Larson D W
Dept. of Botany and Genetics, University of Guelph, NIG 2W1, Guelph, Ontario, Canada.
Oecologia. 1982 Oct;55(1):102-107. doi: 10.1007/BF00386723.
The heat sensitivity of net CO exchange in four Umbilicaria species has been examined. Plants were exposed to pulses of heat from 2 to 24 h, were exposed either air-dry or saturated with water, and then were examined repeatedly under stress-free conditions to see if the responses were stable over many days or weeks. The initial responses found were maintained in all cases up to one month implying that the effects were not reversible. Hydrated plants were much more sensitive than dry plants, but in both cases the sensitivity increased with exposure time. All species showed basically the same critical temperatures thus suggesting that selection in the field was not operating on the basis of differential heat sensitivity. This idea was supported both by observations of thallus temperatures in the field during periods of hot weather, and by observations of thallus temperatures exposed to controlled high temperatures. Both approaches suggested that temperatures high enough to induce heat stress in the field, do not occur.
对四种脐衣属物种净二氧化碳交换的热敏感性进行了研究。将植物暴露于2至24小时的热脉冲中，使其处于风干或水饱和状态，然后在无胁迫条件下反复检查，以观察这些反应在数天或数周内是否稳定。最初发现的反应在所有情况下都能维持长达一个月，这意味着这些影响是不可逆的。含水植物比干燥植物更敏感，但在两种情况下，敏感性都随暴露时间增加。所有物种都表现出基本相同的临界温度，因此表明在野外的选择并非基于不同的热敏感性。这一观点得到了炎热天气期间野外叶状体温度观测结果以及暴露于受控高温下的叶状体温度观测结果的支持。两种方法都表明，在野外不会出现高到足以诱导热胁迫的温度。
