Carbohydrate reserve patterns in honey mesquite during bud-break

Honey mesquite (Prosopis glandulosa var. glandulosa) is a widespread "pest" plant occurring primarily in Texas and other parts of the Southwest. Mesquite growing on the High and Rolling Plains of Texas was sampled during the 1979 and 1980 growing seasons and analyzed for TNC (total nonstructural carbohydrates). Mesquite samples were collected from trees growing on a deep hardland range site on the High Plains and three different range sites (deep hardland, valley and mixedland slopes) in the Rolling Plains to evaluate the effect of soil type on the physiological processes occurring in mesquite. At each sampling date environmental parameters such as soil moisture, soil temperature and air temperature were measured along with a phonological description of each tree sampled. These data were collected to determine if there was a relationship between the environmental parameters and the physiological processes of mesquite. Root, trunk (basal stem), stem (2-year-old growth) twig (previous years growth) and bud samples were collected weekly to determine trends of carbohydrate movement in mesquite during the growing season with particular emphasis on the physiological activity at bud-burst. Mesquite in all plant parts increased in TNC concentration prior to budburst followed by a rapid decrease as plants began to leaf out. Recharge of root carbohydrates began when leaf expansion was near completion and occurred more rapidly than aboveground plant parts. These results indicate that the aboveground storage organs of mesquite are capable of storing and providing energy to emerging buds. The above ground plant parts, particularly stems, twigs and buds, can likely supply energy to growing leaves and flowers more effectively than roots and trunk because of their proximity to the buds. The data from this study confirm root and stem TNC trends reported in other studies and supplement that research by describing physiological activity of buds and twigs at bud-burst.