RESEARCH PAPER Studies of Pollen Characteristics in Plants of Fruitless Tecomella undulata (Sm.) Seem. (Bignoniaceae) in Golparaki Region of Jiroft City, Iran Farkhondeh Rezanejad 1 • Farzad Ganjalikhani Hakemi 1 Received: 1 November 2015 / Accepted: 25 March 2016 Ó Shiraz University 2017 Abstract Tecomella undulata is valued for beautiful flowers, resistance against extreme temperature and drought, stabilizing shifting sand dunes, medicinal prop- erties and wood production. In spite of massive flowering, the species is seedless. The present study examines the causes of its sterility indicating on pollen characteristics. Flowers were hand pollinated by pollen of either self- or outcross pollen. Some flowers were tagged as open polli- nation treatment. Pollen structure, in situ and in vitro pollen germination and pollen tube growth were analyzed. Mature pollen grains are heteromorphic, mostly heterogeneous sized as small and large. Both pollen grains types are prolate and tricolpate with rugulate–reticulate sculpture. Flowers are protandrous and have long stylus; a nectarif- erous tissue secreting abundant nectar exists in the ovary base. No effective pollinator visited flowers during the observation period. No pollen germination and pollen tube growth were observed in self- and cross-pollinated styles and under in vitro condition. It seems that pollen hetero- geneity, lack of pollinators and pollen limitation, the failure of autogamy due to protandry or long styli as well as self- incompatibility resulted in pollen sterility and seedlessness. In addition, probably polyploidy and cytomixis affect infertility too that needs to be studied in detail in the future. Keywords Pollen germination Á Pollen heterogeneity Á Pollination Á Protandry Á Tecomella undulate 1 Introduction Tecomella undulata belonging to family Bignoniaceae is commonly called as Golparaki in Persian. Species of Bignoniaceae are mainly distributed through tropical rain forests and dry areas (Fischer et al. 2004), representing the second most diverse family of wood plants in seasonal dry forests (Gentry 1988). This monotypic and ornamental plant is one of the important ornamental shrubs/trees of the arid regions in Iran, Arabia, southern Pakistan and north- west India up to an elevation of 1200 m (Shankaranarayan and Nanda 1963; Aghdaei et al. 2012). The species has been identified as important for environmental conserva- tion in arid zones as a windbreak and stabilizer shifting sand dunes; it acts as a soil binder by spreading of a net- work of lateral roots on the top of the soil (Kumawat et al. 2012; Tyagi and Tomar 2013). It is also a very useful species for landscaping and afforestation of the drier tracts due to its higher survival rates even in water and nutrient poor soils of arid areas (Joshi et al. 1977), and extreme drought conditions (Shankaranarayan and Nanda 1963; Bhau et al 2007). T. undulata is highly valuable in terms of economy for its quality wood and medicinal properties (Bhandari 1990; Ahmad et al. 1994). Rao et al. (1989) noticed a significant increase in carbon, nitrogen and abundant growth of different microorganisms in the rhi- zosphere by T. undulate. Thus, it is highly mycorrhizal in natural habitat and can be selected for research, including the ‘biofertilizer’ aspect in arid zones (Rao et al. 1989; Bhau et al. 2007). United Nations Environment Pro- grammes (UNEP), World Conservation Monitoring Centre (WCMC) Nairobi, Kenya, has included T. undulata into ‘‘Category 1-Indeterminate’’ of their list of threatened plants to emphasize the status of T. undulata and the urgent need for conservation (Kumar et al. 2008). & Farkhondeh Rezanejad frezanejad@uk.ac.ir 1 Department of Biology, Shahid Bahonar University of Kerman, Kerman, Iran 123 Iran J Sci Technol Trans Sci DOI 10.1007/s40995-017-0338-2