Relationship of Photosynthetic Rate and Edaphic Factors to Root Carbohydrate Trends in Honey Mesquite

Abstract

Total nonstructural carbohydrate (TNC) concentration in honey mesquite (Prosopis glandulosa var. glandulosa) roots and its relation to current photosynthetic rate and selected soil parameters were examined on 2 upland soils. Root carbohydrate recharge rates were generally greater in trees on a sandy loam site than those on a clay loam site during the spring rainy season because of higher photosynthetic rates and more apparent root growth. Recharge rate was greater on the clay loam site during midsummer, which was related to higher soil water potential. Root carbohydrate recharge was less sensitive to a moderate water stress (dawn xylem water potential ranged from -1 to -1.6 Mpa) than was photosynthesis; but it was more sensitive to severe water stress (dawn xylem water potential ranged from -1.9 to 2.4 MPa) than was photosynthesis. Effective control of honey mesquite with foliar-applied herbicides is determined by photosynthetic rates and TNC trends as they are influenced by both soil temperature and soil water content. Higher photosynthetic rates and greater amounts of root TNC are related to higher soil temperature and higher soil water content.