Growth (Plants)

The aim of this study was to determine the effects of nutrient supply and artificial
defoliation on the growth rate of water hyacinth. The plants were subjected to two levels
of nutrient (high and low) and three levels (0%, 10% and 80%) of defoliation treatment.
The effect of the nutrient and repeated defoliation treatments was detem1ined after six
weeks. Ten percent defoliation did not show any significant difference from control
plants in biomass allocation or relative growth rate (RGR) in either nutrient
concentration, while 80% defoliation caused a significant decrease in the final RGR
under high and low nutrient treatments. High nutrient treatment resulted in higher RGR
and allocation to asexual reproduction, resulting in higher biomass accumulation
compared to the low nutrient treatment, which had higher root growth and allocation to
sexual reproduction. My data provide evidence that water hyacinth can fully compensate
to low levels of defoliation.

I conducted a greenhouse study in order to examine the effects of hydrology
and its interaction with gibberellic acid (GA3) on the invasive exotic Lygodium
microphyllum (Old World climbing fern) growth and physiology. Three hydrological
(flood, drought and field capacity) and three hormonal (gibberellic acid, paclobutrazol
and water) treatments were studied using a 3x3 factorial experimental design. Plants
under flooded conditions had a significantly lower relative growth rate compared to
plants under field capacity or drought. Plants under flooded conditions showed a
significantly lower specific leaf area and area-based photosynthetic rate than plants
under field capacity and drought treatments, resulting in significantly lower massbased
photosynthesis. Overall, the variation in growth response to treatments was
most explained by mass-based photosynthesis (r^2=0.66). Treatments with gibberellic
acid or paclobutrazol (GA inhibitor) resulted in no differences in growth as compared
to untreated plants.