Root Development in Aluminous Hawaiian Soils 1 
D. L. Plucknett , 2 J. C Moomaw , 3 and C. H. Lamoureux 4 
ABSTRACT: Roots of Rhodomyrtus tomentosa and Melastoma malabathricum 
were excavated in three soil series from the bauxitic area of Kauai. Root systems 
of R. tomentosa and M. malabathricum in Kapaa and Halii soils were very shal- 
low, with tap roots turning laterally at shallow depth and with long lateral roots 
very close to the soil surface. Deeper tap-root penetration of R. tomentosa and 
M. malabathricum was observed in the Koolau soil. 
Lime and phosphorus treatments were added to bauxitic subsoils of the Kapaa 
and Halii series in pots and Leucaena glauca ( L. ) was planted in the pots. Tap roots 
of L. glauca were stimulated by phosphorus treatment, but were restricted in 
untreated subsoils. Increased root development with phosphorus treatment seemed 
to be more related to phosphorus supply than to decreased aluminum effects. No 
evidence of root damage due to aluminum was found. 
L. glauca roots were sectioned with a freezing microtome and stained, using 
hematoxylin without a mordant. Although all staining obtained could not be at- 
tributed to aluminum, since other metals can act as mordants for hematoxylin, 
intensity of staining was assumed to be related to aluminum concentration in the 
tissues. Cell walls, nuclei, and cytoplasm stained in all tissues, and outer walls of 
epidermal cells stained very heavily. Staining was more intense in roots from check 
and P-treated plants than in roots from lime-treated plants. 
Studies of the root development of natural 
plant communities (Weaver 1920, Weaver 
and Albertson 1943, Weaver and Darland, 
1949) and of cultivated plants (Weaver, 1926; 
Troughton, 1957; Crider, 1955) under a vari- 
ety of conditions and treatments, are well 
known to ecologists. Normally, a well-devel- 
oped root system is essential to the vigor- 
1 Published with the approval of the Director of 
the Hawaii Agricultural Experiment Station, Univer- 
sity of Hawaii, as Technical Paper 583. Manuscript 
received June 8, 1962. 
3 Department of Agronomy and Soil Science, Uni- 
versity of Hawaii. 
3 Department of Agronomy and Soil Science, Uni- 
versity of Hawaii. Present address: The Interna- 
tional Rice Research Institute, Manila Hotel, Manila, 
Philippines. 
4 Department of Botany, University of Hawaii. 
ous growth and successful competition of the 
dominants in most plant associations. Shallow- 
rooted plants, however, are known from many 
different habitats, especially those with poor 
physical properties but also from those with a 
low nutritional status with respect to nitrogen, 
phosphorus, calcium (Fox, Weaver, and Lipps, 
1953) and potassium (Haynes, 1943). Root 
damage and restricted root development in such 
crop plants as barley and tobacco have been 
associated with high levels of soil aluminum, 
but little is known of root development in un- 
cultivated plants growing in soils with high 
concentrations of active aluminum. 
In a study of vegetation on gibbsitic Ha- 
waiian soils Moomaw and Takahashi (I960) re- 
ported shallow root systems, but detailed studies 
of root development and distribution in these 
398 
