Effects of water and fertilizer integration on growth, morphology, physiology and photosynthetic characteristics of flue-cured tobacco in the North China

Drought stress inhibits the growth and development of flue-cured tobacco in the North China, resulting in lower yield and quality. The purpose of this study was to determine the effects of integration of water and fertilizer on the growth and development, root morphology and physiology, and on photosynthetic characteristics of flue-cured tobacco in the North China. The differences in agronomic attributes, dry matter accumulation, root morphology and physiology, photosynthesis, chlorophyll fluorescence and economic characteristics of'Yunyan 87'flue-cured tobacco grown under water and fertilizer integration, and conventional irrigation and fertilization were investigated. The results showed that compared with conventional irrigation and fertilization, the growth and development of flue-cured tobacco was significantly promoted under water and fertilizer integration and with better agronomic attributes. The integration of water and fertilizer significantly increased dry matter accumulation in the belowground and aboveground parts of the plant. It also improved the indices for root morphology and physiology in terms of root volume, total root absorption area, root active absorption area, root specific surface area, root activity and ATPase activity. All these attributes were significantly higher than those under conventional irrigation and fertilization. The integration of water and fertilizer also reduced root to shoot ratio (P < 0.05). Meanwhile, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), water use efficiency (WUE), PSⅡ maximal photochemical efficiency (F_v/F_m), PSⅡ actual photochemical efficiency (φ_PSⅡ) and photochemical quenching coefficient (q_P) all significantly increased under the integration of water and fertilizer (P < 0.05). On the contrary, both transpiration rate (T_r) and non-photochemical quenching coefficient (NPQ) significantly decreased under the integration of water and fertilizer (P < 0.05). Furthermore, the economic characteristics were significantly higher under the integration of water and fertilizer than those under conventional irrigation and fertilization (P < 0.05). In conclusion, the results indicated that the integration of water and fertilizer supported good root morphology and significantly improved root physiology activity, photosynthesis and light energy utilization efficiency. This stimulated the growth and development of flue-cured tobacco, resulting in higher economic characteristics.