The mesophyll is dorsiventral, with conspicuous intercellular spaces in the spongy parenchyma.
The disease caused by CABMV was more drastic in P. edulis, resulting in changes in the constitution and organization of vascular bundles of the leaf blade, with irregular arrangement of xylem and phloem elements, as well as spongy parenchyma cell hypertrophy.
The ground tissue system, the mesophyll, is divided into two regions: the palisade parenchyma, located beneath the upper epidermis and composed of columnar cells oriented perpendicular to the leaf surface, and spongy parenchyma, located in the lower part of the leaf and composed of irregularly shaped cells.
The spongy parenchyma was usually compact in 65% of the species and loose in the rest.
The palisade parenchyma and spongy parenchyma in the leaf mesophyll are important photosynthetic tissues.
Indeed, in senescing leaves of vernalized plants, large cells were distributed not only in palisade but also in spongy parenchyma.
a, b, c, and d represent the palisade parenchyma while e, f, g, and h the spongy parenchyma.
Single mesophyll cells from Zinnia elegans contain both palisade and spongy parenchyma cells approximately 50 μm long and 25 μm wide.
Palisade parenchyma consisted of three to four layers of regular-shaped cells while spongy parenchyma was characterized by less organized structure.
In addition, whereas intercellular spaces in control plants were observed mainly in spongy parenchyma, these spaces were present in the whole mesophyll of leaves from stressed plants.
Other features, such as the number of palisade parenchyma layers or the spongy parenchyma type (open or compact), were also determined.
