Horticulture Science - Ch 7 - Plant Growth & Development

Growth in plants is defined as an irreversible increase in volume or dry weight (biomass), which includes size increase by cell division and enlargement, as well as the synthesis of new cellular material and organization of subcellular organelles. True or False?

True. Explanation: This is the comprehensive definition of plant growth provided.

Plant development is the progress of a plant through its life cycle, encompassing stages like seed germination, growth of vegetative organs, initiation and maturation of reproductive organs, fertilization, seed development, and senescence and death. True or False?

True. Explanation: This outlines the full scope of plant development.

The thickening of trunks in dicotyledonous trees is primarily due to secondary growth produced by what meristematic region? A) Apical meristem B) Root cap C) Vascular cambium D) Lateral buds

C) Vascular cambium. Explanation: The vascular cambium is responsible for secondary growth, which increases the girth of stems and roots.

The control of gene activity in plant development primarily depends on the cell type, environmental conditions, and the particular stage of development. True or False?

True. Explanation: Gene expression is highly regulated by internal and external factors.

Selective gene activation and deactivation during plant development are mediated mostly through the action of what type of proteins?

Transcription factors. Explanation: Transcription factors bind to DNA and control the transcription of genetic information from DNA to RNA.

Which of the following is NOT explicitly mentioned as a biotic signal that may trigger the action of regulatory genes? A) Plant hormones B) Inorganic ions C) Coenzymes D) Environmental temperature

D) Environmental temperature. Explanation: Plant hormones, inorganic ions, and coenzymes are listed as biotic signals, while temperature is an environmental factor.

The wavelength range commonly referred to as visible light or photosynthetic active radiation (PAR) is: A) 100 to 400 nm B) 380 to 800 nm C) 700 to 1000 nm D) 800 to 1200 nm

B) 380 to 800 nm. Explanation: This is the spectrum of light used by plants for photosynthesis.

A greater proportion of incident sunlight is reflected around sunrise and sunset compared to midday due to a higher angle of incidence. True or False?

True. Explanation: At lower angles of incidence (sunrise/sunset), sunlight is spread over a larger area, leading to more reflection.

Heliotropic movements in plants like sunflowers are primarily used to: A) Maximize water absorption B) Lower the amount of light absorbed to prevent overheating C) Increase photosynthesis by keeping flowers facing the sun D) Both B and C

D) Both B and C. Explanation: These movements can optimize light capture for photosynthesis or reduce light absorption to prevent damage.

Which two specific wavelengths are described as being much more effective in driving photosynthesis than green light?

440 nm (blue light) and 650 nm (red light). Explanation: Plants primarily absorb blue and red light for photosynthesis.

A key distinction between photomorphogenic responses and photosynthesis is that photomorphogenic responses are primarily sensitive to light intensity. True or False?

False. Explanation: Photomorphogenic responses are typically insensitive to light intensity, but sensitive to light quality (spectral composition).

The phytochrome pigment system has two interconvertible forms: a red light-absorbing form and a far-red light-absorbing form. Which form is converted to the far-red absorbing form upon irradiation with red light?

The red light-absorbing form. Explanation: This conversion is central to the phytochrome system's function.

A decline in the Red to Far-Red (R:FR) ratio, often occurring when light penetrates leaf canopies, typically leads to which of the following plant responses? A) Increased branching B) Increased chlorophyll synthesis C) Reduced stem diameters D) Increased height

D) Increased height. Explanation: A low R:FR ratio can signal competition for light, promoting etiolation (stem elongation).

What specific blue light receptor is responsible for phototropism (movement in response to light)?

Phototropin. Explanation: Phototropin is a photoreceptor that mediates phototropism.

The bending in positive phototropic responses is believed to be caused by the accumulation of which plant hormone on the shaded side of the stem, promoting cell expansion?

Auxin. Explanation: Auxin promotes cell elongation on the shaded side, causing the plant to bend towards light.

Some species exhibit a negative phototropic response, meaning they grow towards the light source. True or False?

