Endemic Papilionoideae of the Caatinga: a contribution to the palynological knowledge of Leguminosae

ABSTRACT Papilionoideae is the most diverse subfamily of Leguminosae, representing approximately 39 % of its species. Although it is particularly species rich and diverse in the Caatinga, the main phytophysiognomy of the semiarid Northeast Region of Brazil, little is known about the pollen morphology of the species that occur there. This study analyzes and describes the pollen morphology of the 27 species of Papilionoideae endemic to the Caatinga. Pollen grains were acetolyzed, mounted on permanent slides, measured, described and photomicrographed using light and scanning electron microscopy (LM and SEM, respectively). The main variable morphological features were pollen grain size, shape, amb, apertural type and exine ornamentation under LM (microreticulate, reticulate, psilate or finely scabrate) and SEM (microreticulate, reticulate, rugulate, granulate, fossulate and perforate). High intergeneric morphological heterogeneity was observed while morphological variation within each genus was subtle. Nonetheless, size, endoaperture shape, fastigium presence/absence and exine ornamentation were found to be important characteristics for the identification of some species.

摘要：蝶形花亚科（Papilionoideae）是豆科（Leguminosae）物种多样性最高的亚科，其物种数约占豆科总物种数的39%。尽管该亚科在巴西东北部半干旱地区的优势植被型——卡廷加植被（Caatinga）中物种极为丰富多样，但目前对该区域内分布的蝶形花亚科物种的花粉形态研究仍较为匮乏。本研究针对卡廷加植被特有的27种蝶形花亚科植物的花粉形态开展分析与描述。研究采用光学显微镜（LM）与扫描电子显微镜（SEM），对经醋酸酐分解处理并制作成永久玻片的花粉粒进行测量、描述及显微摄影。本研究重点观测的可变形态特征包括花粉粒大小、形状、轮廓、萌发孔类型，以及光学显微镜下的外壁纹饰（细网状、网状、光滑或细糙状）和扫描电子显微镜下的外壁纹饰（细网状、网状、皱块状、颗粒状、穴状及穿孔状）。研究结果显示，属间形态异质性较高，但同一属内的形态变异并不显著。尽管如此，花粉粒大小、内萌发孔形状、尖突结构的有无以及外壁纹饰，仍是部分该亚科物种鉴定的关键形态特征。