A proposal for universal formulas for estimating leaf water status of herbaceous and woody plants based on spectral reflectance properties

Abstract

The present study deals with the relationships between water status parameters of plant leaves and reflectances (Rλ) at characteristic wavelengths, between 522 and 2450 nm, as well as reflectance ratios, Rλ/R1430, Rλ/R1650, Rλ/R1850, Rλ/R1920, and Rλ/R1950, based on the air-drying experimental results of soybean (Glycine max Merr.), maize (Zea mays L.), tuliptree (Liriodendron tulipifera L.) and viburnum (Viburnum awabuki K. Koch.) plants. The water status parameters include leaf water content per unit leaf area (LWC), specific leaf water content (SWC), leaf moisture percentage of fresh weight (LMP), relative leaf water content (RWC) and relative leaf moisture percentage on fresh weight basis (RMP). Effective spectral reflectances and reflectance ratios for estimating the LWC, SWC, LMP, RWC and RMP were identified. With these spectral indices, approaches to estimating LWC, RWC and RMP were discussed. Eventually, an attempt on universal formulas was made for estimating the leaf moisture conditions of both herbaceous and woody plants as mentioned above. Moreover, applicability of these formulas was checked with the field experimental results of soybean and maize grown under water and nutrient stresses.