False. Explanation: A negative phototropic response means growing away from the light source.

The three basic response types for photoperiodically controlled processes are Long-day plants (LDPs), Short-day plants (SDPs), and Day-neutral plants (DNPs). True or False?

True. Explanation: These categories describe how plants respond to day length for flowering and other processes.

For a Long-day plant (LDP), a photoperiodically controlled process is induced when the day length is _ its critical day length. A) Shorter than B) Equal to C) Longer than D) Irrelevant to

C) Longer than. Explanation: LDPs require a period of light longer than a specific critical duration to flower.

The "autumn syndrome" in many woody plants is a collection of integrated processes that include acquisition of freeze tolerance, dormancy of buds, and leaf fall. True or False?

True. Explanation: These are coordinated responses to prepare for winter.

Which of the following common fruit trees is explicitly mentioned as an exception where dormancy and the autumn syndrome are not controlled by photoperiod? A) Peach B) Cherry C) Apple D) Pear

C) Apple. Explanation: Apples and pears are noted as exceptions whose dormancy is not solely photoperiod-controlled.

The critical day length for dormancy induction can vary by several hours among members of a species, especially when individuals from different are compared. A) Cultivars B) Latitudes C) Soil types D) Altitudes

B) Latitudes. Explanation: Plants from different latitudes adapt to different day length cues for dormancy.

Many herbaceous perennials survive winter by forming that are protected by being buried underground. A) Seeds B) Tubers C) Buds D) Spores

B) Tubers. Explanation: Tubers act as storage organs that allow the plant to survive harsh conditions underground.

Most temperate-region plants optimally grow between which temperature range for maximum vegetative growth and flowering? A) 0°C (32°F) and 10°C (50°F) B) 4°C (39°F) and 10°C (50°F) C) 10°C (50°F) and 20°C (68°F) D) 20°C (68°F) and 30°C (86°F)

B) 4°C (39°F) and 10°C (50°F). Explanation: This specific range is given as optimal for many temperate plants.

The term "solarized" or "sunburned" refers to: A) Leaves appearing chlorotic due to low R:FR ratios B) Plants suffering heat damage when exposed to high light intensities C) The process of maximizing light absorption via heliotropic movements D) Leaves changing color in autumn syndrome

B) Plants suffering heat damage when exposed to high light intensities. Explanation: Intense light can convert to heat, damaging plant tissues.

The most common injury from low, nonfreezing temperatures is that ice crystals rupture cell membranes and walls, preventing water flow. True or False?

False. Explanation: Ice crystal formation and rupture occur under freezing temperatures, not low nonfreezing temperatures.

Which of the following is NOT listed as a cold-induced process in the range of 0°F to 10°F? A) Seed germination (stratification) B) Flowering (vernalization) C) Dormancy breakage (chilling requirement) D) Fruit ripening

D) Fruit ripening. Explanation: The other options are examples of developmental processes requiring cold induction.

Stratification refers to the period during which seeds are imbibed at low temperatures, making germination possible. True or False?

True. Explanation: Stratification breaks dormancy in seeds by mimicking natural winter conditions.

With plentiful water, plant cells become , where the plasmalemma presses against the developing cell wall, promoting longitudinal elongation. A) Plasmolyzed B) Flaccid C) Turgid D) Dehydrated

C) Turgid. Explanation: Turgor pressure is essential for cell expansion and growth.

To keep plants short, a strategy mentioned is to withhold water during cell elongation in the stems, known as what process?

Drying down. Explanation: Limiting water can restrict cell expansion and overall plant height.

The two gases most important to the growth of green plants are carbon dioxide (CO2) and what other gas?

Oxygen (O2). Explanation: CO2 is used in photosynthesis, and O2 is used in respiration.

Stomatal opening and closing are regulated in part by leaf CO2 levels and are greatly influenced by photosynthesis. Under what conditions do stomata typically remain open? A) High atmospheric CO2 concentration B) Low atmospheric CO2 concentration and favorable water availability C) Low atmospheric CO2 concentration and water scarcity D) High CO2 and water scarcity

B) Low atmospheric CO2 concentration and favorable water availability. Explanation: Photosynthesis consumes CO2, lowering its internal concentration, which signals stomata to open if water is sufficient.

