Relationship Between Weathering Deterioration and Germination, Respiratory Metabolism, and Mineral Leaching from Cottonseeds¹

Abstract

Germination of cottonseeds ( Gossypiura hirsutum L.) is reduced by preharvest exposure to,weather, particularly if conditions are warm and humid. To identify some of the germination processes affected by weathering deterioration, seedlots of six cultivars were harvested before and after a period of field exposure and comparative germination studies were conducted. Seedling field emergence was reduced by 11 to 33% due to weathering. During imbibition, weathered seeds of sensitive cultivars released more K + , Mn 2+ , Mg 2+ , and Ca 2+ , but less Na + into the steep solution than did their unweathered counterparts. Leaching of individual minerals was a better indicator of seed quality than was the total release of electrolytes; release of K + Ca 2+ than was significantly correlated with measurementosf seed quality. Respiratory O 2 uptake was reduced in deteriorated seeds, with elevated estimates of the RQ after 7.5 h of imbibition. Aeration with 100% O 2 increased O 2 uptake and reduced the RQ, indicating that O 2 diffusion may have limited respiration during early germination. Weathering deterioration of membranes was confirmed by electron microscopy of cotyledonary lipid and protein bodies. Thesed ata indicate that the loss of membrane functional integrity is a major factor responsible for the reduction of germination potential by weathered seeds, and that the release of K + and Ca 2+ into steep water during imbibition may be a good indicator of cottonseed planting quality.