308 



BIOCHEMICAL SYSTEMATICS 



In addition to valuable new agronomic characters, some plants of these 

 hybrids exhibit new morphological characters not found in either of 

 the parents. These arise as mutations and come to be inherited later. 

 Remote hybridization acts as a kind of stimulus for the mutation 

 process. 



In some ways the results are suggestive of the classical example 

 of cytoplasmic inheritance in Streptocarpus (Oehlkers, 1938). In this 

 genus certain inter-specific hybrids have staminodia transformed into 

 fertile carpels. While increased mutation rate represents one possible 

 explanation of the results, it is probable that some other form of 

 genome interaction, not necessarily involving mutation, is responsible. 



Some interesting results have been reported from different 

 sources indicating the dominance of more complex compounds over 

 simpler ones within a general class. Related to this situation is 

 the observation, also from several investigators working with different 

 materials, that when two species differ in the specific representative 

 of a biochemical class present, their hybrid contains both substances. 

 Neither result is incompatible with generally accepted principles of 

 biochemical genetics, nor are they mutually exclusive. At the generic 

 level Delaveau (1961) reported that in a hybrid between Raphanus and 

 Brassica species-specific mustard oils occurred together. 



One of the most important studies of biochemical components 

 of natural hybrids is that of Mirov (1956) who studied natural hybrids 

 of Pinus contorta (lodgepole pine) and Pinus banksiana (jack pine). 

 Trees intermediate between lodgepole and jack pine were discovered 

 over part of central Alberta, representing an area roughly 150 by 200 

 miles. The ranges of the two species overlap in this region. Artificial 

 hybrids have been produced (Righter and Stockwell, 1949), and these 

 are said to be morphologically intermediate. 



The significant biochemical comparisons involved the terpen- 

 oid contents of the two species and their hybrids. Lodgepole pine 

 turpentine consists almost entirely of /8-phellandrene and is 

 levorotatory. 



CH2 



II 



/^\ 

 H2C CH 



I II 



H2C CH 



CH 



A 



H3C CH3 



yS-phellandrene 



