Pumpkin stem. Light micrograph of a section through phloem sieve tubes in the stem of a pumpkin (Cucurbita pepo) plant. Each sieve tube element consists of cytoplasm along the cell wall and a central vacuole,containing slime-bodies (light green),and no nucleus. The top sieve tubes shows the transverse layer of cellulose,which is perforated by holes (red),known as the sieve plate,through which the slime flows forming a plug (callus). The contents flow up and down taking substances such sucrose (sugar) down to the roots and upwards to the shoot. To left of the phloem is a companion cell full of cytoplasm (dark green) and a nucleus. Magnification: x37 when printed 10 centimetres wide | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Wheeler, Dr. Keith |
Bildgröße: | 3543 px × 5315 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |