| A | B |
|---|
| guard cells | paired cells flanking a stoma |
| trichomes | hair like epidermal outgrowths |
| root hairs | single cells found near root tips |
| ground tissue | primarily parenchyma cells |
| parenchyma cells | most abundant cells of primary tissues |
| collenchyma | living at maturity (usually long-lived) |
| sclerenchyma | thick, tough secondary walls |
| lignified | contain lignin |
| lignin | highly branched polymer that reinforces structure |
| fibers | long, slender, usually grouped in strands |
| sclereids | variable in shape; often branched; single or in groups |
| sclereids examples | gritty “stone cells” of pears |
| fiber example | strands of flax, woven to make linen |
| xylem | principle water conducting tissue |
| (transpiration | pulls water upward |
| conducting elements | tracheids and vessels |
| tracheids | taper at ends and overlap one another |
| vessels | continuous hollow tubes (linked row) |
| primary xylem from procambium | (from apical meristem) |
| secondary xylem • from vascular cambium | (from lateral meristem) – can form wood |
