Hypertrophied Lenticels Research Articles

Photosynthetic and Growth Responses of Silver Maple (Acer saccharinum L.) Seedlings to Flooding

Flooding affected several growth parameters of silver maple (Acer saccharinum L.) seedlings. Root biomass and leaf area were sharply reduced. Photosynthetic rates of recently germinated seedlings decreased significantly after 21 days of root-flooding and after only 3 days of submersion. In some treatments, reduced net photosynthesis/transpiration ratios after flooding indicated a decline in water use efficiency. Seedlings submersed in water containing suspended sediments had lower rates of photosynthesis than plants submersed in clear water. The timing of flooding treatments (spring vs. late summer) had no apparent effect on the pattern of decline in net photosynthesis. Two-year-old seedlings had a greater capacity for net photosynthesis after flooding than recently germinated seedlings, suggesting that recovery of normal physiological function after flooding is an important survival feature of older silver maple seedlings. Light conditions had minimal effect on seedling growth and photosynthesis. Seedlings had relatively high rates of photosynthesis over a broad range of photosynthetically active photon flux density and developed a shade leaf' morphology when grown at low light intensity. Duration of flooding is the most important characteristic of the flood cycle affecting the survival and establishment of silver maple seedlings in floodplain habitats. INTRODUCTION Silver maple (Acer saccharinum L.) is widely distributed throughout the eastern United States. It occurs chiefly on floodplains and on the moist sites of creek bottoms, and is the dominant species in many floodplain communities in the Midwest (Bell, 1974; Franz and Bazzaz, 1977). Silver maple develops best in well-drained, moist soils (Fowells, 1965), and is extremely tolerant of flooding (Hosner, 1960; Teskey and Hinckley, 1977b). Seedlings experience periodic flooding which normally occurs during spring or summer in the Midwest. Furthermore, floodwaters vary considerably in their sediment and nutrient loads, especially in watersheds that drain agricultural fields (Peterson and Rolfe, 1982b). It is critical that silver maple and other bottomland species have the ability to withstand periodic flooding. Excess water in flooded soils displaces air from the pore space, and the resulting poor aeration increases root resistance to water uptake (Kramer and Kozlowski, 1979). An early physiological response to flooding is stomatal closure (Regehr et al., 1975; Pereira and Kozlowski, 1977), which prevents loss of leaf turgor in the absence of water uptake. Some species develop adventitious roots and hypertrophied lenticels in response to prolonged flooding (Keeley, 1979), and stomata reopen as water uptake is initiated (Kozlowski and Pallardy, 1979). Additional environmental factors, such as night temperature, have been shown to affect stomatal resistance and net photosynthesis in some bottomland tree species (Drew and Bazzaz, 1979). The present study was initiated to determine growth and physiological responses of silver maple seedlings to flooding. Patterns of net photosynthesis and transpiration were measured for seedlings subjected to root-flooding and total submersion. Both 1 Present address: U.S. Forest Service, Riverside Fire Laboratory, 4955 Canyon Crest Drive, Riverside, California 92507.

Ethylene production and morphological adaptation of woody plants to flooding

Seedlings of Ulmus americana, Fraxinus pennsylvanica, Melaleuca quinquenervia, and Eucalyptus camaldulensis exhibited greater morphological adaptation to flooding than did Eucalyptus globulus or Pinus halepensis seedlings. Formation of hypertrophied lenticels and production of adventitious roots on submerged portions of stems were characteristic of the flood-tolerant species only. Ethylene production was greatly stimulated by the flooding of all species except P. halepensis. In flooded F. pennsylvanica seedlings ethylene production was higher in stems with well-developed hypertrophy than in those without stem hypertrophy. Lack of a vertical gradient in ethylene content of the stems of flooded Eucalyptus plants indicated either that waterlogging of soil indirectly stimulated ethylene production in stems above the waterline or that ethylene was translocated upward from submerged portions of stems. Application of indoleacetic acid stimulated ethylene producton in submerged portions of M. quinquenervia and U. americana stems. The data indicate an important role for ethylene in the morphological adaptation of woody plants to flooding. The additional involvement of several other compounds in such adaptation is discussed.

