Heat Stress as a Special Purpose Alternative to Clipping in Alfalfa1

Abstract

AbstractRegrowth in alfalfa (Medicago sativa L.) usually is studied following cutting. The possibility that regrowth after a different type of defoliation might reveal useful information led to the present greenhouse and chamber study. By exposing plants for 5 or 6 hours to heat reaching 52 C, aerial tissues were killed but crown buds survived to regrow. The heat‐stressed plants were delayed from 7 to 14 days in attaining the shoot numbers of clipped plants, but this regrowth appeared morphologically normal and initially was not influenced by the living residual leaf or buds found on stems below a cutting height. Certain attributes of regrowth, following high temperature exposure may prove useful in future research. When plants 50 to 92 days of age received the same stress, the older plants produced shoots in regrowth more rapidly than did the younger. Within an age group, those plants in flower when stressed produced more shoots than did those not yet showing flower buds when stressed. Individual plants with larger shoot numbers before either clipping or heat stress produced more shoots during regrowth.