BIOL2370 Practical 5

There was no significant difference in the mean root mass among the treatments applied to corn seeds. But, for the Root_mass variable, which treatment showed the highest numerical mean, and what can be statistically concluded about this difference relative to the Control mean?

• KNO3, it is significantly heavier than the Control.

• Control; it is the most precise measurement due to the small Std. Error.

• Hydro-priming; but the confidence intervals overlap, meaning the difference is not statistically significant.

• CaCl2; this indicates a true physiological advantage for early root development.

In the corn seeds, The mean for Cot/Seed_mass in the Control and CaCl2 groups is negative (-0.027 and -0.028). Assuming this variable represents the difference (Mass at day 7 - Mass at day 3), what does a negative mean mass most logically imply?

• The sample size was too small to measure the mass accurately.

• CaCl2 treatment caused mass to convert into kinetic energy.

• The experiment failed to run for a long enough duration.

• The seed storage tissue experienced a net consumption (catabolism) of stored material during the period.

Based on the results from corn, the Hydro-priming group showed the longest Shoot_length (23.640 mm/day) and the highest Root_mass (0.680 g/day). Given the lack of statistical significance, what is the best biological interpretation of this observation?

• Hydro-priming is the superior treatment, but the experiment was underpowered (low n).

• The plant is inherently more sensitive to water than to chemical treatment.

• Any measured physiological advantage is likely due to random sampling rather than a true effect of the priming treatment

• Corn growth is highly dependent on an external nutrient supply during early germination.

In a dicot like the bean, the cotyledons serve as the primary storage organs. A major physiological event that occurs before radicle emergence but after imbibition is the synthesis of hydrolytic enzymes. What is the main function of these enzymes?

• To create a Ca2+ gradient for cell wall synthesis in the hypocotyl.

• To promote the final stage of maturation drying by restricting water flow.

• To break down stored macromolecules (e.g., starch, protein, lipids) into usable sugars and amino acids for embryonic growth.

• To regulate the (ABA) Abscisic Acid concentration to maintain dormancy.

The Control treatment yielded significantly taller shoots (53.933 mm/day) compared to all primed groups/treatments (see Tukey post hoc table). Given that priming often improves germination, the most likely biological explanation for this result is:

• The Control group received external nutrients not available to the primed groups.

• The priming process introduced a secondary stress that retarded early cell division and elongation in the shoot of otherwise compromised seeds.

• Beans are monocots and inherently respond poorly to osmotic agents.

• The cotyledons were removed during the priming process, limiting the energy supply.

The (Cot\seed_mass) variable in the beans has the largest (Std. Error) (0.637) across all treatments. What does this high variability relative to the means suggest about the biological process being measured?

• Cot\seed_mass is strongly positively correlated with Root_mass

• The (Cot\seed_mass) variable is statistically stable and shows reliable consumption across all treatments.

• The rate or extent of seed reserve consumption varies greatly between individual bean seeds regardless of the priming treatment.

• The control group is likely an outlier and should be removed from the analysis.

Both KNO3 and CaCl2 are commonly used for osmo-priming. KNO3 primarily provides the essential nutrient Nitrate NO3- to the embryo, which is crucial for the early synthesis of:

• Cell wall cellulose and hemicellulose for structural integrity.

• Proteins, nucleic acids, and amino acids to support rapid metabolic growth.

• Primary carbohydrates (sucrose and glucose) for energy transport.

• Fatty acids and lipids for membrane formation.

From the results in the tetrazolium tests (see photo), which option correctly identifies the primary area of viable, pink-to-red staining in each seed?

• Corn: Entire endosperm; Bean: Seed coat (testa).

• Corn: Embryo; Bean: Embryo and cotyledons.

• Corn: Aleurone layer; Bean: Vascular tissue within the cotyledons.

• Corn: Seed coat and pericarp; Bean: Only the hypocotyl.

Both corn and bean seeds were boiled before being subjected to the TTC test and showed no staining. This result functions as a crucial negative control, confirming which of the following about the viability test itself?

• TTC cannot penetrate the cell walls of non-viable seeds.

• The pink staining is specifically due to a biological, enzyme-driven process and not a general chemical reaction with dead, passive tissue.

• Boiling promotes the conversion of starch to sugar, interfering with the TTC reaction.

• The heat from boiling denatured the TTC solution, rendering it ineffective.

Why does boiling the corn and bean seeds prevent any TTC staining, even if the seeds were perfectly viable before heating?

• Boiling hydrolyzes the insoluble TTC (Triphenyl Tetrazolium Chloride) into its constituent chemicals.

• Boiling removes the necessary water molecules required for the final TTC reduction reaction.

• The high heat denatures the active dehydrogenase enzyme proteins.

• Boiling promotes the synthesis of Abscisic Acid (ABA), which inhibits respiration.