1   Uptake Rate

Zucchini plants have been shown to have the most successful uptake mechanisms for PCDD/PCDF's of all plants tested. This includes mechanisms that can translocate dioxins from their roots to their shoot system (including flowers and fruits), as opposed to many other plants that can only absorb dioxins into their roots.

Fig. 1: "Mean decreases in total and TEQ PCDD/PCDF concentrations in soil amended with different doses of sewage sludge (A1, A2) and urban sediments (B1–B2) before and after Cucurbita pepo L. cv ‘Atena Polka’ cultivation"³

2   Growth Conditions

Zucchini and pumpkin are very sensitive to cold weather, requires warm temperatures of above 16 degrees Celsius to grow, but to warm of a climate (above 38 degrees) will harm the plant. Zucchini takes about 60 days to mature. By then it produces fruit as long as someone picks them before they rot. Pumpkin requires between 90 to 160 days to mature. They both grow relatively quickly and, as such, have high root-uptake of nutrition from the ground. Both require moderate quantities of water to grow, which may make it more difficult to grow in drier climates; however, pumpkins have been successfully grown in Iraq, for example. Zucchini roots generally extend deeply downward in a taproot formation, while pumpkin roots tend to spread horizontally as well as vertically - most of its nutrients are absorbed from the upper 1/2 meter of the soil.

3   Plant Transformation:

Two-week-old in vitro grown Cucurbita pepo L. intact plants and cotyledons (detached and undetached from the mother-plant) were transformed by Agrobacterium rhizogenes strain NCPPB 1855, grown for 48 h at 25 °C on YMB medium. All infected material formed vigorous hairy roots in about seven days. The transformed roots were successfully grown in liquid MS medium without plant growth regulators for an indefinite number of transfers. 

4   Plant Sterility

Triploid plants have larger organs, greater biomass, and strong stress resistance by preserving relatively larger amounts of photosynthetic energy. The undesirable spread of non-native invasive crop and horticultural plants into natural areas can also be reduced or eliminated by the use of triploids, because they tend to be sterile and seedless.

There are few different ways to create triploid plants:

• - Natural selection - triploid plants occur in nature, meaning it is possible to look for the desired plant in nature.
• - Artificial hybridization - by sexual hybridization of different ploidy, one can create a triploid offspring.
• - Endosperm culture in vitro - endosperm is a triploid tissue. Successful regeneration of a plant from an endosperm tissue would result in triploid plant.

References:

1. "Cucurbita pepo L. can be transformed by Agrobacterium rhizogenes" Luigi Sanità di Toppi et al. (1997).
2. "Breeding Triploid Plants: A Review" Xiling Wang et al. (2016).
3. "Potential for Phytoremediation of PCDD/PCDF-Contaminated Sludge and Sediments Using Cucurbitaceae Plants: A Pilot Study" Magdalena Urbaniak et al. (2016).
4. "A simple method for transient transformation of pumpkin (Cucurbita maxima) seedlings" Francisco Arturo Ramírez-Ortega et al. (2015).
5. "Uptake by roots and translocation to shoots of polychlorinated dibenzo-p-dioxins and dibenzofurans in typical crop plants" Haijun Zhang et al. (2009).
6. "Planting, growing, and harvesting pumpking" The Old Farmer'S Almanac website (2010).
7. "How to Grow Zucchini: A Squash Vocabulary Lesson" Charity Shumway (2012).
8. "What Is the Life Expectancy of Zucchini Plants?" Karen Carter.