gene vectors for higher plants has been the difficulty of 
regeneration of whole plants from transformed plant cell lines. 
Cloned gall-forming lines of tobacco cells containing wild type 
nopaline plasmid pTiT37 T-DNA spontaneously, or upon cytokinin 
induction, regenerated shoots that displayed varying degrees of 
normalcy upon grafting onto healthy host plants. Such shoots 
synthesized nopaline, failed to form roots, and were resistant to 
superinfection by A. tumefaciens . When fertile, these grafted 
shoots produced seed that gave rise to normal plants that lacked 
nopaline, produced roots and were sensitive to A. tumefaciens, as 
well as seeds that would not produce intact plants. The normal 
plants did not contain T-DNA due to Mendelian segregation of the 
T-DNA. Similar results have been obtained in studies of- tobacco 
cells transformed in vitro by either octopine or nopaline type T- 
DNA. In such experiments, opine-positive plant cells with roots 
were not obtained, and shoots obtained by grafting were usually 
both opine-positive and resistant to superinfection by 
A. tumefaciens . One example has been reported of opine-positive 
complete plants regenerated from a crown gall tumor initially 
incited by a shooty mutant of octopine T-DNA. These plants 
segregated the octopine trait in Mendelian fashion to healthy 
progeny, evidence that T-DNA was situated in chromosomes of 
the parental tissue. However, the T-DNA in these plants was 
found not to be full length. A large deletion of the central part of 
T-DNA apparently gave rise to plant cells with little T-DNA 
except for the octopine synthase gene. In experiments conducted 
by Agracetus it has been shown that it is possible to remove 
Environmental Assessment 
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