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Quercus acutissima subsp. kingii
Quercus acutissima Carruth. is a species whose natural distribution covers a vast territory in East and Southeast Asia, from central Nepal...

Seed Desiccation in Quercus floribunda

Seedlings of Quercus floribunda

Seeds of Quercus floribunda germinated under laboratory conditions 

Based on their desiccation response, seeds are divided into two broad categories: orthodox and recalcitrant. While the majority of temperate tree seeds are orthodox, a few species possess recalcitrant seeds, which remain sensitive to water loss. Quercus is a common temperate forest tree genus that produces recalcitrant seeds and is well reported to lose its viability when moisture content decreases. The rate of seed water loss in this species depends on the existing environmental conditions.

Among known species of oaks in Indian Western Himalaya, Quercus floribunda requires a synchronization of seed fall with the commencement of the rainy season, due to the short duration of seed viability. A delay in the monsoon can thus drastically reduce the percentage of seed germination as the seeds are vulnerable to desiccation (Rao 1984). This vulnerability calls for urgent attention to be given to understanding the role of seed desiccation sensitivity in natural regeneration and the subsequent change in composition of forests under changing climate. Singh and Singh (1987) have shown that seed germination in Q. floribunda is sensitive to desiccation. The response breadth used to express seed germination response to different environmental factors was found to be very narrow on seed desiccation gradient (B = 0.535). Due to the prevalence of such seeds within Quercus, this genus has attracted interest in relation to understanding recalcitrant seed storage behavior. I conducted studies under the supervision of Dr. Ranbeer S. Rawal in the laboratory and an experimental nursery to understand seed germination behavior in relation to desiccation for different drying periods in Q. floribunda. Based on the results we recommend that the seeds of Q. floribunda should be sown within 7 days, when the seed moisture content remains above the critical level of 34%. These results have implications in forestry practice, conservation, and management for coping with the practical problems of storing Q. floribunda seeds.

Description

Major attributes

Description

Common English name

Green oak

Local name

Moru/Tilonj

Habit

Large evergreen tree

Stem

Bark dark grey or dark reddish-brown, rough with shallow cracks, exfoliating in irregular woody scales. Young shoots and petioles with floccose stellate pubescence.

Leaves

Leaves usually 2-4 × 1-2 inches, oblong-lanceolate or elliptic, entire or cuspidate-serrate especially on young tree, acute, mucronate, coriaceous, rather dark shining green and glabrous on both sides; lateral nerves 8-12 pairs, mostly forked. Petiole 1-3 inch long. Male catkins 2-3 inches long, much interrupted.

Flowering

Female flowers in short axillary spikes (April-May)

Seed maturation time

August

Acorns

Acorns about 1 inch long, ovoid, one-third immersed in the cupule.

Seed Coat

Hard

 
Ecology

The species is native to Afghanistan, Bangladesh, India, Nepal, and Pakistan. It occurs throughout the Western Himalaya at altitudes between 2,000 and 2,400 m. It is a thermo-phobic species growing best on northern aspects and forming a transition zone between Q. leucotrichophora forests at lower altitude and Q. semecarpifolia forests at higher altitude in Kumaun, Western Himalaya. It is abundant and usually gregarious, preferring deep soils and growing frequently on limestone. Although found on all the aspects, it avoids very dry situations and favors moist, cool localities and northern aspects. The common associates of this species are Abies pindrow, Cedrus deodara, Lyonia ovalifolia, Rhododendron arboreum, Viburnum cotinifolium, and Pyrus pashia.

Acknowledgments

I would like to thank Dr. Ranbeer S. Rawal for his contribution to this study.

Photos © Meenakshi Negi

References

Rao, P.B. 1984. Regeneration of some trees of Western Kumaun Himalaya. PhD thesis, Kumaun University, Nainital, India.

Singh, J.S. and S.P. Singh. 1987. Forest vegetation of Himalaya. Botanical Review 53: 80-192.