mention four characteristics of sunflower's vascular bundles
The vascular bundles are typically collateral and open ones, with xylem and phloem on the same radius, xylem being internal and phloem external. A strip of lateral meristem, cambium, is present between xylem and phloem.
The xylem is characteristically endarch, showing centrifugal mode of differentiation from the procambium. The protoxylem elements, tracheids and tracheae, with smaller cavities and annular and spiral thickenings occur towards the centre; and the metaxylem elements with pitted and other types of thickenings are present towards the circumference.
Xylem parenchyma cells are smaller than other parenchyma cells of the stele. The phloem is composed of sieve tubes, companion cells and phloem parenchyma. The cambium of the vascular bundle, what is called fascicular (fascicle =bundle), appears to be composed of two or three layers of fusiform cells, which look rectangular in cross- section. This tissue is responsible for growth in thickness. this is the common characters for dicotyledons and sunflower comes under dicotyledons.
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