Pollination Biology and Breeding System of Maple Species Acer oblongum Wall. ex DC. (Sapindaceae) Showing Mixed Syndromes of Wind and Insect Pollination


Acer oblongum is unique among maples because of the leaf structure and cryptic monoecy. In the present study, an in-depth investigation of reproductive biology has been carried out to study the pollination biology and breeding system of the tree species. The flowers show mixed characteristics of both entomophilous and anemophilous pollination in structure and pollen characteristics, respectively, and can thus be considered as ambophilous (exhibiting traits conducive to both insect and wind pollination). The wind was the primary means of pollination, but exclusion experiments showed that insects (Apis dorsata and syrphid fly) also facilitated pollination by 3–5%. The stigma of hermaphrodite flowers is located 2–3 cm above the level of indehiscent anthers. Interestingly, the insect pollinators hardly came in contact with the pistil; they only brought the pollen close to the stigma and shed it in its vicinity, to be trapped almost like the wind-borne pollen grains on the stigmatic papillae. Anthers of hermaphrodite flowers serve a relict function by attracting insect pollinators, but not contributing to self or cross-pollination. Fruit set following manual geitonogamous and xenogamous pollination showed a difference. The probable reason accounting for low fruit set seems to be the limited number of pollen donors (Staminate type II flowers), high pollen sterility, sparse distribution of individual trees, and geitonogamous pollen. Fruits are dry, indehiscent samaras. Mature fruits do not invariably bear seeds inside since hollow fruits are formed even when ovules inside remain unfertilized.

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The research was supported by the Ministry of Environment, Forest and Climate Change, New Delhi, as part of “All India Coordinated Research Project on Reproductive Biology of RET Tree Species” (No. 22/2/2010-RE) sanctioned to AK Bhatnagar, and by the Research and Development Grant from the University of Delhi to AK Pandey. Thanks are also due to Shri S.K. Dass for help in the preparation of photographic plates.

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Correspondence to Arun K. Pandey.

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Significance Statement

Acer oblongum is a threatened Himalayan tree species that is valued for its timber. The species is vanishing from its natural habitats due to anthropogenic activities and also due to a low regeneration rate. To know the reasons for poor regeneration in nature, it is important to study the reproductive biology of the species. This type of study is a prerequisite in developing a species-specific conservation programme.

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Yadav, N., Pandey, A.K. & Bhatnagar, A.K. Pollination Biology and Breeding System of Maple Species Acer oblongum Wall. ex DC. (Sapindaceae) Showing Mixed Syndromes of Wind and Insect Pollination. Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci. 90, 489–500 (2020). https://doi.org/10.1007/s40011-019-01120-x

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  • Acer oblongum
  • Cryptic monoecy
  • Ambophilous
  • Geitonogamy
  • Pollen sterility
  • Stigmatic papillae
  • Xenogamy