Crop Science Review Manual

Comprehensive review flashcards covering agricultural concepts, plant classification, anatomy, physiology, crop production, soil management, plant breeding, and farm entrepreneurship based on the Crop Science lecture manual.

What Philippine legislation enacted in 1997 mandated the modernization of the country's agricultural sector?

The Agriculture and Fisheries Modernization Act (AFMA), also designated as Republic Act 8435.

According to world land utilization data, what percentages of the total 150 million $km^2$ land area are occupied by arable land, permanent crops, and pastures?

Arable land comprises $10\%$, permanent crops account for $1\%$, and meadows and pastures cover $24\%$ of the total land area.

What are the two major divisions of crop science, and what specialized fields are encompassed within horticulture?

The two main divisions are Agronomy and Horticulture. Horticulture includes olericulture (vegetables), pomology (fruits), floriculture (flowers), nursery management, and landscape gardening.

What complete floral anatomy and major reproductive parts are illustrated in this diagram?

A complete flower displaying the male stamen (anther and filament), the female pistil (stigma, style, and ovary), the petals (corolla), and the sepals (calyx).

What distinct internal structures differentiate the dicotyledon and monocotyledon seeds shown in this diagram?

The dicotyledon seed contains two cotyledons flanking the epicotyl, hypocotyl, and seed coat; the monocotyledon seed contains a large endosperm, a single cotyledon, epicotyl, radicle, and surrounding seed coat.

What major structural organelles are present in plant cells but absent in animal cells?

Plant cells contain a cellulose cell wall, chloroplasts, and a large central vacuole, all of which are absent in animal cells (which conversely possess centrioles and lysosomes).

What are the three distinct layers of a plant cell wall and their primary roles?

1. Middle lamella: contains pectin that cements adjacent cell walls together; 2. Primary wall: thin and stretchable layer formed during cell growth composed of cellulose microfibrils and plasmodesmata; 3. Secondary wall: rigid, thickened structural layer formed after cell growth ceases.

What are the three classes of non-pigmented leucoplasts and the specific storage materials they synthesize?

Amyloplasts synthesize and store starch, proteinplasts store proteins, and elaioplasts synthesize and store fats and oils.

What are the three primary types of plant meristematic tissues and where are they located?

Apical meristems are at the growing tips of roots and shoots; lateral meristems (vascular cambium and cork cambium/phellogen) run parallel to the sides of stems and roots; intercalary meristems are located at internodes and bases of young leaves.

What are the primary specialized cell types that comprise plant sclerenchyma tissue?

Fibers (long bast fibers with thick walls), sclereids or stone cells (lignified protective cells), and cork (cells impregnated with waxy suberin).

What are the chief conducting elements and associated cells found within xylem and phloem?

Xylem contains vessel elements and xylem parenchyma cells; phloem contains sieve-tube elements, companion cells, phloem parenchyma, and phloem fibers.

How do rhizomes, runners (stolons), and corms differ anatomically as specialized stems?

A rhizome is a horizontal subterranean stem; a runner or stolon is an indeterminate above-ground horizontal stem developing plantlets at nodes; a corm is an enlarged, solid, fleshy underground stem base covered with scale leaves.

What physiological criteria distinguish orthodox seeds from recalcitrant seeds?

Orthodox seeds dry naturally on the mother plant to $\le 20\%$ moisture content and can survive drying below $5\%$ moisture content for cold storage; recalcitrant seeds are shed at $50\text{--}70\%$ moisture content, lose viability if dried below $12\text{--}30\%$, and cannot tolerate freezing or chilling temperatures.

What is the structural difference between an aggregate fruit and a multiple (composite) fruit?

An aggregate fruit develops from multiple separate ovaries of a single flower with an apocarpous pistil (e.g., strawberry); a multiple fruit develops from the consolidated ovaries of many individual flowers in an inflorescence (e.g., pineapple).

How is stimulative parthenocarpy distinguished from vegetative parthenocarpy?

Stimulative parthenocarpy requires pollination or an external stimulus to set seedless fruit (e.g., banana, watermelon); vegetative parthenocarpy produces seedless fruit completely without pollination or external stimulation (e.g., cucumber, citrus, pineapple).

What is the central chemical structure of a chlorophyll molecule, and which metal ion occupies its center?

