Protochlorophyll(ide) forms in hypocotyls of dark‐grown bean (Phaseolus vulgaris)

Abstract

The protochlorophyll(ide) forms and plastid ultrastructure were investigated in hypocotyls of dark‐grown seedlings of kidney bean (Phaseolus vulgaris L. cv. Brede zonder draad). By deconvolution of the fluorescence emission spectra into Gaussian components three protochlorophyll(ide) forms were found with maxima at 633, 642 and 657 nm, respectively. The ratio of protochlorophyll(ide) emitting at 657 nm to protochlorophyll(ide) emitting at 633 nm decreased downwards the hypocotyl. The gradient was established already after 4 days in dark‐grown Phaseolus and was also seen in hypocotyls of 7‐day‐old dark‐grown plants of 8 other species. Ultrastructural observations revealed a plastid developmental sequence along the hypocotyl. Plastids in the upper parts of the hypocotyl contained prolamellar bodies typical of etiolated leaves while those in the lower parts contained only stroma lamellae. Immunological detection of NADPH‐protochlorophyllide oxidoreductase (EC 1.3.1.33) on nitrocellulose membranes after sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDSPAGE) indicated the occurrence of the enzyme in upper, middle and lower sections of hypocotyls and in the root tips.

Transformation of plastids in soil‐shaded lowermost hypocotyl segments of bean (Phaseolus vulgaris) during a 60‐day cultivation period

“…The spectra of the 4‐day‐old hypocotyls (Fig. ) were very similar to those of the etiolated hypocotyls (McEwen et al ). The result of the Gaussian resolution showed somewhat different components: instead of the 642 nm band (McEwen et al ), we found a component at 644 nm that is common in etiolated leaves (Böddi et al ) and small, 0.5 nm differences in the positions of the 631 and 656 nm components.…”

“…) and plastid ultrastructure (Fig. ) to those developed in artificial darkness (McEwen et al ). A similar phenomenon was observed in soil‐shaded pea epicotyls (Vitányi et al ).…”

“…A similar phenomenon was observed in soil‐shaded pea epicotyls (Vitányi et al ). However, the morphology of the etiolated bean hypocotyl is basically different: it was 24 cm long in 7‐day‐old dark‐grown laboratory plants (McEwen et al ) and only 5–7 cm long in the soil‐ and light‐grown 35‐ and 60‐day‐old plants. Also the pigment contents were strikingly different; while the lowermost segment of the etiolated hypocotyls contained only 0.004 nmol Pchl(ide) pigments per gram fresh weight (McEwen et al ), the same segment of soil‐grown plants had several order higher pigment content (Table ).…”

“…The germinating seeds are fully shaded by the soil in the first phase of germination, and similarly to other dark‐grown angiosperm organs, the hypocotyls (and all other organs) show etiolation symptoms. Such symptoms have been described and analyzed in laboratory‐grown etiolated bean seedlings earlier, for example the presence of protochlorophyllide (Pchlide) and protochlorophyll (Pchl), the appearance of etioplasts with prolamellar bodies (PLB) and prothylakoids (PT) were described (McEwen et al ). The 655 nm emitting Pchlide form and its flash‐photoactivity are present; however, the majority of Pchlide and Pchl are built into short‐wavelength emitting forms (McEwen et al ).…”

“…Such symptoms have been described and analyzed in laboratory‐grown etiolated bean seedlings earlier, for example the presence of protochlorophyllide (Pchlide) and protochlorophyll (Pchl), the appearance of etioplasts with prolamellar bodies (PLB) and prothylakoids (PT) were described (McEwen et al ). The 655 nm emitting Pchlide form and its flash‐photoactivity are present; however, the majority of Pchlide and Pchl are built into short‐wavelength emitting forms (McEwen et al ). External δ‐aminolevulinic acid treatment stimulates Pchlide and Pchl accumulation in the hypocotyl (Virgin and McEwen ) similarly to etiolated bean leaves (Gassman ).…”