Some Effects of Boron on Root Growth
Australian Journal of Biological Sciences
The absence of boron in the root environment reduced the total linear growth of the radicles of the four dicotyledon and one monocotyledon species studied. After growth for 4 days in a boron-free medium, the growth rate of the maize radicle was comparable to that in a plus-boron medium, whilst the growth of the field bean radicle ceased. The minimum boron requirement for the unrestricted growth of the field bean (Vicia faba val'. minor) radicle over 120 hI' was 0·005 p.p.m. B. Each microgram of
... . Each microgram of boron in this medium evoked a mean radicle elongation of 51 mm. Chemical analysis and the growth response of beans upon transfer from plus-boron to boron-free solutions demonstrated that, despite a higher concentration of boron in the radicle tip (as in other young tissues), the reserves of boron in the radicle tip were sufficient to support only about 5 hI' of growth at the plusboron growth rate. Feeding experiments and seed analysis, coupled with growth studies, showed that there was little movement of boron from either the seed to the radicle or from the epicotyl to the radicle tip. No regrowth occurs from the tips of radicles immersed for 72 hI' or more in solutions lacking boron. An analogy is suggested between the effects of boron deficiency and X-irradiation on the bean root tip. The influence of boron deficiency on lignification and differentiation in the bean radicle is discussed.