Landscape performance and water-deficit stress physiology of birch genotypes (Betula L.)

Twenty birch genotypes (Betula L.) were planted in the field in April 2002, to evaluate their landscape performance at Fayetteville and Hope, Arkansas, and to evaluate their response to two irrigation regimes at Fayetteville. After four growing seasons evaluation of tree survival and growth, B. nigra 'Cully', B. x 'Royal Frost', B. pendula, B. nigra 'BNMTF', B. davurica, and B. papyrifera were possibly adapted for landscape in the Mid-south US in the absence of other limitations. Betula pendula 'Trost's Dwarf', B. ermand, B. albosinensis, B. populifolia 'Whitespire', B. papyrifera 'Uenci', B. lenta, B. maximowicziana, B. utilis var. jacquemontii , and B. alleghaniensis would not be recommended. Water-deficit stress reduced growth in tree height and trunk diameter of birch trees.; Light and [CO2] photosynthetic responses were evaluated on B. nigra 'Cully', B. papyrifera, B. alleghaniensis, and B. davurica under controlled conditions. The light saturation point at 350 ppm [CO2] varied from 743 to 1576 mumol photon m -2s-1, and the CO2 saturation point at 1300 mumol photon m-2s-1 PPFD varied from 767 to 1251 ppm. Water deficit significantly reduced light saturation point at 350 ppm [CO 2] in B. papyrifera, but increased CO2 saturation point at 1300 mumol photon m-2s-1 PPFD.; When the four birch genotypes were exposed to five-week water deficit under controlled conditions, three of the four genotypes (except B. papyrifera) expressed three stages of photosynthetic response: (1) a stress stage, (2) an acclimation stage, and (3) an adapted (or tolerance) stage. The stages were characterized by decreasing, increasing and stabilized Pnws/ww [net photosynthesis presented as a ratio of water-stressed plants to well-watered plants], respectively. A strong relationship between Pn and gs observed in the water-deficit-stressed plants suggested inhibition of Pn by stomatal closure. Leaf tissue was analyzed for osmotic solutes (carbohydrates, polyols, organic acids and mineral nutrients) at the end of the experiment, and no osmotic adjustment was observed. A significant increase in leaf abscission in the water-stressed plants of B. papyrifera compared to the other genotypes could be a morphological adaptation to water deficit conditions and facilitate recovery of Pnws/ww during the acclimation stage.; Exposing B. papyrifera to 20 ppm ethylene resulted in more than 50% leaf abscission after 96 h regardless of plant water status under controlled conditions. One ppm 1-methylcyclopropene or 0.1 mM silver thiosulfate did not affect predawn water potential, gas exchange and chlorophyll fluorescence. A significant increase in ethylene production was not detected in water-stressed plants prior to the onset of significant leaf abscission. Based on these observations, ethylene would appear to play a minor role in water-deficit-induced leaf abscission in B. papyrifera.; From 2003 to 2005, Japanese beetle (Popilla japonica Newman) feeding damage was rated based on leaf skeletonization on birch trees at Fayetteville. During that time, Betula utilis var. jacquemontii, B. papyrifera 'Uenci', and B. papyrifera had severe damage. Betula maximowicziana, B. nigra 'Cully', B. papyrifera 'Renci', and B. platyphylla 'Fargo' had moderate damage. Betula pendula 'Laciniata' did not have noticeable damage. The other birch genotypes in the study had low damage.