Studies on the effects of mutagens on cultured cells of higher plants II : Radiosensitivity in callus tissues of Phaseolus vulgaris L. cv. Kentucky Wonder (Agriculture)

菜豆(Phaseolus vulgaris L. cv. Kentucky Wonder)のカルス, 幼苗および種子に対するγ線照射の影響を比較した。照射カルスの生長は線量の増加に伴って有意な減少を示したが抑制程度は一様ではなく, 初期から生長が認められた2.5∿5KR, 生長遅延を示したが生長を続けた6.25∿8.75KRおよびほとんど生長が認められなかった10KR以上のほぼ3群に大別された。照射カルスの継代能力は12.5KR以上ではほとんど認められなかった。カルスは線量の増加に伴って褐色の度合およびもろさの程度が増加した。一方, 幼苗照射における生長抑制は, 1KRでは約50%で頂端分裂組織も正常であったが, 2KRでは顕著な抑制と頂端分裂組織の脱落が認められ, 5KR以上では枯死した。また, 種子照射においては, 10KRまでは約30%の抑制であったが, 20KR以上ではほとんど生長が認められなかった。以上の結果から, 生長抑制でみた菜豆のカルス, 幼苗および種子の放射線感受性には顕著な差異が認められた。すなわち, 幼苗が最も感受性で, 種子が抵抗性であり, カルスはほぼその中間であった。
A comparative study on the effects of ^(Co) gamma radiation was carried out on callus tissue, seedlings and seeds of Phaseolus vulgaris L. cv. Kentucky Wonder. Callus was obtained from the hypocotyl pieces grown on an agar-solidified, modified Linsmaier and Skoog's medium supplemented with 2,4-D (5mg/1), kinetin (5mg/1) and yeast extract (1,000mg/1). Subculture was conducted on the same medium in the dark at 28±1℃. Callus was exposed to various doses (2.5-15KR) of gamma radiation at 20KR/hr. Fresh and dry weight, potency of growth in subculture of irradiated callus, color and friability were measured. As compared with control, irradiated callus growth showed a significant decrease with increasing doses. Callus growth was classified into three types, i.e. callus began to grow from the early stage of culture at 5KR and below, from 6.25-8.75KR there was a delayed growth, at 10KR and over there was little visual sign of growth. The potency of growth in subculture for 28 days of irradiated- and 24-day-cultured callus was recognized at 10KR and below. With increasing doses, color of callus darkened, and the degree of friability increased. While 10-day-old seedlings were irradiated, striking inhibition of growth occurred at 2KR, followed by degradation of the apical meristem and growth ceased completely at 5KR. Severe inhibition of growth of irradiated seeds occurred at 20KR and over. A remarkable difference in radiosensitivity was observed among callus tissue, seedlings and seeds, i.e. seedlings were most sensitive, followed by callus tissue, and seeds were most resistant.