a3_gesamt
Pollen tube growth and pistil receptivity of high mountain plants under extreme climatic conditions

Flower longevity. At corolla opening, the flower enters the functional phase which in hermaphroditic flowers comprises the male phase (pollen dissemination) and the female phase (pollen deposition on the stigma and fertilization). The length of time a flower is functional may be an important determinant of male and female reproductive success. Several studies have shown that flower longevity generally increases with altitude. Within a plant species, however, flower longevity is plastic and not a fixed trait. It may be extended or shortened in response to short-term environmental variations. In representative plant species from the alpine and nival zone we tested the actual flower longevity under natural pollination and the potential flower longevity, i.e. the capacity to prolong flower functions (corolla life-time; duration of stigma, style and ovule receptivity) in the case when pollinators are absent or rare.
Among the female functions, stigma receptivity could be maintained longest (up to 29 d after onset of anthesis in R. glacialis). Ovule receptivity mostly ceased between 16 and 20 d. However, corolla life-time was even less plastic and thus limiting in most species.

Progamic processes and temperature. Processes occurring during flowering are especially vulnerable to changes of environmental conditions including temperature. Functions as stigma receptivity, ovule longevity, pollen germination and pollen tube growth are bound to a certain temperature range beyond which they increasingly fail, and, as a consequence, fertilization and seed production are reduced or absent. Plants at higher elevations are exposed to strong variations of temperature. On clear summer days, flowers may warm up to 30°C, but may cool down to freezing temperatures during the night or during a cold spell even in summer. Therefore the question arises, what the optimal temperature range and the limits for reproductive functions during the progamic phase in high mountain plants are. This was investigated in representative plant species from the alpine and nival zone in the Austrian Alps in situ and in laboratory experiments at controlled temperatures. We could show that mountain plants show a wide optimum temperature range for progamic processes which is consistent with the high temporal variability as a result of large diurnal variations in site temperatures. Most progamic processes worked from near freezing temperatures up to 30°C.

Funding
FWF-project P 18398-B03 

Publications

  • STEINACHER G., WAGNER J. (2010): Flower longevity and duration of pistil receptivity in high mountain plants. Flora: 376-387.
  • STEINACHER G., WAGNER J.: Effect of temperature on the progamic phase in high- mountain plants. Plant Biology, 14: 295-305.
  • STEINACHER G., WAGNER J. (2013): The progamic phase in high-mountain plants: from pollination to fertilization in the cold.  Plants 2, 343-359.
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