Water relations, ethylene production, and morphological adaptation ofFraxinus pennsylvanica seedlings to flooding

Fraxinus pennsylvanica Marsh. seedlings that were 150 days old adapted well to flooding of soil with stagnant water for 28 days. Early stomatal closure, followed by reopening as well as hypertrophy of lenticels and formation of adventitious roots on submerged portions of stems appeared to be important adaptations for flood tolerance. Leaf water potential (ψ1) was consistently higher in flooded than in unflooded seedlings, indicating higher leaf turgidity in the former. This was the result of (1) early reduction in transpiration associated with stomatal closure, and (2) subsequently increased absorption of water by the newly-formed adventitious roots as stomata reopened and transpiration increased. Waterlogging of soil was followed by large increases in ethylene content of stems, both below and above the level of submersion. Formation of hypertrophied lenticels and adventitious roots on flooded plants was correlated with increased ethylene production. However, the involvement of various compounds other than ethylene in inducing morphological changes in flooded plants is also emphasized.

Leaf Conductance, Growth, and Survival of Willow and Deciduous Fruit Tree Species under Flooded Soil Conditions

Abstract Potted seedlings and cuttings of various tree species were submerged to 5–10 cm above the soil level for up to 20 months in order to determine flood tolerance based on leaf conductance (kl), growth, and survival. Flooding induced a decline in kl at soil oxygen diffusion rates of 30, 22, 20, and 15 × 10−8g cm−2 min−1 for Prunus persica (L.) Batsch, Halford seedlings (peach), Pyrus communis L. cv. Bartlett (Bart), Pyrus calleryana Decne (Call), and Pyrus betulaefolia Bunge (Bet), respectively. The leaves of some species, particularly Pyrus communis L. cv. Old Home × Farmingdale 97 (OH × F 97), abscised shortly after a decline in kl, yet leaves of most other Pyrus species did not abscise despite months of maintaining a kl near zero. Growth rates were reduced for all fruit tree species except Bet and Call after one month of spring flooding. One month of fall flooding reduced the growth of all fruit tree species the following spring. Bet survived 20 months of continuous submergence; however, only Salix discolor Muhl. (willow) grew well under these conditions. Flooding promoted adventitious rooting of willow, Cydonia oblonga Mill. cv. Provence BA 29 (quince) and Malus domestica Borkh. cv. MM 106 (apple); anthocyanin pigmentation in leaves of apple and all Pyrus species; leaf chlorosis of quince, apple, and peach; and hypertrophied lenticels on the submerged stems and roots of all species. The tolerance, based upon kl, growth, and survival, was: willow > Bet > Call = quince > Bart > OH × F 97 = Pyrus pyrifolia (Burm.) Nak. (Pyri) = Pyrus ussuriensis Maxim. (Ussuri) = apple > peach. Although the survival of pear rootstocks with and without a ‘Bartlett’ scion were similar, flooding symptoms often were quite different.

Flooding and SO2 Stress Interaction in Betula papyrifera and B. nigra Seedlings

The effects of flooding of soil for 5 weeks and fumigation of shoots with 0.35 ppm SO/sub 2/ for 30 hours, alone and in combination, were studied on Betula papyrifera Marsh. (paper birch) and Betula nigra L. (river birch) seedlings. B. papyrifera, an upland species, was adversely affected by flooding more severely than B. nigra, a lowland species. Symptoms of flooding injury in both species included stomatal closure, chlorosis, deterioration of root systems, and greatly reduced dry matter accumulation. Flooding induced formation of hypertrophied lenticels and adventitious roots in B. nigra but not B. papyrifera seedlings. Seedlings of both species recovered 1 to 2 wk after flooding ended and continued growing at a faster rate than unflooded seedlings, thereby partially or completely compensating for the growth-inhibiting effects of flooding. Fumigation with SO/sub 2/ at the end of the flooding period induced partial stomatal closure, injury to leaves, and reductions in mean relative growth rates in both species. Stomatal conductance and SO/sub 2/ uptake in B. nigra seedlings were reduced 40 to 45 percent by flooding, respectively, and consequently SO/sub 2/ caused less visible injury (17 vs. 44 percent of leaf area) and less growth inhibition (0 vs. 26 percent inmore » mean relative root growth rate) in flooded than in unflooded seedlings. Stomatal conductance and SO/sub 2/ uptake were reduced even more in flooded B. papyrifera (75 and 77 percent, respectively), yet flooded and unflooded seedlings were similarly affected by SO/sub 2/. Flooding stress apparently affected mechanisms of pollution avoidance and pollution tolerance differently in the two species.« less

Responses of Ulmus americana seedlings to flooding of soil

Flooding of soil induced several physiological, morphological, and growth changes in 12- or 13-week-old Ulmus americana L. seedlings. Among the early responses to flooding was stomatal closure, without subsequent reopening, in leaves that were fully expanded by the time flooding was initiated. However, flooding did not induce stomatal closure of leaves that completed expansion during the flooding period. Flooding greatly accelerated production of ethylene by stems. Other responses to flooding included stem swelling; production of hypertrophied lenticels and abundant adventitious roots on submerged portions of the stem; reduction in leaf formation and expansion; and inhibition of dry weight increment of leaves, stems, and roots. Some of the morphological responses to flooding appeared to be associated with accelerated ethylene production. The much greater reduction in root growth over leaf growth in flooded seedlings will create leaf water deficits and predispose seedlings to drought injury after the flood waters recede.

