Identification of Organic Substances Associated with Tissue Senescence in Upland Cotton (Gossypium spp. L.) Based on GC-MS Analysis

Premature senescence in crop production, especially occurred at the late growth stage, generally results in a reduction in yield and quality. Therefore, it is beneficial for yield and quality to properly delay senescence of plant tissues during the late developmental stage. In this study, it was observed that the chlorophyll content and photosynthetic rate were gradually decreased along leaf growth progression, and the rates of reduction were promoted by drought. Based on gas chromatography-mass spectrometry (GC-MS) analysis, total eight, five, seven, and five kinds of organic compounds that putatively associated with the tissue senescent progression were identified in leaves, fruit branches, petals, and sepals, respectively. It was found that the identified organic compound, such as a-pinene, β-pinene, and pentadecane were present in different tissues. Among the total ten organic substances identified to be related with the leaf senescence, half were specifically detected in the drought treatment. These results suggest some biochemical pathways associated with the leaf senescence are distinctly regulated by drought. The identified organic compounds in the tested tissues showed three types on the performance pattern based on the contents along with the senescent progression, including gradually increasing, decreasing, and a curve with one single peak. Thus, during the senescence process in tissues, a subset of metabolic substances occur modifications on the quantities, reflecting a complicate biochemical reactions are initiated via the senescence signals. Further analysis of the important organic substances will be helpful for elucidation of the tissue senescence mechanism at the biochemical level and provide a new insight of the senescence signaling transductions in cotton.