Fig 1.
Transverse section of melon lateral branches.
(A) Transverse section of melon lateral branches under normal night temperature conditions; (B) A vascular bundle in lateral branches.
Table 1.
Changes in cell morphology of the phloem ultrastructure of lateral branches of melons after 12 day of low night temperature treatment at 12°C or 9°C when compared with control treatment at 15°C.
Fig 2.
The ultrastructure of phloem in lateral branches of melons before low night temperature treatments.
(A) Overall structure of phloem in lateral branches, ×2000; (B) The major cells of phloem in lateral branches, ×4000; (C) The developed sieve element (SE), developing sieve element and intermediary cells (IC) of phloem in lateral branches, ×58000; (D) The SE ultrastructure of phloem in lateral branches, ×58000; (E) The chloroplasts (CH) in SE of phloem in lateral branches, ×58000; (F) The sieve pores (SP) in SE of phloem in lateral branches, ×58000; (G) The companion cells (CC) of phloem in lateral branches, ×58000; (H) The phloem parenchyma cells (PP) of phloem in lateral branches, ×58000; (I) The phloem parenchyma cells (PP) becoming to sieve element of phloem in lateral branches, ×36000. SE: sieve tube element; CC: companion cells; IC: intermediary cells; PP: parenchyma cells; CH: chloroplast; N: nucleolus; V: vacuoles; P: plastids; M: mitochondria; RER: rough endoplasmic reticulum; P-protein: protein fiber system; SP: sieve plates.
Fig 3.
The ultrastructure of companion cells (CC) of phloem in lateral branches of melons after low night temperature treatments.
(A-F) The CC of phloem in lateral branches of control plants (A and B: ×19000; C, D, E, and F: ×58000); (G-I) The CC of phloem in lateral branches after low night temperature treatment at12°C for 12 d (G and H: ×19000; I: ×58000); (J-L) The CC of phloem in lateral branches after low night temperature treatment at 9°C for 12 d (J and K: ×19000; L: ×58000). SE: sieve tube element; M: mitochondria; RER: rough endoplasmic reticulum.
Fig 4.
The ultrastructure of intermediary cells (IC) of phloem in lateral branches of melons after low night temperature treatments.
(A, B) The IC of phloem in lateral branches of control plants, ×19000; (C) The IC of phloem in lateral branches after low night temperature treatment at 12°C for 12 d, ×19000; (D-F) The IC of phloem in lateral branches after low night temperature treatment at 9°C for 12 d (D: ×29000; E and F: ×19000). CC: companion cells; IC: intermediary cells; SE: sieve tube element; S: starch grain.
Fig 5.
The ultrastructure of parenchyma cells (PP) of phloem in lateral branches of melons after low night temperature treatments.
(A) The PP of phloem in lateral branches of control plants, ×36000; (B, C) The PP of phloem in lateral branches after low night temperature treatment at 12°C for 12 d, ×19000; (D) The PP of phloem in lateral branches after low night temperature treatment at 9°C for 12 d, ×19000; (E) The PP of phloem in lateral branches after low night temperature treatment at 9°C for 12 d, ×58000. PP: parenchyma cells; M: mitochondria; RER: rough endoplasmic reticulum; S: starch grain.
Fig 6.
The raffinose family oligosaccharide (RFO) contents in vascular bundle of lateral branches and carpopodiums of melons after low night temperature treatments for 12 days.
After 12-day treatments at 15°C (control night temperature) or 12°C or 9°C low night temperature, RFO contents were measured in the lateral branches and carpopodiums. Values are the means ±SD of three replicates (with each replicate being a pool of 3 plants); and ** P<0.01 compared to control.