Chapter 31

Plant reproduction and growth

Plant growthFig 31.7

Plant growth

• Plants have indeterminate growth• Annuals, biennials, periannials• Meristems

– Apical; grows at tips of shoots and roots• Gives rise to cortex, epidermis, and vascular tissues

• Primary growth lenghtens shoots and roots• Secondary Growth (from cambium)

Primary growthFig 31.7

Secondary GrowthFig 31.8A

Secondary Growth

• Increases girth of woody plants– Meristems that grow laterally– Vascular cambium; develops from parenchyma

between xylem and phloem– Outer layers (older) slough off as bark– Cork cambium; produces layers of cork that

protect the plant

Anatomy of a logFig 31.8B

Anatomy of a log

• Heartwood; xylem plugged with resins, acts as an endoskeleton

• Sapwood; secondary xylem that conducts water

Sexual lifecycle in AngiospermsFig 31.9

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Sexual lifecycle in Angiosperms

• Flowers; compressed shoots with modified leaves– Sepals; green, protect flowers– Petals; colorful, attract pollinators– stamens; male, have anthers at tip, deliver

pollen– carpels+ female, stigma, style ,ovule bear

ovules– What is pollination?

• Monocots and eudicots differ in seed leaf number and in the structure of roots, stems, leaves, and flowers

Angiosperms

Ovule to SeedFig 31.11

Seed development

• Triploid cell- develops into endosperm• Zygote develops into embryo• Ovule coat develops into the seed coat

Seed StructureFig 31.11

Seed Germination31.13

Previously developing embryo starts again after dormancy

Seed takes up water, expands, ruptures its coat, stored nutrients are broken down and fuel growth

Fruit DevelopmentFig 31.12

Fruits

• Houses, protects, disperses seeds• Types of fruits

– Simple; pea pod (single carpel and ovary)

– Aggregate; blackberry (many carpels)– Multiple; pineapple (many flowers)

Plant Cells

• Two part cell wall• Stiff secondary cell wall• Middle lamellae• Plasmodesmata

31.5 Plant cells and tissues are diverse in structure and function

Figure 31.5A

• There are five major types of plant cells– Parenchyma– Collenchyma– Sclerenchyma– Water-conducting cells– Food-conducting cells

• Parenchyma cells function in food storage, photosynthesis, and aerobic respiration

• Thin primary cell walls

Figure 31.5B

Primarywall(thin)

Pit

• Collenchyma cells provide support in parts of the plant that are still growing

• Unevenly thickened primary cell walls

Figure 31.5C

• Sclerenchyma cells provide a rigid scaffold that supports the plant

– Rigid secondary cell walls (Lignin)

– Fiber cells– Sclerid cells

Figure 31.5D

– Sclereids (stone cells) (gritty pear)

• Water-conducting cells convey water from the roots to the stems and leaves

– Chains of tracheids (long w/tapered ends) or vessel elements(shorterand broader) form a system of tubes for water transport

Figure 31.5E

Pits

Vessel element

Tracheids

Pits

Openingsin end wall

• Food-conducting cells function in the transport of sugars, other compounds, and some mineral ions

– Sieve-tube members are arranged end-to-end, forming tubes

– Their end walls are perforated with plasmodesmata, forming sieve plates

– At least one companion cell flanks each sieve-tube member

Figure 31.5F

Sieve plateCompanioncell

CytoplasmPrimarywall

• Complex tissues are composed of more than one type of plant cell

• Vascular tissues are complex tissues that conduct water and food – Xylem contains water-conducting cells that convey

water and dissolved minerals – Phloem contains sieve-tube members that transport

sugars