Hydraulic Conductivity of the Hemp Stems Under Water Stress

Author(s): Mehmet Yuksel, Hadi A. Al-agele, Lloyd Nackley, Chad W. Higgins

The hydraulic conductivity of hemp stems under water-stress conditions was investigated to assess the impact on water transport from the root to the leaves. Water-stress conditions induce embolism (cavitation) in xylem channels, thereby affecting water flow. The percentage loss of water transfer ability within the xylem channels can be represented by a 19 'vulnerability curve' (VC). This study utilized an air injection technique to induce embolisms in the stem and measured the subsequent changes in hydraulic conductivity using a specialized measurement apparatus. The results revealed that the shape of the vulnerability curve for hemp was influenced by the xylem area, which is an atypical finding with no prior evidence in other plant species. The statistical analysis confirmed the significance of this effect (p-value=0.003 at 95% confidence intervals). Consequently, a non-traditional mathematical equation (simple power law) was developed to describe the relationship between pressure and xylem area. Furthermore, our findings demonstrated that hemp stems are more responsive to water stress compared to other plant species documented in previous literature. The minimum pressure (0.15 MPa) at which initial cavitation is observed and the maximum pressure (~2.4 MPa) at which all stem conductance is lost were among the lowest reported values, indicating that hemp growth may be significantly affected by deficit irrigation strategies. Thus, careful monitoring of the irrigation schedule is crucial, particularly for younger stems with smaller xylem cross-sectional areas. These insights into the hydraulic behavior of hemp can contribute to the development of improved irrigation strategies in agriculture, ultimately enhancing water-use efficiency and optimizing crop production.

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