The deficiencies of micronutrients, not only affects the growth of plant but also vital functions such as photosynthetic and mitochondrial electron flow. Among the list given below, which group of three elements shall affect most, both photosynthetic and mitochondrial electron transport.

As a plant nutrient, copper seems to function primarily as a cofactor for a variety of oxidative enzymes. These include the photosynthetic electron carrier plastocyanin; cytochrome oxidase, which is the final oxidase enzyme in mitochondrial respiration. 
Iron is part of the catalytic group for many redox enzymes and it is required for the synthesis of chlorophyll. Important redox enzymes include the heme-containing cytochromes and non-heme iron-sulfur proteins (e.g., Rieske proteins, ferredoxin, and photosystem I) involved in photosynthesis, respiration and nitrogen fixation.
Manganese is required as a cofactor for a number of enzymes, particularly decarboxylase and dehydrogenase enzymes, which play a critical role in the respiratory carbon cycle. The best known and most studied function of manganese is in photosynthetic oxygen evolution. In the form of a manganoprotein, manganese is part of the oxygen-evolving complex associated with photosystem II, where it accumulates charges during the oxidation of water.