Physiological, morphological, and growth responses ofPlatanus occidentalis seedlings to flooding

Flooding ofPlatanus occidentalis L. seedlings for up to 40 days induced several changes including early stomatal closure, greatly accelerated ethylene production by stems, formation of hypertrophied lenticels and adventitious roots on submerged portions of stems, and marked growth inhibition. Poor adaptation ofPlatanus occidentalis seedlings to soil inundation was shown in stomatal closure during the entire flooding period, inhibition of root elongation and branching, and death of roots. Some adaptation to flooding was indicated by (1) production of hypertrophied lenticels which may assist in exchange of dissolved gases in flood water and in release of toxic compounds, and (2) production of adventitious roots on stems which may increase absorption of water. These adaptations appeared to be associated with greatly stimulated ethylene production in stems of flooded plants. The greater reduction of root growth over shoot growth in flooded seedlings will result in decreased drought tolerance after the flood waters recede. The generally low tolerance to flooding of seedlings of species that are widely rated as highly flood tolerant is emphasized.

Some physiological and morphological responses of Quercusmacrocarpa seedlings to flooding

Flooding for 30 days induced several changes in Quercusmacrocarpa Michx. seedlings, with stomatal closure among the earliest responses. Stomata remained more closed in flooded than in unflooded plants during the entire experimental period. Leaf water potential was consistently higher in flooded than in unflooded plants. Other responses to flooding included acceleration of ethylene production by stems; formation of hypertrophied lenticels on submerged portions of stems; growth inhibition, with greatest reduction in roots; and formation of a few adventitious roots on submerged portions of the stem above the soil line. Some of the morphological responses to flooding, especially formation of hypertrophied lenticels, appeared to be associated with increased ethylene production. Quercusmacrocarpa seedlings adapted poorly to flooding as shown by failure of stomata to reopen after an early period of flooding and low capacity for production of adventitious roots. The much greater inhibition of root growth than shoot growth by flooding will reduce drought tolerance after floodwaters recede.

Growth Responses and Adaptations of Fraxinus pennsylvanica Seedlings to Flooding

Flooding induced several physiological and morphological changes in Fraxinus pennsylvanica seedlings, with stomatal closure among the earliest responses. Subsequent changes included: reduction in dry weight increment of roots, stems, and leaves; formation of hypertrophied lenticels and production of adventitious roots on submerged portions of the stem above the soil line; leaf necrosis; and leaf abscission. After 15 days of stomatal closure as a result of flooding, stomata began to reopen progressively until stomatal aperture was similar in flooded and unflooded plants. Adventitious roots began to form at about the time stomatal reopening began. As more adventitious roots formed, elongated, and branched, the stomata opened further. The formation of adventitious roots was an important adaptation for flooding tolerance as shown by the high efficiency of adventitious roots in absorption of water and in high correlation between the production of adventitious roots and stomatal reopening.

Ethylene Effects on Apple Scions1

Abstract Dormant apple scions stored in plastic bags with ripening apples at room temperature for 7-14 days show severe swelling and bark splitting due to callus proliferation at the apical end as well as general lenticel hypertrophy (intumescence). This apparent ethylene effect can be duplicated by soaking scions in (2-chloroethyl)phosphonic acid (ethephon) at 1000 ppm for 5 or 40 minutes. One-year-old stems cut into three 20 cm sections show the effect at the apical end of the middle and basal sections, indicating the ethylene-induced injury in related to wounding and that the effect is polar and not necessarily associated with differences in cambial activity that may occur along a stem. Some callus proliferatiomay occur at the basal end of scion pieces if the cut at the basal end is made through a bud. Removal of a ring of bark along the stem of a scion piece does not affect the ethylene-induced injury on the cut apical end but bark swelling may occur at the basal portion of the girdle. Bud excision tends to increase the severity of apical injury to scion pieces.