Which of the following is the correct order of the three main stages of seed germination? A) Increase in biological activity, imbibition, radicle and shoot emergence B) Radicle and shoot emergence, imbibition, increase in biological activity C) Imbibition, increase in biological activity, radicle and shoot emergence D) Imbibition, radicle and shoot emergence, increase in biological activity

C) Imbibition, increase in biological activity, radicle and shoot emergence. Explanation: Water uptake (imbibition) precedes metabolic activation and emergence of the embryo.

Upon emergence, the embryonic root, known as the , quickly becomes a functioning root, making contact with water and nutrients. A) Plumule B) Cotyledon C) Radicle D) Epicotyl

C) Radicle. Explanation: The radicle is the first part of the embryo to emerge from the seed.

Strictly speaking, vegetative growth includes roots, shoots, and leaves, but excludes reproductive structures. True or False?

True. Explanation: Vegetative growth refers to the non-reproductive parts of the plant.

Which of the following is NOT listed as a principal function of roots in higher plants? A) Anchoring plants in the soil B) Absorbing water and mineral nutrients C) Conducting water and organic materials D) Performing photosynthesis

D) Performing photosynthesis. Explanation: Photosynthesis primarily occurs in the leaves and green stems.

The enlarging shoot and root systems maintain a balance, where increased water loss from the shoot is compensated by what?

Increased water absorption from an increasing root system. Explanation: The growth of the root system is proportionate to the water demands of the shoot.

In determinate growth, flower bud clusters form at shoot terminals after a period of vegetative growth, leading to most shoot elongation stopping. True or False?

True. Explanation: Determinate growth results in a finite size as apical meristems convert to floral meristems.

Plants with indeterminate growth bear flower clusters along the stems in the axils of the leaves, and shoot terminals typically remain vegetative. A) Terminally B) Laterally C) Radially D) Basally

B) Laterally. Explanation: Indeterminate growth allows for continuous vegetative growth alongside flowering.

Biennial plants require how many growing seasons to complete their life cycle, though not necessarily two full years?

Two. Explanation: Biennials typically complete their life cycle over two growing seasons, with vegetative growth in the first and reproduction in the second.

For biennial plants like celery and Brussels sprouts, exposure to what environmental condition triggers hormonal changes leading to stem elongation and flowering?

Chilling temperatures. Explanation: Many biennials require a period of cold (vernalization) to induce flowering.

In most annual and biennial plants, what action can often delay senescence?

Continued removal of flowers and fruits. Explanation: Preventing seed production can extend the vegetative phase by delaying the resource reallocation for reproduction.

Woody perennial plants' shoot and root systems remain alive indefinitely, growing to the ultimate size programmed by their gene complement and environment. True or False?

True. Explanation: Perennials can live for many years, with their woody structures allowing for long-term survival.

For temperate trees, growth often occurs , in "flushes," during the growing season. A) Continuously B) Intermittently C) Once a year D) Only in spring

B) Intermittently. Explanation: Growth occurs in bursts (flushes) rather than continuously throughout the season.

A newly germinated seedling undergoes a phasic development throughout its life, including embryonic growth, juvenility, a transition stage, maturity or adult phase, and what final stage?

Senescence and death. Explanation: These stages describe the complete life cycle of a plant.

The juvenile phase in plants is characterized by the inability to: A) Absorb water efficiently B) Perform photosynthesis C) Reproduce sexually D) Form woody tissue

C) Reproduce sexually. Explanation: Juvenility is defined by the inability to flower or produce seeds.

The duration of the juvenile phase can vary from a week or two to as long as thirty or forty years in some tree species. True or False?

True. Explanation: The length of the juvenile phase varies greatly among plant species.

From a practical point of view, juvenility is a serious obstacle in breeding programs for economically important fruit and forest trees. True or False?

