© 2003 Heron Publishing—Victoria, Canada
Boron influences pollen germination and pollen tube growth in Picea meyeri
Qinli Wang (1), Longdou Lu (2), Xiaoqin Wu (1), Yiqin Li (3) and Jinxing Lin (1, 4)
1. Key Laboratory of Plant Photosynthesis and Molecular Environment Physiology, Institute of Botany, Chinese Academy of Sciences,
Beijing 100093, China / 2. College of Life Science, Henan Normal University, Xinxiang 453002, China / 3. Deparment of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China / 4. Author to whom correspondence should be addressed (linjx@ns.ibcas.ac.cn) / Received March 27, 2002; accepted September 13, 2002; published online March 3, 2003
Summary
To study the role of boron in pollen germination and pollen tube growth of Picea meyeri Rehd. et Wils., pollen grains were cultured in standard medium or boron-deficient medium. Effects of boron on the localization
of pectins and callose in the walls of pollen tubes were observed by laser scanning confocal microscopy after staining with
aniline blue or immunolabeling with antibodies JIM5 and JIM7. Changes in the structures of pectins and phenolics were investigated
by fourier transform infrared (FTIR) microspectroscopy. Pollen germination in boron-deficient medium ranged from 18 to 24%,
whereas pollen germination in standard medium reached 61%. Callose accumulated in the tip-regions of pollen tubes cultured
in boron-deficient medium, but not in standard medium. Immunolabeling with antibody JIM5 revealed that acidic pectin preferentially
accumulated in the tip regions of pollen tubes cultured in boron-deficient medium, whereas acidic pectin was weakly distributed
along the entire lengths of pollen tubes cultured in standard medium. Esterified pectin, detected by immunolabeling with antibody
JIM7, showed a similar distribution pattern in pollen tubes in both the boron-deficient and standard treatments. The FTIR
spectra indicated slight increases in contents of phenolics and carboxylic acids and a substantial decrease in the content
of saturated esters in boron-deficient pollen tubes compared with normal pollen tubes. The FTIR spectra confirmed that boron
deficiency enhanced acidic pectin accumulation in pollen tubes, which may be associated with the increased content of carboxylic
acid. We conclude that boron has a regulatory role in pollen germination and pollen tube growth.
Keywords:
callose, cell wall, confocal microscope, FTIR, immunolabeling, pectin.
