The Effect of Auxins on Pinus contorta Seedling Root Development

Primary lateral root production on Pinus contorta seedlings was increased 5–10 fold by immersion in auxin solutions. Watering auxin solutions onto P. contorta seedlings growing in soil or compost induced the development of large numbers of primary lateral roots in the root collar region. The number of primary lateral roots which developed depended mainly upon the auxin used and its application rate, seedling age and to a lesser extent on the soil characteristics. Instability of transplanted pines is partly due to their lack of primary lateral roots and their inability to regenerate new ones after planting out; this instability may be overcome by using auxin treated seedlings. Potential practical applications of this technique are discussed.