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Relationship between nuclear DNA content cell volume and cell water relations in Microseridinae (Asteraceae: Lactuceae)
Physiological and anatomical mechanisms to water stress were determined in leaves of four diploid Microseridinae species differing in nuclear DNA content. In diploid species of Microseridinae, there is a direct correlation between DNA content and environmental water availability, i.e., low DNA content species are associated with more drier habitats and high DNA content species are found on mesic environments (51). An objective in this research was to determine if a correlation between genome size and cell volume is present in differentiated tissues of leaf parenchyma cells. The research was done on water-stressed (S) and non-stressed (NS) plants to assess the effect of water stress on cell anatomy and leaf area in Microseris and P. multicaulis plants. A cyclic water stress of six-day long over a twenty four day period induced turgor maintenance and accumulation of solutes, particularly amino acids and glucose in S leaves of low DNA content M. bigelovii plants. The solute accumulation induced osmotic adjustment in the S plants accompanied with some tissue dehydration. Osmotic adjustment was not observed in high DNA content M. laciniata S plants. Leaf mesophyll cells of M. laciniata exhibited significant increase in tissue elasticity, significant decrease in cell volume, cell wall thickness, and lower transpiration rates when differentiated under water stress. M. bigelovii S plants, did not exhibit significant changes in leaf mesophyll cell volume, wall thickness and/or tissue elasticity. Leaf transpiration rates of S plants were significantly higher compared to those of M. laciniata S plants. The results suggest that high DNA content plants maintain turgor by reduced cell volumes and increased tissue elasticity, whereas low DNA content plants appear to accomplish turgor maintenance with osmotic adjustment.
Includes bibliographical references (leaves 110-116).