Chilling effects during maize tassel development and the lack of compensational plasticity
Stress during tassel formation can reduce tassel size and cause insufficient pollen production in seed production. When stresses affect plant development, component compensation for grain yield is known to occur in some crops. Tassel component compensation for pollen production has not been previously reported. Chilling was imposed on two dent maize (Zea mays L.) inbreds (103 and 113 relative maturity [RM]) at the initiation of tassel formation, a critical period for maximizing pollen production. The 103 RM inbred showed limited response to chilling stress. The 113 RM inbred produced 60% fewer branches resulting in 45% fewer spikelets and 43% fewer pollen grains per tassel when chilling was applied during branch meristem initiation. For the same inbred, 42% fewer spikelets and 29% fewer pollen grains per tassel were produced when chilling was applied during spikelet meristem initiation. Chilling stress during meiosis of microsporogenesis did not decrease pollen production per anther. A decrease in the percentage of starch-filled pollen grains was found only in the lower florets on the lowest branch. The effect of decreased branch or spikelet production on total pollen production was not compensated by subsequent production of spikelets, florets, anthers, or pollen grains per anther. Susceptibility of pollen production to chilling stress during tassel formation varies among modern dent inbreds, although plasticity in the tassel for pollen yield was not observed.