Question

The symptoms of magnesium deficiency appear first in the mature leaves
A. True
B. False

Answer 1

Magnesium deficiency is a damaging plant disease that most typically happens in highly acidic, light, sandy soils where it would be quick to leach away magnesium. Magnesium can be precipitated by excessive luminal phosphate or fat and reduced absorption.

Complete answer:
The first indication of magnesium deficiency is the aged leaves called chlorosis (yellowing of leaf tissue due to a lack of chlorophyll) that progress to the young leaves as the deficiency extends as it forms the chlorophyll's central atom. Thus, it is a valid statement that the signs of magnesium deficiency occur first in the mature leaves. The plant first must break down chlorophyll in older leaves due to the extreme mobile nature of magnesium and move the Mg to younger leaves that have greater photosynthesizing needs. The chlorosis of old leaves, which extends to the young leaves as the deficiency progresses, is also the first symptom of magnesium deficiency. For several key enzymes, including ribulose bisphosphate carboxylase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC), both essential enzymes in carbon fixation, magnesium often acts as an activator.

So, the correct answer is option (A)

Additional Information:
The amount of magnesium that can be consumed by the plant depends on its concentration in the soil solution and the soil's capacity to replenish the soil solution with magnesium. The abundance of magnesium is restricted by issues such as low soil pH, low temperatures, dry soil conditions, and elevated levels of competing elements, such as potassium and calcium. Magnesium deficiency seems to be more prone to such conditions. Symptom interpretation depends to a great extent on the intensity at which the leaves are exposed to light. More signs can be exhibited by defective plants that are exposed to a high intensity of light.

Note: Low levels of Mg result in a decrease in plant photosynthetic and enzymatic activity. In maintaining ribosome structures, magnesium is also critical, so a lack of magnesium triggers ribosome depolymerization that contributes to premature plant aging. Necrosis and falling of older leaves occur upon persistent magnesium deficiency. Magnesium deficient plants produce smaller, woodier fruits.