SURVIVAL AND RECOVERY OF MEYER ZOYSIAGRASS RHIZOMES AFTER EXTRACELLULAR FREEZING

Rhizomes of 'Meyer' zoysiagrass (Zoysiajaponica Steud.) were subjected to temperatures below 0 degrees C and were subsequently placed in a g rowth chamber with air at 34 degrees C day/28 degrees C night to deter mine the rate of shoot growth from nodes. Rhizomes exposed to subzero temperatures produced shoots steadily up to 16 days after freezing (DA F), but subsequent shoot growth from rhizomes was minimal. At 32 DAF, shoots were present on 68% and 44% of the nodes of unfrozen control (2 degrees C) rhizomes and those frozen to -7 degrees C, respectively. I n another study, samples were frozen to a sublethal temperature (-7 de grees C) to examine the distribution of extracellular ice voids near t he apical meristems of rhizomes and to characterize tissue recovery. E xtracellular voids were present within the leaf tissue and between the leaves in samples prepared for scanning electron microscopy (SEM) imm ediately after freezing to -7 degrees C. By 12 DAF, most of the remain ing voids were observed in older leaves. Nearly all extracellular void s in the leaves were absent by 20 DAF, However, by 28 DAF, some rhizom es still had small voids between leaves. Although the structure of zoy siagrass rhizomes subjected to -7 degrees C was temporarily disrupted, tissues recovered from extracellular freezing and new shoot growth wa s produced following exposure to warm temperatures.