EFFECTS OF COPPER TOXICITY ON DIFFERENT GROWTH ATTRIBUTES OF PHLOX DRUMMONDII

Heavy metal contamination is one of the major problems prevailing in environment. Copper in high concentration is considered to have serious effects on plant growth parameters which results in chlorosis, disturbed mineral uptake and stunted growth. A pot experiment was conducted to evaluate the ability of Phlox drummondii to tolerate and accumulate high copper doses. Plants were exposed to copper toxicity at three different concentrations (10 ppm, 20 ppm and 30 ppm) by using copper sulfate (CuSO4.5H2O). Results showed that chlorophyll-a, chlorophyll-b, total chlorophyll and carotenoids of treated plants decreased significantly (p˂0.05) with the increase of copper concentration. Selected copper levels showed no effect on plant height, number of leaves, leaf area and ascorbic acid (p>0.05). Relative water content increased significantly (p˂0.05) as compared to control plants. Copper uptake by roots of treated plants was greater as compared to control plants indicating Phlox drummondii ability to grow well in the copper contaminated soils and could be classified as copper tolerant plant. Copper tolerance by phlox was associated with its capacity to absorb and accumulate in roots preventing translocation of metal to other photosynthetic tissues. Therefore, Phlox drummondii has the characteristic to be used as hyperaccumulator by vegetating in copper contaminated soils. Further studies at genetic level would play a key role in understanding the tolerance mechanism of Phlox drummondii towards copper contamination.

Seed Production of Annual Phlox

Phlox drummondii Hooker, commonly known as annual or Drummond phlox is one of north and central Florida's showiest and most reliable spring flowering annuals. This document is ENH 1020, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date December 23, 2005.

Correlated evolution of self and interspecific incompatibility across the range of a Texas wildflower

Plant species have repeatedly evolved recognition systems between pollen and pistils that identify and reject inappropriate matings. Two of the most important systems recognize self-pollen and interspecific pollen. Outstanding questions are whether and how these two recognition systems are linked and if this association could constrain the evolution of mate choice. Our study characterizes variation in self and interspecific incompatibility in the native range of the Texas wildflower Phlox drummondii. We found quantitative variation in self-incompatibility and demonstrate that this variation is significantly correlated with variation in incompatibility with its close congener P. cuspidata. Furthermore, we find strong evidence that self and interspecific incompatibility involve common mechanisms of pollen adhesion or early pollen-tube germination. Finally, we show that P. drummondii populations that co-occur and hybridize with P. cuspidata have significantly higher interspecific incompatibility and self-incompatibility than isolated P. drummondii populations. This geographic variation suggests that the evolution of self-compatibility is constrained by selection favoring interspecific incompatibility to reduce maladaptive hybridization. To our knowledge this is the strongest evidence that a correlation between variation in self and interspecific incompatibilities could influence the evolution of pollen recognition across the range of a species.