No abstract

The pericarp of the Feizixiao lychee (Lychee chinensis Sonn.) remains green when the concentration of sugar in the aril peaks, the so-called stay-green phenomenon. The objective of the present study was to evaluate the effect of foliar-applied Mg on pericarp colour, and to determine the relationship between pericarp colour, plant growth substances, and activities of the key enzymes associated with colour development. We quantified the pigment concentrations and endogenous plant growth substances (abscisic acid -ABA -and ethylene), and determined the activities of chlorophyllase (Chlase), pheophorbide acid monooxygenase (PaO), and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT). Magnesium was found to increase the accumulation of anthocyanin in the pericarp, and contributed to the red colour of the pericarp and overcame the stay-green phenomenon. In contrast, Mg had no effect on the concentration of chlorophyll in the pericarp. Strong relationships between anthocyanin, UFGT, and ABA suggest that the enzyme increased the accumulation of anthocyanin by increasing the concentration of ABA and the activity of UFGT. Strong negative relationships between chlorophyll, PaO and Chlase, and ethylene production suggest that ethylene increased the degradation of chlorophyll by increasing the activity of the two enzymes. The Mg spray was suggested for application in lychee orchards.

Chlorophytum capense var. medio-pictum is widely used as a houseplant with its central yellowish white stripe in green leaves. This study investigated chlorophyll biosynthesis, and epidermal characteristics in leaf stripes of different color. The results showed that yellowish white leaf stripes (YS) have a lower 5-aminolevulinic acid (ALA) content than that of green stripes. Meanwhile, YS had higher coproporphyrinogen III (Coprogen III) and Mg-protoporphyrin monomethyl ester (Mpe) contents, but the lower content of protoporphyrinogen IX (Proto IX) and protochlorophyllide (Pchlide) compared to green stripes, suggesting that the occurrence of yellowish white stripes may be attributed to the blocked ALA synthesis and the inhibited conversions from Coprogen III to Proto IX and Mpe to Pchlide. In addition, the upper and lower epidermal cells in YS were larger than those in green stripes. The chloroplasts developed normally in the guard cells of the YS epidermis, though almost no chloroplasts were detected in YS mesophyll cells.