Carl A. Huetteman

Thidiazuron: a potent cytokinin for woody plant tissue culture

Thidizuron (TDZ) is among the most active cytokinin-like substances for woody plant tissue culture. It facilitates efficient micropropagation of many recalcitrant woody species. Low concentrations (<1 µM) can induce greater axillary proliferation than many other cytokinins; however, TDZ may inhibit shoot elongation. In some cases it is necessary to transfer shoots to an elongation medium containing a lower level of TDZ and/or a less active cytokinin. At concentrations higher than 1 µM, TDZ can stimulate the formation of callus, adventitious shoots or somatic embryos. Subsequent rooting of microshoots may be unaffected or slightly inhibited by prior exposure to TDZ. The main undesirable side effect of TDZ is that cultures of some species occasionally form fasciated shoots. The high cytokinin activity and positive response of woody species to TDZ have established it as among the most active cytokinins forin vitro manipulation of many woody species.

In vitro embryonic axis and seedling shoot tip culture of Juglans nigra L.

Embryonic axes and seedling shoot tips of Juglans nitra L., Black walnut, were cultured in vitro. Significant variation existed among progeny from individual trees for growth of radicles and epicotyls and production of callus and axillary shoots from embryonic axes. The concentration of 6-benzyladenine influenced the growth of the radicle and epicotyl and production of callus and axillary shoots of axes. Axes generally initiated growth quicker on solidified woody plant medium than on Driver and Kuniyukis walnut medium, but axillary shoot proliferation and elongation were eventually better on liquid Driver and Kuniyukis walnut medium than on woody plant medium which required an etiolation treatment for microshoot elongation. The concentration of BA also influenced both callus growth and axillary shoot proliferation from seedling shoot tips. Axillary shoots which formed in Driver and Kuniyukis walnut medium rooted best in sterile vermiculite following a 15 s dip in 10 mM indole-3-butyric acid. Micropropagated plants are growing in the greenhouse.

Nursery establishment, phenology and growth of silver maple related to provenance.

Abstract Establishment, phenology, early survival and growth are reported for 10 silver maple ( Acer saccharinum L.) provenances densely planted in a nursery near Carbondale in southern Illinois. Seed from southern parts of silver maples range planted in May established well to form dense plantings and seed from northern areas planted in June established poorly. Saplings of the northern provenances commonly had earlier terminal bud set and leaf loss. Spring bud break tended to be earliest for southern provenances. Basal caliper and mean tree weights were greater in plots of the northern plantings. Height and total plot weights were greater in plots of the southern provenances. Trees in four blocks were harvested after two years to determine tree weights and coppice potential. Height growth increment in the unharvested (control) block was greatest in the second of the four years observed.