Overgrowth of Douglas fir (Pseudotsuga menziesii Franco) stumps with regenerative tissue as an example of cell ordering and tissue reorganization

Abstract

Main conclusionStump overgrowth may serve as a unique model for studying cellular reorganization and mechanisms responsible for cell polarity changes during the process of vascular tissue differentiation from initially unorganized parenchymatous cells.Cellular ordering and tissue reorganization during the overgrowth process of the transverse surfaces of Douglas fir stumps in forest stand was studied. At the beginning of stump overgrowth, the produced parenchymatous cells form an unorganized tissue. Particular parenchyma cells start arranging into more ordered structures which resemble rays. Application of digital image analysis software based on structure tensor was used. The analysis showed that at this stage of tissue development, cellular elements display a wide range of angular orientation values and attain very low coherency coefficients. The progress of the tissue differentiation process is associated with the formation of local regions with tracheids oriented circularly around the rays. This coincides with an increase in the range of angular orientations and greater values of coherency coefficients. At the most advanced stage of tissue development, with tracheids arranged parallelly in longitudinal strands, the degree of cell ordering is the highest what is manifested by the greatest values attained by coherency coefficients, and the narrow range of angular orientations. It is suggested that the ray-like structures could act as organizing centers in the morphogenetic field responsible for differentiation of the overgrowth tissue. The circular pattern of tracheids around rays in the initial phase of tissue development can be interpreted in terms of local rotation of the morphogenetic field which afterward is transformed into irrotational field. This transformation is noted by the presence of tracheids arranged parallelly in longitudinal strands. The possible involvement of a mechanism controlling cell polarity with respect to auxin transport is discussed.

Proliferation of axial parenchymatic xylem cells is a key step in wound closure of girdled stems in Pinus canariensis

“…Malformation and disorganization of tracheids in woundwood, as well as the later recovery of a normal pattern has been recently described in fire scars in different conifers [ 22 ] or in mechanical injuries in the stem of Pinus sylvestris [ 42 ] or even in overgrown stumps of felled Pseudotsuga menziensii [ 60 ]. This disorganized xylem, with an increased proportion of resin ducts and associated parenchyma imply an evident disadvantage for the circulation of water and nutrients through the traumatic xylem [ 22 ].…”

Ordering of the cellular arrangement and xylogenesis in wounded shoots of willow

“…It has recently been shown that this technique may be useful for the evaluation of cellular pattern ordering during morphogenetic processes in plants. the method was successfully applied to pattern analysis and cellular ordering in the area where tissues were regenerating after longitudinal stem wounding of adult Scots pine trees (Zajączkowska 2014a) and during the overgrowth process of transverse surfaces of Douglas fir stumps (Zajączkowska 2014b).…”

Xylogenesis in response to severe traumatism in the Canary Island pine (Pinus canariensis C. Sm. ex DC)

“…In these regions, also tangential resin ducts are developed, perpendicular both to axial and radial canals. Malformation and disorganization of tracheids in woundwood, as well as the later recovery of a normal pattern has been recently described in beetle and fire scars in different conifers (Arbellay et al 2014(Arbellay et al , 2017 or in mechanical injuries in the stem of Pinus sylvestris (Zajaczkowska 2014a) or even in overgrown stumps of felled Pseudotsuga menziensii (Zajaczkowska 2014b).…”

“…Traumatic wood usually presents malformed tracheary elements and fibers, with altered lignification patterns, and with a high proportion of parenchymatic cells. Orientation of these elements is also very often distorted (Zajaczkowska 2014a, 2014b, Arbellay et al 2014, Chano et al 2015, probably due to altered hormonal flux, and also to altered mechanical signals, as suggested in Chapter 2 (Chano et al 2015). This disorganized xylem implies an evident disadvantage for water and nutrient transport (Arbellay et al 2014).…”

“…or in mechanical injuries in the stem of Pinus sylvestris(Zajaczkowska 2014a), or even in overgrown stumps of felled Pseudotsuga menziensii(Zajaczkowska 2014b). This disorganized xylem, with an increased proportion of resin ducts and associated parenchyma imply an evident disadvantage for the circulation of water and nutrients through the traumatic xylem(Arbellay et al 2014).…”