Plant Physiology

The dark reaction, also known as the Calvin cycle, occurs in the stroma of chloroplasts and does not require light directly. It synthesizes PGAL (phosphoglyceraldehyde), a three-carbon sugar, by fixing atmospheric CO\textsubscript{2} using ATP and NADPH produced during the light reactions.
- ATP formation and oxygen evolution occur during light reactions.
- Hydrogen evolution is not part of photosynthesis.

Plants absorb minerals from the soil primarily in ionic form dissolved in water. These mineral ions, such as nitrate (NO\textsubscript{3}\textsuperscript{-}), phosphate (PO\textsubscript{4}\textsuperscript{3-}), potassium (K\textsuperscript{+}), and others, are taken up by root hairs through active and passive transport mechanisms.
- Minerals are not absorbed in solid or gaseous form.
- Liquid form is a medium but not the chemical form absorbed.

Photoperiod, the duration of light and dark periods in a day, influences flowering in many plants. It regulates the timing of flowering by triggering physiological responses.
- Soil water content and acidity affect plant growth but are not direct factors controlling flowering time.
- The amount of green pigment (chlorophyll) relates to photosynthesis, not flowering control.

Endosperm is a tissue produced inside seeds of most flowering plants following fertilization. It provides nutrition, in the form of starch, oils, and proteins, to the developing embryo (fetus) within the seed.
- The seed contains the embryo and endosperm.
- The fruit develops from the ovary and protects the seed.
- Andosperm is not a correct term here.

C4 plants have a higher rate of photosynthesis compared to C3 and CAM plants due to their specialized mechanism that efficiently fixes CO\textsubscript{2} even under high temperature and light intensity conditions. This adaptation minimizes photorespiration and increases photosynthetic efficiency.
- C3 plants have lower photosynthetic rates under such conditions.
- CAM plants fix CO\textsubscript{2} at night to reduce water loss but generally have slower photosynthesis rates.

Bulliform cells are large, bubble-shaped cells present in the mesophyll tissue of grass leaves. They help in folding and unfolding the leaf blade to reduce water loss during drought conditions.
- Bundle sheath surrounds vascular tissue.
- Vascular tissue transports water and nutrients.
- Epidermis is the outer protective layer.