Growth, nutrient allocation and water relations of mesquite ( Prosopis chilensis) seedlings at differing fertilization schedules

Abstract

Effects of contrasting fertilization schedules on biomass and nutrient partitioning between different plant organs, and the water relations of Prosopis (mesquite) seedlings were studied in the greenhouse over a 13 week rotation to assess nutritional preconditioning to short term drought. The seedlings received 200 mg N per plant as complete nutrient solution during the growing season supplied either conventionally (as single dose or repeated top dressings) or exponentially (as pure or modified exponentially increasing additions). Although mode of fertilization did not influence total dry matter production of the seedlings, biomass and nutrient distribution between different plant organs were affected. Proportionally more biomass was allocated to the leaf components in exponentially than conventionally fertilized plants. This trend was reversed, however, in root growth as relatively more dry matter was distributed to the roots in conventional than exponential fertilization schedules. Despite stems accounting for about half of the total plant dry mass, relative macronutrient contents in the stems were lower as most nutrients were allocated to the leaves. On the other hand, phosphorus concentration in the roots was higher than in leaves of conventionally fertilized seedlings. At the end of the rotation, exponentially fertilized and well-irrigated seedlings exhibited higher stomatal conductance and transpiration throughout the course of a single day. Induced drought, however, decreased both diurnal stomatal conductance and transpiration. On the same day, drought also altered diurnal patterns as all the treatments were the same except for the single dose fertilized plants which maintained higher stomatal opening and transpiration.