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26 Other Investigations Several investigations other than those needed to solve specific problems are desirable. A survey of diurnal gas exchange in plants would probably be beneficial. The objective would be to identify plants that have Crassulacean acid metabolism. Such plants may have agricultural im- portance. Other subjects worthy of study: ⢠Water relations and protoplasmic drought resistance in tropical forests ⢠Germination of natural vegetation in arid climates ⢠Physiological and biochemical effects of drought on plant me- tabolism ⢠Re-establishment of plants in areas that have only fog pre- cipitation
27 SOIL-ROOT RELATIONS Summary of Program Moisture stress imposes limitations on crop production throughout the Western Hemisphere . Since movement of moisture through soils in unsaturated flow is generally too slow to meet the requirements of rapidly transpiring plants, the development of deep and active root systems is one important means of alleviating moisture stress. Research effort should therefore be focused on developing information that will permit the synthesis of management practices for improving crop rooting depth of important species of each region. Also, there is need for definition of optimum rooting volume for production of important crop species under the various soil and climatic conditions encountered. More specifically, it will be necessary to study the mechanisms by which some plants {including many native species) are able to over- come soil and climatic conditions that are unfavorable for root growth of most cultivated species. One facet of this problem is suggested below. Specific Problems Specific problems and the research teams that will be concerned with them are named below. Persons whose affiliations are not given may be identified by referring to Appendix B. Tolerance for toxicities induced by soil acidity Team: F. Quevedo, E. Bornemisza, and R. w. Pearson; 0. Crocomo, Universidade de S~o Paulo, Piracicaba, Brazil {In addition, M. Blasco, Faculdad de Agronomia del Valle, Palmira, Colombia, should be asked to join in this effort.) Soil-water relations and aeration L. H. Stolzy and w. R. Gardner; w. Forsythe, Institute Inter- americana de Ciencias Agricolas de la Oea, Turrialba, Costa Rica; L. Chang, Estacion Experimental, La Molina, Lima, Peru; K. Reichardt, Universidade de Sao Paulo, Piracicaba, Brazil
28 Nutrient requirements H. P. Haag, Universidade de Sao Paulo, Piracicaba, Brazil; z. F. Lund, University of Alabama, Auburn (The following should be asked to join in this effort: J. Estrada, Universidad Agraria, La Molina, Lima, Peru; C. Labanauskas, University of California, Riverside; M. Blasco L., Faculdad de Agronomia del Valle, Palmira, Colombia.) Soil strength and mechanical impedence L. H. Stolzy; w. Forsythe, Institute Interamericano de Ciencias Agricolas de la Oea, Turrialba; H. Taylor, University of Alabama, Auburn; L. Chang, La Molina, Lima, Peru Training and Exchange Exchange of research personnel engaged in the projects referred to above is recommended. Such exchange would enable workers to become familiar with different environments and would probably lead to widening the scope of work performed. It is also suggested that graduate training related to projects undertaken by the research teams be made available in educational in- stitutions where it is not already available. Institutions cooperating in this program should encourage thesis work.
