Morphology and Water Relations of Leaves of Eucalyptus grobulus Sprouts

Characteristics of leaf inorphology and water relations were examined and compared for the leaves of Eucnlyfil'us grobztlus which shows continuous changes of leaf form from oval in the current sprouts to lanceolate in the normally grown shoots. With the changes of leaf form, several anatomical features were observed to change continuously. The normal leaves had long petioles and showed some 'sun leaf' characteristics, i. e., three or four layers of ~nesophyll palisade cells, srnall specific leaf area, dense venation, and low air space ratio. On the other hand, the current sprout leaves si~owed the 'shade leaf' characteristics. On the abaxial surface of the current sprout leaves, snlaller stomata in high frequency compared to those of norrnal leaves were observed. No stomata was observed on the adaxial surface of the sprouts leaves although there was about a frequency of 60% of abaxial stomata in the i1ormal leaves. Water relation parameters obtained by the pressure-volume curve technique suggested that the sprout leaves were inferior in maintaining cell turgor against water loss compared to the i~orinal leaves. Under field conditions, transpiration rates and stoi~~atai conductances were higher in the sprout leaves, while leaf water potelltials were almost the same in both the sprout and the 11or111al leaves. Tlle leaf specific coi1ductai~ce of tree bole supporting unit leaf area, calculated from the relationship between leaf water potentials and transpiration rates, was higher in sprouts. It was collcluded that the sprout leaves, which have a lower-light efficient morphology and a smaller contellt of osn~otic water, nlaiiltain the high stoll~atal col1ductance supported by a high leaf specific conductance.