Measurement of oxygen tension changes in the style during pollen tube growth

Abstract

Using a Clark micro electrode the actual oxygen tension at various places in a style can be measured. Within the unpollinated, ripe style of Hippeastrum a pO2 gradient occurs. In the upper part, possibly with a little increase in the stigmatic branches, a very high oxygen tension is found; in the lower part, about 5 mm from the ovary, a sudden decrease occurs. In the ovary itself the oxygen tension is extremely low. After pollination, passage of the mass of pollen tube tips can be followed by a fairly sharp drop of the oxygen tension, which shifts down the style with progressive growth. This oxygen tension depression seems to be sharply limited to the region of pollen tube tips and the amount of decrease is dependent on the growth rate of the tubes. After passage of the pollen the original high level of oxygen tension is not fully restored in the upper style. This suggests that the metabolic activity of the pollen tube is strongly linked with the metabolic condition in the style. It seems that tubes grow most of their way to the egg under aerobic conditions; only at the base of the style, just before entering into the ovary, does the pollen have to switch over to an anaerobic pathway. For most of the style oxygen tension does not form a tropic gradient for tube growth.

Pyruvate Decarboxylase Provides Growing Pollen Tubes with a Competitive Advantage in Petunia

“…This makes additional sense in light of the fact that oxygen tension in the style may be low (Linskens and Schrauwen, 1966). However, to our knowledge, adh mutations have never been reported to affect male gametophyte function.…”

“…Such conditions might exist in the style during in vivo pollen tube growth (Linskens and Schrauwen, 1966;Blasiak et al, 2001). To examine the pollen tube growth rate under in vivo conditions, both types of pollen grains were germinated on the stigma of wild-type W115 plants, and the Pollen from wild-type, heterozygous pdc2/þ, and homozygous pdc2/ pdc2 plants were tested.…”

“…In vitro-grown tobacco pollen accumulated ethanol even at an oxygen concentration of 40%, and the flux to ethanol was regulated by the sugar concentration in the medium (Bucher et al, 1995;Tadege and Kuhlemeier, 1997). Oxygen levels in the style are likely to be reduced (Linskens and Schrauwen, 1966). It is not known how this limited oxygen availability affects the regulation of respiratory metabolism.…”

“…Oxygen pressure is high in the stigma and style but suddenly decreases at the base of the style, approaching zero values in the ovary. Moreover, pollen tube growth itself creates hypoxic regions within the style (Linskens and Schrauwen, 1966). Thus, energy metabolism may influence pollen tube growth both directly and, possibly, indirectly through the generation of guidance signals.…”

Dynamic Adaption of Metabolic Pathways during Germination and Growth of Lily Pollen Tubes after Inhibition of the Electron Transport Chain

“…However, the partial pressure of oxygen differs along the style tissue (Linskens and Schrauwen, 1966), and therefore, one might assume that tube growth rates may vary inside the style tissue due to changes in oxygen supply that affect the respiration rate. To maintain its high growth speed even in regions of lower partial pressure of oxygen, additional metabolic pathways for energy production may have to be active.…”