Oecologia

, Volume 95, Issue 2, pp 194–201

Photosynthetic characteristics of a giant alpine plant, Rheum nobile Hook. f. et Thoms. and of some other alpine species measured at 4300 m, in the Eastern Himalaya, Nepal

  • Ichiro Terashima
  • Takehiro Masuzawa
  • Hideaki Ohba
Original Papers

DOI: 10.1007/BF00323490

Cite this article as:
Terashima, I., Masuzawa, T. & Ohba, H. Oecologia (1993) 95: 194. doi:10.1007/BF00323490

Abstract

The photosynthetic characteristics of a giant alpine plant, Rheum nobile Hook. f. et Thoms. and of some other alpine species were studied in situ at 4300 m, in the Eastern Himalaya, Nepal, during the summer monsoon season. Although rainy and overcast weather was predominant, the daytime photon flux density (400–700 nm) ranged from 300 to 500 μmol quanta m-2 s-1. Under such conditions, the temperature of leaves of R. nobile ranged from 10 to 14°C, and the rate of photosynthetic CO2 exchange ranged from 10 to 16 μmol CO2 m-2 s-1. The ratios of the maximum rate of photosynthetic CO2 fixation to leaf nitrogen content (defined as instantaneous nitrogen-use efficiency, NUE) for the Himalayan forbs that were examined in situ were similar to the NUE values reported for lowland herbaceous species examined under lowland conditions. In contrast to the common belief, theoretical calculations indicate that the decrease in the rate of photosynthesis due to low atmospheric pressure is small. These Himalayan forbs appeared to overcome this small disadvantage by increasing stomatal conductance. Suppression of photosynthesis caused by blockage of stomata by raindrops appeared to be avoided by either of two mechanisms: plants had large hypostomatous leaves that expanded horizontally or they had obliquely oriented amphistomatous leaves without bundle sheath extensions. All these observations indicate that the gas-exchange characteristics of alpine forbs in the Eastern Himalaya are adapted to the local wet and humid monsoon conditions and thus photosynthetic rates attained during the monsoon period are similar to those of lowland plants.

Key words

Alpine plantsHimalayaMonsoonNitrogenPhotosynthesis

Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Ichiro Terashima
    • 1
  • Takehiro Masuzawa
    • 2
  • Hideaki Ohba
    • 3
  1. 1.Department of Botany, Faculty of ScienceUniversity of TokyoTokyoJapan
  2. 2.Department of Biology, Faculty of ScienceShizuoka UniversityShizuokaJapan
  3. 3.University MuseumUniversity of TokyoTokyoJapan