(BIOL 230, Lab Experiment 2)
This page is designed to help you interpret spore germination and differentiate between 1-dimensional and 2-dimensional growth in your experiment.
One Good Fern Deserves Another From Biograffitti by John M. Burns. (Quadrangle, 1975)
Prothallia of ferns are always haploid Producing sperms and eggs that seize the procreative role When, of a dampness, they unite to form a diploid.
Up springs the frondly sporophyte, with rhizome, root, and rachis And a meristem that's apical and tight. It uncoils; but on a leaf that is preparing for meiosis Sporangia in clusters make a very sori sight.
When a fern spore settles into a moist, well-protected surface, the nucleus migrates to one edge of the cell and divides to produce two cells. One is a narrow, colorless anchor called the rhizoid (see Figure 2-1). Then the large cell divides again, perpendicular to the first division to produce a protonema, the forerunner of the gametophyte. As the protonema divides, all the cell divisions are in one plane to form a 1-dimensional structure. When the cell di-visions begin to occur in two planes, the protonema is described as 2-dimen-sional. Ultimately, the protonema develops into a delicate, heart-shaped gametophyte called the prothallium. This photosynthetic, haploid plant produces rhizoids on its lower surface, and for a time, it lives as a completely independent plant. Eventually, the prothallium produces antheridia (sperm-producing plants) and archegonia (egg-producing plants).
Development of fern spores is controlled by light and water. In this exercise, we will look at photomorphogenesis, that is, the effects of wavelength (photo) on fern spore germination and protonema development (morphogenesis). Note, this is not the same as (1) photosynthesis, the production of energy using light, or phototropism, the directional growth in response to directional light. Shoots are positively phototropic (grow toward light) while roots often show negative phototropism (grow away from light).
Germination. One brown spore has produced a protonema. (Note the brown spore coat, colorless rhizoids, chloroplasts, and cross wall.). Click for a labeled photo.
1-dimensional growth. Note that the cross walls are parallel to each other making a protoneme that is only one cell wide. Click here to see a diagram or a labeled photo.
2-dimensional growth. Look at the last cell in the protoneme shown above. The cross wall is perpendicular to the other.
In the picture shown below, the protoneme produced 6 cells in one dimension before making cross walls in the second dimension. Labeled photo.
Photo: V. Moala Spring 2013
Photos on ../fern ©CLCase
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