Types and structure of budsThe buds include meristems and appendages at the shoot tip and on the nodes (in the leaf axils), the primary structure of the stem, the primary structure of the stem, the three elements of the primary structure of the stem, the epidermis, the cortex, the vascularcylinder or the middle column, the secondary growth and secondary structure of the stem, the stem development of angiosperms reaches a certain stage, and the lateral meristems in the stem begin to divide. The process of thickening the growth and differentiation of the stem is called secondary growthThe secondary tissue produced by the secondary growth becomes the secondary structure of the stemThe secondary meristem of the stem includes: vascular cambium (vascularcambium)—secondary vascular tissue is constantly added to the side, corkcambium—the secondary structure of the stem, which forms the peripheral peribark of the stem, the metamorphosis of the stem(1)The type of aboveground stem, stem spines. Stem tendrils. Leafy stems. Small bulbs (2) Types of underground stemsBulbsSecondary phloemPrimary phloemVascular formationLayersXylemPrimary xylemPlug layerSeasonal activities and growth rings of vascular cambium have significant temperate and subtropical seasons in cold and warm seasons, or tropical in dry and wet seasons, and cambium activities change rhythmically with the change of seasons.

Early wood - the temperate spring or tropical wet season (early growing season), due to the high temperature, sufficient moisture, and vigorous cambium activity, the cells in the secondary xylem formed are large in diameter and thin in the wall; The texture is relatively loose and the color is slightly lighter.

Latewood - in late summer, early autumn or tropical dry season in temperate zones, cambium activity gradually weakens, forming cells with small diameter and thick walls, and often increasing the number of tracheids; The texture is dense and the color is darker.

Growth rings – growth rings, consisting of early and late wood, are secondary xylem that form during the year.

Bark: A broad concept that refers to all tissues other than the vascular cambium layer of the old trunk of the stem, which is the protective structure on the periphery of the trunk.

From the inside out, it includes the phloem, cortex, and periderm that has been formed multiple times, as well as all dead tissue outside of the cork layer.

Vascular cambium wood: This is actually the xylem of the stem. And it's secondary xylem. (It is composed of ducts, tracheids, wood fibers, and wood parenchyma cells, all of which are lignified to varying degrees).

Sapwood, also known as liquid wood, is the part of the secondary xylem with lighter color on the periphery of the heartwood, and it is also the part of the secondary xylem that is relatively new close to the bark, which contains living cells and has the role of transport and storage.

Heartwood - the inner layer, the early secondary xylem, the deeper central part near the stem, nutrients and oxygen are not easy to enter, the tissue undergoes senescence and death, the ducts and tracheids often have lost their conduction effect, and the ducts and tracheids are filled with resin, tannins, oils and other substances to form an invading body.

Structure of monocot stems (1) In general, monocots have only primary structures and no secondary structures.

A few species are special - such as the dracaena tree. With an age of more than 8,000 years, it is the longest-lived tree on Earth and is known as a living fossil among plants.

Dracaena grows unusually slowly, taking hundreds of years to grow into a single tree and only blooming once in decades, so it is very rare.

Although dracaena is a monocot plant, the parenchyma cells in its stem can continue to divide, so that the stem thickens year by year.

Its tree shape is strange and beautiful, and it is very ornamental. It is known as the folk in Yunnan

"Immortal pine" is an auspicious symbol of prolonging life and protecting children and grandchildren (2) The vascular bundles in the stems of monocots are scattered, and do not form vascular columns, and the two arrangements (scattered distribution and two-wheel distribution) are external tough vascular bundles, and they are also finite vascular bundles.

Section 3 General Morphology of StemsMorphology of StemsNode - where leaves are born on the stemInternode - part of the bud between two nodes - Leaf marks (bud) that have not been developedTraces left after defoliationLong branches and short branchesFixed budsAdventitious budsSide budsAxillary budsFlower budsMixed budsNaked budsScaly buds Active budsDormant budsFlower budsMixed budsLeaf budsGrowth habits of stems: *Erect stems - stems grow perpendicular to the ground and erect.

*Wrap the stem – the stem cannot stand upright, and the stem itself is wrapped around other pillars to grow. *Climbing Stem - The stem cannot stand upright, and grows upwards with its unique structure climbing other pillars.

* Stolon - the stem is slender and soft, lying flat on the ground and spreading and growing, and adventitious roots grow downward at the nodes.

* Flat stems - the stems lie flat on the ground and spread and grow, and the nodes do not form adventitious roots. Growth Habits of StemsGrowth Habits of StemsErect StemsWinding StemsClimbing StemsRecumbent StemsStolon Branches—is the form of stem growth, is the result of bud activity, division and growthUniaxial branchingAxial branchingPseudobifurcationTillering of grasses?

Axillary buds and adventitious roots are produced on the tillering joints, and the axillary buds grow rapidly to form branches.

The tillers on the main stem are called primary tillers, and the tillers produced on the primary tillers are called secondary tillers,......?

What segment does tillering occur on which section is it called the tillering position ......? A tiller that can be tasseled and fruitful is called an effective tiller?

A tiller that cannot be tasseled and fruited is called an invalid tiller? The internodes of the wheat stem are extremely short, several nodes are dense at the base, the proportion of the tillers cortex in the stem is small, there is generally no endothelial layer in the stem, and the innermost layer of the stem cortex of some plants is rich in starch, which is called the part within the endothelial layer of the starch sheath vascular column, including multiple vascular bundles, pith and medullary ray vascular bundles, primary xylem primary phloem cambium layer A, external tenatric vascular bundles, most such as sunflower, castor, alfalfa, etc.

B. Bi-tough vascular bundles, such as pumpkin, sweet potato, tomato, oleander, etc. C. Perivascular vascular bundles, mostly seen in ferns, and rarely seen in angiosperms.

D. Zhou Mu vascular bundles, such as cattails, iris, sedges, lily of the valley, etc. Types of primary vascular bundles: Vascular cambium composition: 1. Generation of vascular cambium: a layer of cells with the ability to divide between the primary xylem and the primary phloem develops to form a cambium in the bundle.

The myeloid ray cells that meet the cambium in the fascicle are restored