Chlorophyll consists of a porphyrin ring composed of four pyrrole rings joined by carbon linkages, with a single magnesium atom ($Mg$) bound in the center.

What three photosynthetic carbon fixation systems and leaf anatomical designs are compared across these cross-sections?

$C_3$ leaf anatomy (standard mesophyll arrangement lacking Kranz anatomy), $C_4$ leaf anatomy (Kranz-type anatomy featuring prominent bundle sheath cells), and the CAM pathway (temporal separation of nocturnal malic acid accumulation and daytime Calvin cycle).

What are the initial carbon dioxide acceptors and first stable products in $C_3$, $C_4$, and CAM pathways?

In $C_3$, ribulose-1,5-bisphosphate (RuBP) fixes $CO_2$ into 3-phosphoglycerate (3-PGA); in $C_4$, phosphoenolpyruvate (PEP) fixes $CO_2$ into oxaloacetate (OAA); in CAM, PEP fixes $CO_2$ into OAA at night, while RuBP fixes liberated $CO_2$ into 3-PGA during the day.

Where do the three major stages of plant cellular respiration occur and what are their respective ATP generation mechanisms?

Glycolysis occurs in the cytosol (producing 2 net ATP via substrate-level phosphorylation); the Krebs Cycle occurs in the mitochondrial matrix (yielding 2 ATP via substrate-level phosphorylation, plus NADH and $FADH_2$); the Electron Transport System occurs in the inner mitochondrial membrane (yielding ATP via oxidative phosphorylation).

What three types of transpiration are categorized by the exit point on the plant illustrated here?

Lenticular transpiration (through lenticels on woody bark), cuticular transpiration (across the waxy leaf cuticle), and stomatal transpiration (through open stomata in the epidermis).

How much latent heat of vaporization is required to evaporate one gram of water during plant transpiration?

$539\,cal/g$ of water evaporated.

What are the apoplastic, symplastic, and transmembrane routes of water movement through root cortex tissues?

The apoplastic pathway travels through extracellular capillary cell wall spaces and intercellular voids; the symplastic pathway moves through the cytoplasm between cells via plasmodesmata; the transmembrane route crosses through plasma membranes and vacuoles (tonoplast).

Why do deficiency symptoms of mobile nutrients appear on older leaves, whereas immobile nutrient deficiencies appear on young leaves?

Mobile nutrients ($N$, $P$, $K$, $Mg$) are remobilized and exported from mature tissues to younger growing tissues, causing chlorosis in older leaves; immobile nutrients ($Ca$, $Fe$, $B$) cannot be translocated once assimilated, causing symptoms to develop in new growth.

What differentiates plant tropisms from nastic movements?

Tropisms are directional growth responses governed by the orientation of an environmental stimulus (e.g., phototropism, gravitropism); nastic movements are non-directional responses triggered by internal timing or non-directional stimuli (e.g., nyctinasty, seismonasty).

What is the amino acid precursor of indole-3-acetic acid (IAA), and what characterizes its movement through tissues?

IAA is synthesized from tryptophan and exhibits polar transport, moving basipetally in shoots and acropetally toward root tips through parenchyma and vascular cells.

What unique physical state distinguishes ethylene from other plant hormones, and what is its biochemical precursor?

Ethylene is the only phytohormone existing as a gas; it is synthesized from the amino acid precursor methionine.

How does Mitscherlich's Law of Diminishing Return differ conceptually from Blackman's Theory of Limiting Factors?

Blackman's theory assumes a linear response where a process is limited strictly by the slowest factor, whereas Mitscherlich's law demonstrates that yield increments follow a curvilinear response proportional to the decrement from maximum yield as the limiting factor is added.

What specific mode of seed germination is demonstrated in this developmental sequence of a bean seedling?

Epigeous (epigeal) germination, wherein the hypocotyl elongates, arching upward to elevate the cotyledons above the soil surface.

How do scarification, stratification, and vernalization differ in breaking dormancy or inducing developmental changes?

Scarification physically, chemically, or mechanically alters the impermeable seed coat; stratification chills or warms imbibed seeds in moist media to break embryo dormancy; vernalization chills hydrated seeds or plants specifically to induce floral initiation.

