The amino acids pool in the style of self-incompatible strains ofPetunia after self- and cross-pollination

Abstract

Shifts in the composition of amino acid patterns in the styles ofPetunia hybrida were investigated during incompatibility reactions after self pollination. High organ specificity (leaves, unpollinated styles, pollen) was observed, along with a high content of free tryptophane and proline in the pollen. In unpollinated styles slow protein synthesis takes place during the first 24 hour period after their removal from the plant. After cross pollination a slight decrease in net protein content is seen which is due to the presence of penetrating pollen tubes. An increase noted in the concentration of amide containing groups can be linked to protein and amino acid degradation. In the first 12 – 18 hrs. after self pollination protein synthesis stops abruptly, to be resumed again slowly after 20 hrs. This change does not correspond to an alteration in free amino acid concentration. In pollinated styles the amount of free amino acids from protein degradation is much higher than the actual increase of amino acid concentration, especially after selfing. This must mean that the amino acids resulting from protein hydrolysis are used up as an energy supplying substrate. There is evidence for the existence of two different amino acid pools in the style: a storage pool to serve as source of oxygen for respiration, and another small pool which provides amino acids for protein synthesis. In a style penetrated by growing pollen tubes evidence of compartmenting and metabolic channeling has been obtained, thus variation in the free amino acid pool is the physiological expression of pollen tube growth. The striking increase of the tryptophane concentration, especially after outbreeding, seems to be linked to the metabolism of growth hormones of the indole group. The specific influence of incompatible pollen tubes on the amino acid pools is discussed in connection with recent theories on the physiological mechanism of gametophytic incompatibility and the formation of allosteric molecules as genetic regulators of inhibitor synthesis.