The development of blackcurrant fruit from flower to maturity: a comparative study by 3D nuclear magnetic resonance (NMR) micro-imaging and conventional histology
Sm. Glidewell et al., The development of blackcurrant fruit from flower to maturity: a comparative study by 3D nuclear magnetic resonance (NMR) micro-imaging and conventional histology, NEW PHYTOL, 141(1), 1999, pp. 85-98
The development of fruits of blackcurrant (Ribes nigrum) cv. Ben Alder from
flower to maturity was studied non-invasively by nuclear magnetic resonanc
e (NMR) microscopy, using attached and detached fruits, and the images were
compared with those from low temperature scanning electron microscopy (LTS
EM) and conventional resin histology. The NMR images derived from 2-D and 3
-D datasets showed the previously unreported growth of arillar tissues to t
he extent that they almost completely occlude the locular cavity, but LTSEM
and resin histology revealed that no fusion occurs between the arillar tis
sues and the gelatinous sheath surrounding each seed, or between the arilla
r tissues and the endocarp. The discontinuities between these tissues cause
magnetic inhomogenities which result in these structures being clearly res
olved by gradient echo imaging sequences. During seed maturation the endosp
erm changed from high (bright) to low (dark) signal intensity as lipid rese
rves formed and solidified, whereas the gelatinous sheath had high signal i
ntensity throughout maturation. The high lipid concentration in the seed wa
s manifested by chemical shift effects in the images and the increasing vis
cosity of the endosperm was reflected in the decrease in spin-lattice (T-1)
relaxation times. The funiculi, throughout development of seeds, appeared
in NMR images with low signal intensity and 3-D surface-rendered reconstruc
tions illustrated the complexity of the spatial array of seeds and funiculi
arising from parietal placentas within the loculus. All other vascular tis
sues in the pericarp and placentas were resolved as a small bright core sur
rounded by a dark region, within a matrix of moderate signal intensity. Con
ventional microscopical studies then showed that the bright core discernibl
e by NMR imaging encompassed an entire vascular bundle whereas the darker s
urrounding region represented small parenchyma cells with pronounced interc
ellular gas spaces. Other regions of the pericarp which included extremely
large parenchyma cells, however, had fen intercellular spaces and consequen
tly gave rise to brighter regions of the image.