The Ultrastructure of Chloroplasts in Mineral-deficient Maize Leaves

Abstract

The ultrastructure of mesophyll chloroplasts in full-nutrient and mineral-deficient maize (Zea mays) leaves was examined by electron microscopy after glutaraldehyde-osmium tetroxide fixation. Nitrogen, calcium, magnesium, phosphorus, potassium, and sulfur deficiencies were induced by growing the plants in nutrient culture. Distinctive chloroplast types were observed with each deficiency. Chloroplasts from nitrogendeficient plants were reduced in size and had prominent osmiophilic globules and large grana stacks. Magnesium deficiency was characterized by the accumulation of osmiophilic globules and the progressive disruption of the chloroplast membranes. In calcium deficiency, the chloroplast envelope was often ruptured. Chloroplasts from potassium-or phosphorus-deficient plants possessed an extensive system of stroma lamellae. Sulfur deficiency resulted in a pronounced decrease of stroma lamellae, an increase in grana stacking, and the frequent occurrence of long projections extending from the body of the chloroplast. These morphological changes were correlated with functional alterations in the chloroplasts as measured by photosystem I and II activities. In chloroplasts of the nitrogen-and sulfur-deficient plants an increase in grana stacking was associated with an increase in photosystem II activity.Only a limited number of studies on deficiencies of the major mineral nutrients in higher plants have been concerned with the effects of the deficiency at the ultrastructural level and in particular on the fine structure of the chloroplast (8-10, 14-17). These studies have utilized a variety of plant species, a mixture of macro-and micronutrient deficiencies, and primarily potassium permanganate fixation.The present study is a report of the ultrastructural changes observed in chloroplasts in glutaraldehyde-osmium tetroxide-

Some Biochemical Characteristics of Chloroplasts from Mineral-deficient Maize

“…The significance of increased grana stacking in N-and S-deficient plants which is also associated with increased photosystem II activity is further discussed by Hall et al (7). From a functional point of view the data presented here show a correlation of high photosystem II activity with the increase in grana stack membranes seen by Hall et al (7).…”

“…From a functional point of view the data presented here show a correlation of high photosystem II activity with the increase in grana stack membranes seen by Hall et al (7).…”

“…The work of Hall et al (7) shows that some mineral deficiencies cause a distortion in chloroplast morphology. The work described below is an attempt to relate changes induced in chloroplast structure by mineral deficiencies with alterations of the composition and function of the photosynthetic apparatus.…”

“…The growth conditions have been described by Hall et al (7). The pigment composition and gross morphological symptoms of these deficient plants have been described earlier by Barr et taining the chloroplasts was suspended in a standard volume of the sucrose-Tricine homogenization medium and assayed immediately for photosynthetic activities.…”

DIEL AND SEASONAL CHANGES IN THE CHLOROPLAST ULTRASTRUCTURE OF DESCHAMPSIA FLEXUOSA (L.) TRIN.

“…Great differences in chloroplast ultrastructure have been found between plants from different biotopes and also between the sun and shade leaves of the same plant. The structure of chloroplasts is also influenced by the age of the leaves (Dodge, 1970;Hudak, 1981) and mineral nutrition (Hall et al, 1972;Platt-Aloia, Thomson & Terry, 1983). Differences in thylakoid organization are usually reflected in the chl a/b ratios of the leaves, the latter indicating differences in the distribution of chlorophyll between the chlorophyll-protein complexes (Anderson, 1980;Mel is & Harvey, 1981;Leong & Anderson, 1983).…”