Effects of Drought and Defoliation on Some Metabolites in Roots of Black Oak Seedlings

Abstract

Starch levels in roots were lower in defoliated, watered black oak seedlings than in non-defoliated, watered seedlings in two separate experiments. Starch levels in unwatered, non-defoliated seedlings were lower only when drought was severe. Drought and defoliation together resulted in lower starch levels than either one alone. Reducing sugars and several amino acids were higher in unwatered seedlings than in nondefoliated and watered ones, but not in those subjected to less severe droughts. Some increase in averages of reducing sugars and certain amino acids occurred in once- and twice-defoliated, watered plants. Levels of catechin and quercitrin were usually lower in defoliated than in nondefoliated seedlings, regardless of watering, and higher in unwatered seedlings than in watered ones, regardless of defoliation. Addition of fertilizer to the soil had no effect on growth, but in some combinations of drought and defoliation it resulted in lower carbohydrate levels.

Factors associated with the decline disease of sugar maple on the Allegheny Plateau

“…Upper slopes are the driest positions in the landscape. Like defoliation, drought has negative effects on accumulation of root starch, although the effects of drought seem to be less than those of defoliation (Parker and Patton 1975).…”

Measuring changes in stress and vitality indicators in limed sugar maple on the Allegheny Plateau in north-central Pennsylvania

“…In stressed trees, starch content reflects the combination of vigor and vitality (ability of an organism to grow and survive in its surroundings; see Shigo 1986). Starch content is a dynamic indicator of stress and shows the effects of defoliation Wargo 1972Wargo , 1981, drought (Parker and Patton 1975), air pollution (Miller et al 1968), and soil acidification (Wargo et al 1993). In urban sugar maples, trees with healthy crowns had high starch content, while those with declining crowns had low or depleted starch (Carroll et al 1983).…”

Consequences of environmental stress on oak: predisposition to pathogens

“…Alanine, asparagine, leucine, and other amino acids increase in the bark and wood of roots of defoliated trees and seedlings (Wargo, 1972;Parker and Patton, 1975;Parker 1979). Asparagine and other amino acids increase in tree seedlings in response to drought (Parker, 1979).…”

“…Alanine and asparagine are (individually) very satisfactory and leucine moderately satisfactory nitrogen sources for growth of Armillaria (Weinhold and Garraway, 1966). The fungus also responds to increases in total amino nitrogen, and defoliation and drought increase the overall level of amino nitrogen in the roots (Parker and Patton, 1975).…”