PHOTO- AND THERMO-SUSCEPTIBLE CHLOROPHYLL MUTANTS OF PISUM SATIVUM

PNL Volume 18 1986 RESEARCH REPORTS

Gottschalk, W.

Institute of Genetics, University of Bonn

Federal Republic of Germany

The penetrance and expressivity of many mutant genes controlling

chlorophyll content of plants depends on temperature. Examples are known

in Avena, Hordeum, Tagetes, and Arabidopsis, among others. In other cases,

light intensity influences the action of chlorophyll genes. Examples of

this may be found in mutants of Lupinus, Lycopersicon, Antirrhinum, and

Arabidopsis.

The X-ray induced mutant 159 of our collection belongs to the first

group. The plants are almost free of chlorophyll when grown under normal

field conditions. They die after having formed four small leaves, behaving

like typical lethal mutants. The lethal effect of the recessive gene,

however, can be overcome by growing the mutant under higher temperatures.

In phytotron trials, mutant plants were chlorotic at temperatures below 17C

whereas normal chlorophyll synthesis occurred at 19C and higher.

A representative of the second group is mutant 11A of our collection

which appears identical with Lamprecht's albina terminalis (alt) mutant

(1). When grown in the field, the lowest three or four foliage leaves have

normal dark green chlorophyll content. The fourth leaf is light olive

green and the leaves above are almost free of chlorophyll. The plants form

9-10 leaves but die before flower buds are formed. Degeneration of

chlorophyll typically occurs above the fifth foliage leaf.

However, the pattern of chlorosis just described appears only under

normal insolation. When the plants are grown in pots in dim light, they

also produce normal leaves in the upper region of the shoot. If these

plants are returned to normal light, the newly formed leaves again show

chlorosis. Thus, light conditions strongly influence the expression of

mutant 11A.

Lamprecht, H. 1955. Agri Hort. Genet. 13:103-114.

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