Plant Diversity

Question 1

General features of plants

Answer 1

Photo chrome, cellulose cell wall, plastids, amino acid lysine, haploid and diploid phases

Question 2

The three types of life cycles you could have

Answer 2

Life cycle 1 which involves Zygote undergoing mitosis to for unicellular diploid phase called sporophyte. This undergoes meiosis to form spores and these enter the haploid multicellular phase called the gametophyte which goes onto form gametes through mitosis. The life cycle 2 forms multicellular diploid phase and life cycle 3 involves zygote to multicellular diploid phase and then meiosis to form gametes.

Question 3

How did the landflora originate?

Answer 3

The mother gametophyte has oogamy. The zygote is retained, it develops into sporophyte. The sporophyte emerges and becomes cute used. The spore dispersal leads to four lineages including land plants.

Question 4

What is the advantage of the sporophyte phase

Answer 4

The sporophyte phase means more spores, more meiosis means more genetic variation and more spores means more gametophytes and gametes.

Question 5

What do phragmoplast and plasmodesmata mean?

Answer 5

Phragmoplast is the collection of micro tubules that form between dividing cell. The cell plate forms and a wall allows cells to divide. Plasmodesmata are strands of cytoplasm that connect neighbouring cells.

Question 6

Talk about spore dispersal in mosses and liverworts, ferns and horsetails

Answer 6

Mosses have peristome teeth and liverworts have elaters. The ferns have bent sporangium spine and the horsetails have elaters too.

Question 7

How did seed plants form?

Answer 7

Heterospory and reduction of gametophyte size. So two types of spores are formed, mega spores from megasporangium so the female gametophyte is developed and micro spores from microsporangium to form the male gametophyte eventually. Micro spores are retained in microsporangium and endosporic development.the micro gametophyte enclosed in a pollen wall is called a pollen grain. The mega gametophyte is contained with the megasporangium. The megasporangium has an outer covering called the in tegument. An integumentary megasporangium is called the ovule. Pollination leads to transfer of sperm to ovule.

Question 8

Talk about different vascular tissues

Answer 8

Protostele is a single strand of xylem surrounded by phloem. Eustele is bundles of vascular tissue and siphonostele is interruptions to vascular tissue by leaves.

Question 9

Talk about the synapomorphies and success of angiosperms

Answer 9

Xylem, tectate micro spore wall, double fertilisation,flower, carpel and fruit
Coevolution, biochemical defended and fruit dispersal

Question 10

Draw the gametophyte (female) and mention double fertilisation.

Answer 10

Eight nuclei and seven cells so antipodal, polar synergic and egg cell. Double fertilisation is when sperm fertilises egg cell and the polar nuclei to form triploid endosperm. Faster germination and seedling grown. The development of seed after fertilisation is fruit.

Question 11

What do the terms nucellus, synergid, embryo sac, outer integument, carpel and stamen mean?

Answer 11

Nucellus means megasporangium, embryo sac means megagametophyte, outer Integument is seed fern cupule and carpel defined as subtending the outer Integument, the stamen is branch of seed fern with microsporangia, synergid means archegonium.

Question 12

Briefly describe the classification from green plants to the vascular and non vascular

Answer 12

Green plants, land plants and stone worts. Stone worts have plasmodesmata and phragmoplasts. The land plants are divided into vascular and non vascular. Non vascular plants are called bryophyte and include liverworts, misses and hornworts. Then the vascular plants include seed and seedless plants so seed plants are angiosperms and gymnosperms. The seedless plants are the lycopodiopsida and pteropsida, which are the club mosses and quillworts, and secondly the ferns and horsetails respectively.

Question 13

Define growth and development in plants

Answer 13

Growth is irreversible increase in size and development is increase in tissues and organs accompanied by differentiation

Question 14

How does animal and plant growth and embryogenesis differ?

Answer 14

Plants have unlimited growth, they do not have cell migration in embryos, lack maturity since hey do not have true adult organs in the embryo and the rate and plane of cell division as well as direction of expansion impacts shape of the embryo

Question 15

Talk about body plan of plants and define pattern formation

Answer 15

So plants have apical and basal axis with shoot apical meristem and root apical meristem. There are three types of tissues in plants and the repeating unit of a plant is called a phytogeography, consisting of stem, bud and leaf. Pattern formation is part of embryogenesis and is the arrangement of tissues and cells in three dimensions to form the body plan. The embryo has the hypocotyl and radicle as well as cotyledons.

Question 16

Define meristem, fascination and the roles of tissues in the stem and root. What tissues do the shoot apical and root apical meristems produce, so the specific names.

Answer 16

The meristem is a restricted region of a plant organ in which cell division for growth occurs. Fascination is when you get uncontrolled growth of the meristem and so you get an elongated meristem. Meristem size control is done by plasmodesmata. Then you have dermal tissue in roots that protects them and mediates interactions with the environment. You have vascular tissue for xylem and phloem as well as connecting organs. The ground tissue is neither vascular or dermal. In stems, you have the dermal tissue that goes to form epidermis, the vascular tissue for xylem and phloem as well as parenchyma cells which are types of ground tissue that form the cortex and pith. The cortex contains plastids that store starch. Sam and ram produce pro cambium, which is vascular tissue, protoderm which is dermal tissue and ground tissue.

Question 17

What are the differences between animal and plant hormones.

Answer 17

Animal hormones produced in glands, not plant hormones which have multiple sites of synthesis. Animal hormones very specific but plant hormones not, and plant hormones act locally as well as at a distance, animal hormones at a distance

Question 18

Roles of the five major plant hormones

Answer 18

Auxins for apical dominance, lateral root initiation and cell expansion, gibberellns for cell elongation, flowering and seed germination, en cytokinins for shoot organogenesis, cell division and leaf senescence, absiscic acid is for seed or embryo dormancy and stomata, ethylene is for fruit ripening, leaf abscission, and flowering senescence

Question 19

What is etiolation and de-etiolation?

Answer 19

Etiolation is growth of a plant to reach light when short of food reserves, happens in low light levels and is characterised by apical hook, pale colour, longer hypocotyl and reduced leaf expansion. The other happens in short bursts of light and is a type of growth. It occurs through the photoreceptor phytochrome.

Question 20

How does phytochrome lead to deetiolation. Mention the active and inactive form as well as changes in the cytosol.

Answer 20

So phytochrome exists in active form Pfr and inactive form Pr. When in light, red causes active form to be made, which then increases cytosolic calcium and that leads to cgmp production that activates pk and Tfs to lead to expression of rubisco and chlorophyll a and b. This causes greening response.

Question 21

Talk about factors affecting flowering and photoperiodism in detail. Also explain how flowering occurs in terms of detection and signalling.

Answer 21

Age light and temperature. Photoperiodism is when light causes physiological changes in plant. So in terms of light you have short day plants that flower during night and long day plants that flower during the day. Day neutral plants flower regardless of night length. So what happens is that for short day plants, far red light is higher and so you get the inactive form of phytochrome produced. Low active form of phytochrome detected which stimulates flowering. If there is a red light break at night then you get inhibition of flowering because active form is higher in levels. For a long day plant, Pr is changed to Pfr and this stimulates flowering. You get low degradation of Pfr to Pr. Red light break at night induces flowering as prevention of Pfr degradation. The leaf detects light and this can be proven through bagging and grafting experiments. Bagging experiments you cover the leaf and no flowering. Grafting you take short day induced leaf and graft onto long day uninduced leaf, you get signal from leaf to shoot apex and flowering. The signal is florigen, which changes gene expression at the shoot apex and stimulates flowering from shoot apical meristem. Florigen gene is called flowering locus t.