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Fifty-two plant species, covering some Gymnosperms and all the key groups of Angiosperms, were chosen for surveying their intrinsic beta-glucuronidase-like activities. Histochemical (overnight incubation) and qualitative fluorometric (24 h incubation) assays indicated that, with few exceptions, such activities were detected in certain part(s) of the fruit walls, seed coats, endosperms or, especially, the embryos of the tested plants. Most of such activities in the excised immature embryos of soybean and string bean disappeared after one to a few days' in vitro culturing. Such activities in the intact mature seeds of these two species diminished also during germination process. The vegetative organs of seedlings/mature plants usually lack such activities. The enzyme(s) responsible for such activities was antigenically dissimilar to E. coli beta-glucuronidase.

Soybean is a recalcitrant species for in vitro manipulation. Chinese scientists developed two in planta non-tissue culture soybean transformation procedures: (1) via the "pollen-tube-pathway" to introduce exogenous genomic total DNA of Glycine gracilis, the seed of which consisted of 50% protein, and (2) "ovarian injection" with exogenous plasmid DNA containing atrazine-resistant gene. A high yield and high seed protein (45.44%) cuhivar, 'Heisheng 101', resulted from the first method, and atrazine-resistant F~, F2, and F 3 plants were obtained from the second method. Both exogenous single-genic Mendelian traits and multi-genic quantitative traits were transferrable with these simple and inexpensive procedures. However, some controversy exists with the acceptance of these novo procedures; mainly because instead of the standard Southern blotting, the RAPD and dot blotting techniques were used in the molecular confirmation of the transgenic status in the reported studies.