Chapter 31 Plant reproduction and growth

Plant growth Fig 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 growth Fig 31.7

Secondary Growth Fig 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 log Fig 31.8B

Anatomy of a log Heartwood; xylem plugged with resins, acts as an endoskeleton Sapwood; secondary xylem that conducts water

Sexual lifecycle in Angiosperms Fig 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 Seed Fig 31.11

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

Seed Structure Fig 31.11

Seed Germination Previously developing embryo starts again after dormancy Seed takes up water, expands, ruptures its coat, stored nutrients are broken down and fuel growth

Fruit Development Fig 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 Primary wall (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(shorter and broader) form a system of tubes for water transport Figure 31.5E Pits Vessel element Tracheids Pits Openings in 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 plate Companion cell Cytoplasm Primary wall

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