RESPONSE OF TOMATO TO ELEVATED DAY AND NIGHT TEMPERATURE UNDER CONTROLLED STRESS CONDITIONS

Abstract

Climate change-induced temperature rise pose a significant threat to Tomato (Solanum lycopersicum L.) production by affecting plant growth, physiology, and reproductive development. A pot culture experiment was conducted at the Agro Climate Research Centre, Tamil Nadu Agricultural University, Coimbatore, to assess the effects of Day stress, Night stress, and combined day and night stress (complete stress) across three transplanting windows (D₁ - 6 December, D₂ - 23 December, and D₃ - 6 January). The highest Leaf Area Index (3.25) occurred in the first transplanting under control at 45 days, while the lowest (1.23) occurred in the third transplanting under complete stress at 15 Days after transplanting (DAT). Photosynthetic rate declined from 18.5 to 12.7 µmol CO₂ m⁻² s⁻¹, whereas proline increased from 178.9 to 469.9 µmol g⁻¹ under control and complete stress, respectively. Fertility coefficient decreased from 88% to 63%. Flowers and fruits declined from 32 to 21 and 28 to 15 plant⁻¹, respectively, in the first transplanting, with the lowest values (16 flowers and 10 fruits plant⁻¹) under complete stress in the third transplanting.  Fruit yield declined from 2.5 kg plant⁻¹ under control to 0.8 kg plant⁻¹ under complete stress. The delayed transplanting window exacerbated negative consequences of heat stress. Complete stress significantly reduced tomato growth, physiology, and productivity, while an early transplanting window on 6th December (D₁), which falls under the 49th Standard Meteorological Week, emerged as a potential adaptation strategy to minimise heat-stress impacts under changing climatic conditions.