True. Explanation: The long juvenile phase can delay breeding efforts for trees.

Juvenile eucalyptus trees have broad, opposite leaves that lack a petiole. How do adult eucalyptus leaves differ?

Adult eucalyptus leaves become alternate, are narrower, and have a distinct petiole. Explanation: This is an example of the morphological changes that occur during phase change.

Juvenile citrus seedlings are thorny. What happens to their thorns after the plant undergoes phase change?

Thorns are no longer produced. Explanation: This morphological characteristic is lost as the plant matures.

Which of the following is NOT listed as a phase involved in fruit and seed production? A) Flower induction and initiation B) Leaf senescence C) Pollination D) Fruit set and seed formation

B) Leaf senescence. Explanation: Leaf senescence is related to aging and nutrient recycling, not a direct phase of fruit and seed formation.

A majority of agricultural plants are self-inductive for flowering, meaning they initiate flowers when they reach a certain what?

Morphological maturity. Explanation: Their flowering is primarily determined by reaching a specific developmental stage rather than external cues.

Growing Degree Days (GDD) are a way to measure what environmental factor?

Heat accumulation. Explanation: GDDs are used to predict plant developmental stages based on temperature.

Which group of plants is described as not being affected by daylength for flowering, including tomato, corn, and cucumber?

Day-neutral plants (DNPs). Explanation: DNPs flower irrespective of the photoperiod.

A flash of light of sufficient intensity or duration, often referred to as a "night break," can inhibit flowering in a short-day plant (long-night plant). True or False?

True. Explanation: Interrupting the dark period prevents SDPs from flowering.

The ability to induce chrysanthemums to flower uniformly year-round is an example of commercial application of photoperiodism, achieved by manipulating light/dark cycles. True or False?

True. Explanation: Growers use blackout cloths to control photoperiod and induce flowering out of season.

Circadian rhythms are biological rhythms that complete one cycle in approximately how many hours?

24 hours. Explanation: These internal clocks regulate daily physiological processes.

The positive signal that promotes photoperiodic flowering, transported via the phloem from exposed leaves to the apical meristem, is called , or the floral stimulus. A) Auxin B) Gibberellin C) Florigen D) Cytokinin

C) Florigen. Explanation: Florigen is the hypothetical signaling molecule that induces flowering.

The CONSTANS gene produces a transcription factor protein that acts as the signal for flowering by turning on which other gene?

FT (flowering locus T) gene. Explanation: CONSTANS activates FT, leading to the floral transition.

Vernalization, the cold temperature treatment that induces or promotes flowering, typically requires temperatures within what range? A) Below 0°C (32°F) B) 0°C (32°F) to 10°C (50°F) C) 10°C (50°F) to 20°C (68°F) D) Above 20°C (68°F)

B) 0°C (32°F) to 10°C (50°F). Explanation: This low temperature range is necessary for vernalization in many plants.

Which of the following plants can be vernalized as seeds? A) Hyacinth B) Tulip C) Beet and Kohlrabi D) Narcissus

C) Beet and Kohlrabi. Explanation: Some plants can perceive the cold stimulus at the seed stage.

What term describes the vegetative growth of axillary buds below an aborted floral apex, which occurs when daylength or temperature conditions are no longer favorable for flower induction?

Bypass growth. Explanation: This occurs when the plant reverts to vegetative growth after an attempt at flowering fails.

Pollination is the transfer of pollen from the anther to the stigma in angiosperms. True or False?

True. Explanation: This is the initial step in sexual reproduction for flowering plants.

A self-sterile plant cannot set fruit and seed with its own pollen, often due to incompatibility where the plant's own pollen will not grow through which structure into its embryo sac?

The style. Explanation: Incompatibility mechanisms can prevent pollen tube growth through the pistil's style.

Besides insects and wind, which of the following are also listed as pollinating agents? A) Snails, slugs, birds, and bats B) Fungi and bacteria C) Water and sunlight D) Soil organisms

A) Snails, slugs, birds, and bats. Explanation: While less common, these animals can also transfer pollen.