What is the genetic and reproductive distinction between obligate and facultative apomixis?

Obligate apomicts reproduce strictly through asexual seed formation without fertilization (e.g., mangosteen, lanzones); facultative apomicts can reproduce either sexually or through apomixis (e.g., mango, citrus).

What are the roles of the scion, rootstock, and interstock in vegetative grafting?

The scion provides the dormant upper shoots that form the desired fruiting canopy; the rootstock establishes the root system and anchors the plant; the interstock is inserted between scion and rootstock to overcome graft incompatibility or control vigor.

What define the three cardinal temperatures governing enzyme activities in crops?

The minimum temperature (below which reaction velocity reaches zero due to enzyme inactivation), the optimum temperature (where reaction velocity is maximized), and the maximum temperature (above which denaturation halts enzymatic activity).

What is the formula for calculating soil bulk density ($B.D.$), and what threshold indicates structural compaction?

$B.D. = \frac{W_s}{V_t}$, where $W_s$ is the oven-dry soil weight in grams and $V_t$ is the total core volume in $cm^3$; bulk density values exceeding $1.3\,g/cm^3$ denote compacted soils.

What chemical and nutrient availability hazards arise when soil pH falls below $5.0$ or rises above $8.0$?

Below $pH\,5.0$, $Ca$, $Mg$, $K$, and $P$ become deficient while $Al$, $Fe$, and $Mn$ reach toxic solubility; above $pH\,8.0$, micronutrients (except $Mo$) become unavailable, $Fe$ deficiency occurs, and phosphorus precipitates as insoluble calcium phosphates.

What are the three population-level modes of selection and their respective impacts on phenotypic variance?

Stabilizing selection favors intermediate phenotypes and narrows variance; directional selection favors an extreme phenotype and shifts the population mean; disruptive selection favors both extreme phenotypes and splits the population into distinct classes.

What standard tag colors designate the Breeder, Foundation, Registered, and Certified seed classes in the Philippines?

Breeder seed is tagged white, Foundation seed is tagged red, Registered seed is tagged green, and Certified seed is tagged blue.

What distinguishes zero tillage, mulch tillage, and strip tillage within conservation agriculture?

Zero tillage plants seeds directly into undisturbed soil without prior cultivation; mulch tillage leaves crop residues across the entire surface as protective mulch; strip tillage tills narrow seeding strips while leaving inter-row strips uncultivated and residue-covered.

How do the wetbed, dapog, and dry-bed methods of raising rice seedlings differ in nursery duration before transplanting?

Wetbed seedlings are ready in $25\text{--}30\text{ days}$; dapog seedlings (raised on banana/plastic sheets) are ready in $10\text{--}14\text{ days}$; dry-bed seedlings in rainfed areas require $20\text{--}40\text{ days}$.

What is the physiological difference between climacteric and non-climacteric fruit postharvest behavior?

Climacteric fruits (e.g., mango, banana, tomato) display a pronounced respiratory and ethylene burst at maturity and can ripen after harvest; non-climacteric fruits (e.g., citrus, pineapple, watermelon) exhibit steadily declining respiration and must reach full ripeness on the plant.

What are the postharvest operations known as curing, dehaulming, and tuxying?

Curing is the self-healing and suberization of wounded tissues on root, tuber, or bulb crops; dehaulming is cutting potato vines one week before harvest to set skins; tuxying is separating the outer fiber bands from leaf sheaths in abaca.

How do parallel cropping, companion cropping, and synergetic cropping operate in multiple cropping patterns?

Parallel cropping combines crops of differing niches with zero competition (e.g., mungbean + maize); companion cropping produces yields identical to sole crops without competition (e.g., mustard + sugarcane); synergetic cropping produces yields for both crops that exceed their sole-crop yields per unit area (e.g., sugarcane + potato).

What are the farm business equations for Breakeven Yield ($BEY$), Cost per kilogram ($\text{Cost/kg}$), and Return on Investment ($ROI$)?

$BEY = \frac{\text{Total cost}}{\text{Unit price}}$; $\text{Cost/kg} = \frac{\text{Total cost/ha}}{\text{Yield in kg/ha}}$; $ROI = \frac{\text{Total income or gross return}}{\text{Total cost excluding interest expense}}$.