Guttation in rice : occurence, regulation, and significance in varietal improvement

Guttation is a physiological phenomenon resulting in oozing of drops of xylem sap on the tips or edges of leaves of some vascular plants. Of 11 species belonging to different botanical families, only rice (Oryza sativa L.) was found to guttate heavily. Therefore, the process of guttation in rice was studied in depth. Guttation was found to occur from margins, tips, adaxial and abaxial surfaces of leaves. It was the leaf margins that exuded most (151 μl), followed by adaxial surface (135 μl), and tips (98 μl), in that order. Further, the “ridged” portions exuded more fluid than “smooth” portions of the same leaf blade. The rate of guttation was 132 μl at anthesis, 120 μl at tillering, 112 μl at heading and milky stages, and 42 μl at dough stage. The wind velocity and soil moisture stress, as external factors, played dominant roles in the regulation of guttation. Genotypic variability existed for guttation among six cultivars, with cv. NDRH-2 registering the highest value of 110 μl and Mahsuri the lowest (62 μl). The guttational rates exhibited by various cultivars were positively correlated with their panicle weights, i.e., the yield sink capacity, which may be used as a selection criterion for breeding for enhanced yield. These findings on various aspects of guttation in rice are novel. The information should be useful to breeders for creating a new efficient rice plant having altered genetic makeup for increased guttation for yield improvement.