In angiosperms, the process where the pollen tube discharges two sperm nuclei (1N each) into the embryo sac is termed what?

Double fertilization. Explanation: This unique process involves one sperm fertilizing the egg and the other fusing with the central cell.

The elapsed time between pollination and fertilization in most angiosperms is approximately: A) 1-2 hours B) 12-24 hours C) 24-48 hours D) 3-7 days

C) 24-48 hours. Explanation: This indicates the typical timeframe for pollen tube growth and fertilization.

The formation of fruit without the stimulation of pollination and fertilization, resulting in seedless fruits, is called what?

Parthenocarpy. Explanation: This process leads to the development of fruit without viable seeds.

Which two plant hormones are mentioned as being able to induce parthenocarpy in some fruits?

Gibberellins and auxins. Explanation: These hormones can mimic the stimulus normally provided by pollination and fertilization.

What term describes the process where pollination and fertilization occur, and the fruit forms, but the embryo aborts, resulting in no viable seed?

Stenospermocarpy. Explanation: This is another mechanism for producing seedless fruits, distinct from true parthenocarpy.

Botanically, the true fruit is defined as just the enlarged ovary. True or False?

True. Explanation: While accessory tissues can contribute to what we call "fruit," the true fruit develops specifically from the ovary.

Besides auxin, which other plant hormone is mentioned as stimulating fruit set in grapes?

Cytokinins. Explanation: Both auxin and cytokinins play roles in fruit development.

A chief problem in fruit production is obtaining the optimal level of fruit setting. What is the consequence of too heavy a fruit set?

Undesirable small, poor-quality fruits that mature late, possibly resulting in little or no crop the following year. Explanation: Excessive fruit load can deplete resources and reduce quality.

Removing the achenes (the small, seed-like parts) from the surface of a strawberry at an early growth stage causes the fruit to be lopsided. This indicates a relationship between fruit growth and the presence of which hormone?

Auxin. Explanation: Auxin produced by the achenes is necessary for the uniform development of the strawberry fruit.

Application of gibberellin to Thompson seedless grape clusters at an early berry development stage markedly increases what?

Ultimate fruit size. Explanation: Gibberellins can promote cell enlargement in fruits.

Fruits generally increase in size primarily due to cell enlargement after an initial period of intense cell division. True or False?

True. Explanation: Fruit growth typically involves an initial phase of cell division followed by a longer phase of cell expansion.

Which of the following fruits explicitly shows a double sigmoid growth curve? A) Orange B) Apple C) Cherry D) Grape

D) Grape. Explanation: Grapes and stone fruits like cherries exhibit this growth pattern with two periods of rapid growth.

Fruits that experience a burst of respiration and release high levels of ethylene as they ripen are called what?

Climacteric fruits. Explanation: This rise in respiration and ethylene production characterizes their ripening.

Which of the following is a climacteric fruit? A) Cucumber B) Apple C) Strawberry D) Lemon

B) Apple. Explanation: Apples are a classic example of a climacteric fruit, along with bananas and tomatoes.

Which type of tree is believed to be over 2,000 thousand (2 million) years old in the eastern Mediterranean area, as mentioned in the context of senescence?

Olive trees. Explanation: This highlights the exceptional longevity of some olive trees.

Senescence is defined as an irreversible deteriorative change in living organisms leading to cellular and tissue breakdown and death. True or False?

True. Explanation: Senescence is the process of aging and eventual death in plants.

Senescence can occur at the level of individual plants (whole plant senescence), and at what other levels?

Leaves, seeds, flowers, or fruits (organ senescence). Explanation: Senescence can affect the entire plant or specific organs.

How can vegetatively propagated clones theoretically extend the "life" of a plant indefinitely?

By continuously propagating new plants from existing ones. Explanation: Clones are genetically identical copies, allowing for indefinite continuation of the genetic line.

