Cell morphology and water
Corn cell structures and functions are affected by environment. Water supply to the cells influences plant function throughout its life. Imbibition of the seed initiating the cell elongation of cells and their functions occurs only when water concentration surrounding the seed is sufficient. Cell elongation driven by turgor pressure pushes the roots down and shoot up through the soil.
At about the V5 (5 visible leaf collars) the growing point differentiates into a tassel. It is all cell growth now. Cell elongation in the stem cells as well as in the leaf cells is greatly affected by water pressure within the cells. Warm wet conditions consequently result in taller plants and larger leaves. Kernel row number is set by V6 but the number of kernel ovules per ear is affected by the water pressure. Dry conditions resulting in few kernels and smaller tassels. Drought also can reduce the opening of the stomata and consequently less CO2 intake and reduced photosynthesis. Energy for the cell growth is provided by photosynthesis, the sugars guided to the various sinks in roots, leaf tips, shoots and tassel. The uppermost leaves get the direct sunlight allowing the highest photosynthetic rate. As the canopy closes in, the lowest leaves receive only a fraction of the light, sometimes not producing enough carbohydrate to meet respiratory needs for normal metabolism. These lowest leaves often become susceptible to relatively weak pathogens, develop yellow spots and drop off. By V6 stage the corn plant growing point is not putting out new cells, differentiation is over and now it is up to the dynamics of cell elongation to determine final plant development.
Genetics influence the root growth direction. Hybrids with a tendency to be highly branched near the soil surface are adapted to absorb and transport more water from organic material near the soil surface but may have trouble reaching deep into soil during drought conditions. Hybrids that tend to have fewer branches near the surface, but extremely deep roots may excel in drier conditions but can be more vulnerable to lodging in strong wind conditions.
Larger leaves, expanding due to leaf cell water supply, may have potential for more photosynthesis per plant. Larger leaves also have potential for more stomata increasing the supply of CO2 but also the loss of water via transpiration.
The corn plant’s interaction with water occurs at the cellular level. The cell’s response is affected by genetics and other environmental influences such as minerals, light intensity and pathogens. It is complicated!
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.