Plant cells lack chloroplasts in certain specialized cells, primarily in non-photosynthetic tissues such as roots. Here are the reasons inferred from the options you provided:
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Roots require fewer nutrients: While roots do require nutrients, this is not the primary reason for the absence of chloroplasts since chloroplasts are specifically involved in photosynthesis.
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Roots are underground: This is a significant reason. Since roots are located underground, they do not receive sunlight, which is essential for photosynthesis. Therefore, they do not need chloroplasts for the process of converting light energy into chemical energy.
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Root cells have two central vacuoles: This statement is inaccurate, as root cells typically contain one large central vacuole, which is used for storage and maintaining turgor pressure. The presence of vacuoles does not relate to the presence or absence of chloroplasts.
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Root cells have many mitochondria: While it’s true that root cells have many mitochondria (which are involved in cellular respiration to generate energy), this is also not a direct reason for the absence of chloroplasts. Mitochondria are present in almost all eukaryotic cells for energy production.
In summary, the primary reason plant root cells lack chloroplasts is that they are underground and do not receive sunlight, making photosynthesis unnecessary. Thus, their cellular functions and structures have evolved to meet their specific environmental conditions.