During leaf senescence, levels of DNA, RNA, proteins, chlorophyll, photosynthesis, starch, auxins, and gibberellins generally: A) Increase B) Remain stable C) Decrease D) Fluctuate unpredictably

C) Decrease. Explanation: These essential compounds are broken down and remobilized during senescence.

Plant senescence can be postponed in many plants by picking off the flowers before seeds start to form. True or False?

True. Explanation: This prevents the plant from entering the reproductive phase that often triggers senescence.

A natural substance produced by the plant itself that controls plant activities is termed a , while include these natural substances as well as synthetic chemicals not found in plants. A) Plant growth regulator, plant hormone B) Plant hormone, plant growth regulator C) Phytohormone, growth stimulant D) Chemical messenger, natural compound

B) Plant hormone, plant growth regulator. Explanation: Plant hormones are naturally occurring, while growth regulators encompass both natural and synthetic compounds.

Name the five traditionally recognized groups of natural plant hormones.

Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic Acid. Explanation: These are the primary classes of plant hormones.

Besides the five traditional groups, name at least two additional hormone classes recently identified.

Brassinolides, Salicylic acid, Jasmonates, Systemin. Explanation: These represent newer discoveries in plant hormone research.

Natural auxins primarily originate in which two locations within the plant?

Meristems and enlarging tissues. Explanation: Auxins are produced in actively growing regions.

The blockage of lateral bud growth by the presence of terminal buds is caused by auxins produced in the shoot tip. This phenomenon is called what?

Apical dominance. Explanation: Auxin produced by the apical bud inhibits the growth of lateral buds.

What is the most widespread auxin that occurs naturally in plants?

Indoleacetic acid (IAA). Explanation: IAA is a prominent natural auxin.

Which of the following is not listed as an important commercial use of synthetic auxins? A) Adventitious root initiation B) Weed control C) Promoting stem sprouting D) Tissue culture

C) Promoting stem sprouting. Explanation: Synthetic auxins are used for inhibiting stem sprouting, not promoting it.

Gibberellins were first discovered by Japanese researchers studying a disease of rice plants caused by what fungus?

Gibberella fujikuroi. Explanation: The fungus was found to produce substances that caused abnormal growth in rice.

Unlike auxin, which primarily moves apex-to-base, gibberellins can translocate easily in the plant in which directions?

Both directions. Explanation: Gibberellins have more bidirectional movement compared to auxins.

Application of gibberellin sprays is a common agricultural practice to increase the fruit size of what specific type of grapes?

Seedless grapes (e.g., Thompson Seedless). Explanation: Gibberellins are used to enlarge the berries of seedless grape varieties.

Treating certain dwarf cultivars of peas and corn with gibberellins can make them grow to a normal height, indicating that these dwarfed plants lack a normal level of gibberellin. True or False?

True. Explanation: This suggests that the dwarfism is often due to a deficiency in natural gibberellin production.

Cytokinins primarily promote cell , but also participate in other aspects of growth and development, such as tissue differentiation and retardation of leaf senescence. A) Elongation B) Division C) Dormancy D) Photosynthesis

B) Division. Explanation: Cytokinins are key regulators of cell division.

Which part of the plant is primarily responsible for supplying cytokinins upwards to the shoots?

Roots. Explanation: Roots are a significant site of cytokinin synthesis.

Ethylene is unique among plant hormones because of its physical state at room temperature. What is that state?

Gas. Explanation: Its gaseous nature allows it to diffuse and affect nearby plants.

What commercial application of ethylene involves treating oranges, lemons, and grapefruit to enhance their color?

Degreening. Explanation: Ethylene promotes the breakdown of chlorophyll, revealing underlying pigments.

Abscisic acid (ABA) has two major roles in a plant's life: regulation of processes in and acting as a mobile hormone that initiates plant responses to cold and water stress. A) Photosynthesis, growth B) Seed development, stress C) Vegetative growth, signaling D) Flowering, dormancy

B) Seed development, stress. Explanation: ABA is crucial for inducing seed dormancy and mediating responses to environmental stresses like drought and cold.