No abstract

Photosynthetic and respiratory rates of developing pods and fully expanded leaves of mesquite were assayed during 1972 to determine whether current photosynthesis was sufficient to supply the demands of the developing pods or whether reserve carbohydrates from the roots were required. Net photosynthetic rates of developing pods were very low when expressed as a function of dry weight, whereas the rates of CO, evolution were high, suggesting a very active metabolic rate. Leaf photosynthetic rates were comparable to reported rates for other tree species. From the data collected, it was concluded that current photosynthate could not supply the amount of organic matter needed for pod development on trees possessing heavy fruiting loads, and reserve carbohydrates would be needed during the period of maximum rate of dry matter accumulation by the pods. Mesquite trees in various phenological conditions respond erratically to foliarapplied herbicides such as the phenoxy acids (Tschirley and Hull, 1958; Fisher, Meadors and Behrens, 1956). These particular herbicides are known to be translocated in the assimilate stream of the phloem (Baidiei, Basler and Santelmann, 1966; Leonard and Crafts, 1956). Therefore, the photosynthate must be actively moving downward in order for sufficient herbicide to reach the root meristem to result in total plant death (Fisher et al., 1956; Dahl et al., 1971). Recent studies by Wilson (R. T. Wilson, unpublished MS thesis, 1972) suggested that mesquite trees possessing many elongating or maturing pods had a lower concentration of total available carbohydrates in the roots than did trees with relatively few or no pods. Whether the root carbohydrates were translocated upward for pod production or whether the decrease in concentration was due to some other factor, was not determined. Previous work, however, indicates that tree species depend on stored carbohydrates to varying degrees for fruit The authors are former research assistant, Range and Wildlife Management Department; assistant professor, Agronomy Department; and associate professor, Range and Wildlife Management Department, respectively,

Cultures of Nitzschia palea were grown in a modified Chu 10 medium over a pH range from 4.0 to 9.9.No growth occurred at pH 4.7 or below, but there was increased cell yield at pH 6.4 to 9.9. Cell yield of the diatoms at pH 7 was less than at pH 8.2. Diatoms did not survive in strongly buffered media at 5.0 g/l or above, but did grow in media buffered at 0.63 g/l or less. Nitzschia palea appears to be alkaliphilous.