do monocots undergo secondary growth? how do you account for greater size reached by some monocots?

Answer 1

Secondary growth in monocots is one of Botany's best kept secrets! Monocots that exhibit secondary growth do not show much internodal elongation. Coconut palms (niu) and Pandanus (hala) are good examples. If you look carefully at their stems you can see that there is little distance between successive leaf scars and the leaves are tightly assembled at the top of the tree. You will also note that older parts of the stem have Periderm. The stems of these plants tend to have a uniform diameter from top to bottom because most of the increase in girth takes place close to the apex.
If you examine the shoot apex of some monocots you will see that the shoot apical meristem is normal but the leaf primordia are inserted in close order with virtually no separating internodes.
A broad sub-apical meristem that exhibits Periclinal cell divisions underlies the leaf primordia. This is the Primary Thickening Meristem (PTM). It adds layers of cells towards the base of the stem and thus contributes somewhat to its height. Cell enlargement at the periphery of the PTM also causes the stem to increase in diameter close to the apex. Primary vascular tissues differentiate within the derivatives of the PTM and connect the leaves to the vascular bundles of the stem.
In some plants the PTM is continuous around the flanks of the stem and extends to its base. The continuation of the PTM is called the Secondary Thickening Meristem (STM). Cell divisions in the STM are largely periclinal and produce most new cells towards the interior of the stem. Vascular bundles and parenchyma differentiate within the derivatives of the STM and they add to the diameter of the stem as they enlarge. This can result in a stem with a wide base. Is that clear!! Yes Drill Sargent!!
Hawaiian ki (Cordyline) has both a Primary Thickening Meristem and a Secondary Thickening Meristem. Banana (mai'a) has a Primary Thickening Meristem but lacks a Secondary Thickening Meristem.

Answer 2

Prakash is right ... secondary growth in monocots is not well known. It is often called dracaenoid growth because it was described early on from the Dragon's Blood tree, Dracaena draco. It is important to distinguish between true secondary thickening and mere expansion of primary tissues. Studies have shown that some palms, at least, grow extremely slowly at first because they spend a long time establishing a broad vegetative apex ... this is the reason that palms are mostly the same diameter all the way up. True secondary growth mostly means that the plants are thicker at the base than they are at the apex.

Answer 3

Secondary Growth In Monocot Stem

Answer 4

most monocots are actually dicots also. Like trees they are both. this is how they growth but this can be the secondary growth. the monocots use symbosis with a fungas to grow bigger.

Answer 5

I've for gotten some of this stuff, the cots(seed leaves) cotyledons are part of the seed. Seeds can grow into REALLY BIG things. Maybe pine trees. They grow by using photsynthesis to make sugar and the sugar gets fused to make cellulose. Wood.