What part of the plant contains the desired substance?

Question

BlackTom AI · Accepted Answer

Bark contains many of a plant’s stored secondary compounds (tannins, resins, alkaloids) and protective tissues, so it is the correct source of the desired substance.

1. Relevant knowledge points and concepts
- Plant organs and primary functions: roots (absorption and storage of water/nutrients and some storage compounds), leaves (photosynthesis, gas exchange), flowers (reproduction, attractants like nectar and volatile compounds), bark (outer stem layer composed of phloem, cambium, and protective tissues; site of transport and many secondary metabolites).
- Secondary metabolites (e.g., tannins, quinine, salicin, resins) are often concentrated in bark because bark protects the vascular system and deters herbivores/pathogens.

2. Step-by-step reasoning
Step 1: Identify what kinds of plant parts typically contain extractable medicinal or protective substances. Step 2: Compare functions: leaves make sugars, roots store carbohydrates and absorb, flowers produce reproductive tissues and attractants, bark synthesizes/stores defense compounds. Step 3: Match “desired substance” (commonly a protective or medicinal compound) to the organ most likely to contain it: bark.

3. Intermediate steps / no numerical calculations
- No numerical computation is required. The logical intermediate steps are: classify organ functions → determine where target compounds accumulate → select bark as the organ matching accumulation of secondary protective compounds.

4. Why the correct answer is correct
Bark houses phloem and storage tissues and accumulates defensive and medicinal compounds; historically many important extracts (e.g., quinine from Cinchona bark, salicin from willow bark) come from bark. Because the desired substance fits the profile of a bark-localized compound, bark is the correct choice.

5. Why the other options are incorrect
- Root: mainly for uptake and storage of primary metabolites; less commonly the source of certain targeted protective compounds in this context.  
- Leaves: mainly photosynthesis and transient metabolites; not the typical long-term storage site for many medicinal secondary metabolites.  
- Flowers: specialized for reproduction and attractants; they produce volatile compounds and nectar, but are not the usual source of the described “desired substance.”

6. Conclusion
The evidence and organ functions confirm that Bark is the correct answer. This matches the provided answer: Bark.

What part of the plant contains the desired substance?单项选择题

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