Abstract
The assessment of plant water status under drought conditions is essential for the understanding of the adaptation physiological mechanisms of plants, because water stress is one of the most common limitations of crop growth and yield. This study was carried out to estimate the leaf water content in sunflower plants based on spectral reflectance in the near-infrared region. Two varieties of sunflower plants were cultivated during two autumn seasons inside a non-acclimatized greenhouse until the start of the flowering stage, and later were maintained in a growth chamber with the purpose of submitting the plants to a slow and progressive dehydration rate during 12 consecutive days. Measurements of spectral reflectance and leaf mass (fresh and dry) were accomplished along the water stress period. Increases on the spectral reflectance values were observed as the leaf water loss was intensified. The coefficients of determination (R2) of models between leaf water content (LWC) and water index (WI) were 0.948 and 0.956 for Sunbright and Sunbright Supreme varieties, respectively, while the R2 between LWC and wavelength where the first-order derivative of the spectral reflectance is minimum (λdmin) were 0.979 and 0.988 for Sunbright and Sunbright Supreme varieties, respectively. Based on the results, the radiometric indicators (WI andλdmin) might be useful tools in the development of automatic systems, resulting in a non-destructive, simple, easy, and instantaneous method for monitoring water status in sunflower plants.
