7 – Biology HL Internal Assessment (IA) – May 2022

How does an increase in concentration of zinc sulfate (0, 0.01, 0.02, 0.03, 0.04mol/dm3) affect the rate of Glycine max L. seed germination, as quantified by the number of seeds germinated over 5 days?

Introduction

Growing up as a Korean, soybean sprouts were common banchan for our family. This was applicable even in ______________________, thanks to its “small but increasing production of soybeans” and its soybean grain exports that doubled in 2012 with “farmers producing significant quantities to satisfy the demand of large ships to export markets in Europe, Africa, and Asia” (_________________________ ). Incidentally, ___’s mineral production in 2018 was valued at $327 million, which “increased from $125.8 million in 2017, and also set a new record for the province” (“Mineral Production”). However, it was reported in 2019 that “The Department of Lands and Forestry has not completed sufficient site investigations on all abandoned mine sites identified with potential areas of contamination […] resulting in unaddressed human health or ecological concerns” (Pickup). With the ongoing industrialization and mining activities of zinc, gold, coal, and gypsum in our province, I was concerned about the resulting environmental consequences that would impact not only the ecosystem but also the life of various local communities. Therefore, knowing that “most environmental contamination and human exposure result from anthropogenic activities such as mining […] and domestic and agricultural use of metals and metal-containing compounds,” I wanted to investigate the effect of heavy metals, especially zinc in form of zinc sulfate (ZnSO4), on growth and nutrient quality of soybeans, a type of plant typically found in my surroundings (Tchounwou et al.).

Background Information

Glycine max L., commonly known as soybean, was investigated in this experiment. These dicotyledonous seeds emerge two cotyledons once germinated and comprise the following structure (Naeve):

During germination, soybeans absorb nutrients for about 50% of their weight, and a seed coat called testa begins the process with water uptake (“Soybean Production Handbook”). Before releasing the developing embryo, testa supports the zygote with water, oxygen, minerals, and phytohormones such as abscisic acid (ABA), auxin (IAA), and gibberellins (GAs) necessary for growth (Smýkal et al.). Phytohormones then synthesize hydrolytic enzymes that result in “hydrolysis of stored starch, lipid, protein hemicellulose, polyphosphates, and other storage materials” (Ali and Elozeiri). Further, those seed reserves are mobilized and catalyzed to provide the radicle with “energy and biochemical precursors needed for growth,” eventually succeeding germination with radicles (Li et al.)…