Photosynthesis and starch metabolism of chloroplasts during prolonged illumination

Abstract

The starch metabolism of the chloroplasts in the leaves of Stellaria media was studied by means of electron microscopy. During the night the starch grains diminished in size but did not disappear entirely. In the light they grew due to photosynthesis. After prolonged illumination of the plant the grains almost filled up the chloroplasts. However, after an illumination of 26-27 hr a sudded disintegration took place. This was apparently caused by the increased activity of β-amylase observed in an earlier investigation to occur at this time in the chloroplasts. After the disintegration the starch grains of the chloroplasts showed irregular changes.The rate of photosynthesis and respiration was measured by an infra-red gas analyser. During prolonged illumination Stellaria media showed a rather intensive and constant rate of assimilation. The role of starch disintegration and β-amylase synthesis in making possible this constant assimilation has been discussed.

Light‐Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii

“…The photosynthetic importance of the dorsi-ventral chloroplast distribution observed in low-light control and moderate-light fronds is unknown. It can be questioned as to what extent starch-filled ehloroplasts are photosynthetically inactive (Bourdu et al 1965) or active (Haapala 1969). If starch-gorged chloroplasts are inoperative, then the extreme shade fronds would contain many more active chloroplasts per unit area than the control or moderate-light leaves.…”

Apple Fruit Removal and Limb Girdling Affect Fruit and Leaf Characteristics

“…Source-sink modification in plants leads to a better understanding of the mechanisms controlling photosynthesis and dry-matter accumulation and allocation. Starch accumulation in source leaves was reported after sink removal (Herold, 1980;Schaffer et al, 1986aSchaffer et al, , 1986b, girdling (Avery et al, 1979;Heinicke, 1932;Priestley, 1976), and continuous illumination (Haapala, 1969). The results of accumulation of starch in the chloroplasts led, in some cases, to a sharp decrease in C exchange rate (CER) due to disruption of the thylakoid membranes (Schaffer et al, 1986a).…”

Physiological observations of maize (Zea mays L.) genotypes differing in source-sink ratios

“…RuBP and PEP carboxylase activities and synthesis (Wareing et al, 1968), phosphorylase activity (Thorne, 1979), leaf chlorophyll (Kriedemann et al, 1976), inorganic phosphate (Thorne and Koller, 1974), leaf sugars (Christy and Swanson, 1976), assimilate export (Hartt et al, 1963;Swanson et al, 1976;Troughton, 1976;Chatterton and Silvius, 1979), and amylolytic activity (Haapala, 1969) have all been observed to increase following the reduction of the source. Mesophyll resistance (Thorne and Koller, 1974;Nafziger and Koller, 1976) and leaf starch (Moorby and Milthorpe, 1975) have been shown to decrease.…”