos Rutger, van Heuven Bertie Joan, Smets Erik, van Vugt Rogier R, Gravendeel Barbara
Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands.
Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK Leiden, The Netherlands.
Plants (Basel). 2020 Nov 18;9(11):1603. doi: 10.3390/plants9111603.
An enigmatic feature of tropical pitcher plants belonging to the genus is their dimorphic prey-capturing pitfall traps. In many species, the conspicuously shaped upper and lower pitchers grow from a swollen leaf tendril tip until finally opening as insect-alluring devices. Few have studied the ontogeny of these traps from an anatomical and quantitative morphological perspective. We investigated whether the anatomy and development of lower and upper type pitchers of differ or overlap in terms of 3D geometric morphology and microstructure progression and presence. We hypothesized that there is an overlap in the initial, but not all, developmental stages of the two pitcher types and that one pitcher type is suspended in development. We identified four important morphological changes of pitcher ontogeny and defined these as curvation, elongation, inflation and maturation phases. Pitcher length indicated progress through developmental phases, and we propose to use it as a tool for indication of developmental stage. Microstructure development coincided with the developmental phases defined. Additionally, we discovered a new anatomical feature of extrafloral nectariferous peristomal glands between the inner peristome ridges of upper and lower pitchers being hollow and analyze the chemistry of the sugars on the outside of these glands. Ontogenetic shape analysis indicated that upper and lower pitcher types develop with similar phase progression but have no directly overlapping morphology. This means that upper pitchers are not a derived state from lower pitchers. Independent developmental programs evolved to produce distinctly shaped upper and lower pitchers in likely to exploit different food sources.
猪笼草属热带猪笼草的一个神秘特征是其具有两种形态的捕食陷阱。在许多物种中，形状显著不同的上位笼和下位笼从肿胀的叶卷须尖端长出，最终作为吸引昆虫的装置开放。很少有人从解剖学和定量形态学的角度研究这些陷阱的个体发育。我们研究了猪笼草属下位笼和上位笼在三维几何形态、微观结构进展及存在情况方面的解剖结构和发育是否存在差异或重叠。我们假设这两种笼类型在最初的但并非所有的发育阶段存在重叠，并且其中一种笼类型在发育过程中暂停。我们确定了猪笼草个体发育的四个重要形态变化，并将其定义为弯曲、伸长、膨胀和成熟阶段。笼的长度表明了发育阶段的进展，我们建议将其用作指示发育阶段的工具。微观结构的发育与所定义的发育阶段一致。此外，我们发现了上位笼和下位笼内唇脊之间的花外泌蜜口缘腺体的一个新解剖特征，即这些腺体是中空的，并分析了这些腺体外部糖分的化学组成。个体发育形状分析表明，上位笼和下位笼类型以相似的阶段进展发育，但没有直接重叠的形态。这意味着上位笼不是从下位笼衍生而来的状态。独立的发育程序进化产生了猪笼草属中形状明显不同的上位笼和下位笼，可能是为了利用不同的食物来源。
