17. FISIOLOGIA VEGETAL - LUIS ROSSI 17
CLOROPLASTOS:
MEMBRANA DEL TILACOIDE
COMPOSICION QUIMICA :
• -CLOROFILAS:10%.
Son complejos de
porfirinas-Mg.
• Tipos: a,b,c y d.
• Formadas por un
núcleo porfirínico
tetrapirrólico con un
átomo de Mg en el
centro; presentan una
cadena hidrocarbonada
de fitol embebida en la
membrana del
tilacoide.
Mg
18. FISIOLOGIA VEGETAL - LUIS ROSSI 18
CLOROPLASTOS:
MEMBRANA DEL TILACOIDE
COMPOSICION QUIMICA :
• - CAROTENOIDES: 2%.
• Pueden ser de color amarillo o
anaranjado.
• Tipos: Los carotenos y las xantófilas.
• El más abundante es el ß-caroteno
• Función:
• colector de la energía luminosa, y
• protegen a la clorofila contra la
fotooxidación por el O2.
19.
20.
21.
22. FISIOLOGIA VEGETAL - LUIS ROSSI 22
FASES DE LA FOTOSINTESIS
• Comprende 2
fases:
• La fase
luminosa que
se lleva a
cabo a nivel
de las
membranas
de los
tilacoides y
• La fase
oscura que
se lleva a
cabo a nivel
del estroma.
23.
24. FISIOLOGIA VEGETAL - LUIS ROSSI 24
PS II
PS I
H2O
2e-
2e-
2e-
1/2 O2
2H+
NADP+
NADPH
+ H+
PQ
ferredoxina
2e-
2e-
2hv
2hv
ADP + Pi
ATP
Cit
b - f
PC
FOTOFOSFORILACION NO CICLICA
FOTOFOSRORILACION CICLICA
FASE LUMINOSA- ESQUEMA Z
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35. FISIOLOGIA VEGETAL - LUIS ROSSI 35
PLANTAS C4
CELULAS DEL MESOFILO CELULAS DE VAINA
VASCULAR
CO2
C1 + C3 C4
C4 C3+C1
C3 +Productos
CICLO
DE
CALVIN
AMP + Ppi ATP
H
A
Z
V
A
S
C
U
L
A
R
36.
37.
38.
39. FISIOLOGIA VEGETAL - LUIS ROSSI 39
FOTORESPIRACION
• Proceso que se da en las plantas debido a la
característica de la RUBISCO de funcionar en una
forma diferente a como lo hace durante la
Fotosíntesis de acuerdo a la [ ] de CO2 que se
presenta en el medio, lo que provoca una pérdida
del carbono en la forma de CO2, durante los
períodos de luz.
40.
41.
42. 1. Fotosintesis neta = Fotosíntesis bruta – Respiración
(AHORRO) = INGRESO - GASTO
2. Fotosíntesis neta = Fotosíntesis bruta - (Respiración + Fotorespiración)
¿Que tipo de planta responde mucho mejor al
a) Aumento en la concentración de CO2 atmosférico
b) Abonamiento orgánico
Las plantas C4 ¿ Fotorespiran?
Igualdad Tipo de planta ¿ C3
o C4 ?
1 ¿?
2 ¿?
43. Figura 1. Destinos posibles de la Chl excitada. Cuando la Chl absorbe luz se excita desde su estado
de reposo a su estado singlete excitado, 1Chl*. De allí tiene varios modos de regresar de nuevo al
estado de reposo. Puede regresar emitiendo luz que se observa como fluorescencia (1). La energía de
excitación puede usarse como combustible para las reacciones fotosintéticas(2),o puede desexcitarse
disipando calor. Estos dos últimos mecanismos reducen la cantidad de fluorescencia de la clorofila.
Por eso se hace referencia a ellos como qP y DNF de la fluorescencia de la clorofila. Finalmente, vía
cruzamiento intersistemas1Chl*, produce3Chl* (4), que a su vez es capaz de producir 1O2*, una
especie de oxígeno muy reactivo.
44.
45. Los estados de activación de oxígeno.
La primera reacción de
reducción es superóxido
Las reducciones subsiguientes
forman peróxido de hidrógeno,
radical hidroxilo y agua.
46. ¿QUÉ ES UN RADICAL LIBRE?
Radical libre es aquella especie química capaz de existir
independientemente y que posee uno o más electrones
desapareados.
Este electrón desapareado confiere al radical libre cierto grado de
inestabilidad. para alcanzar la estabilidad, el radical libre puede
perder este electrón, en cuyo caso se comporta como agente oxidante.
Activación del oxígeno
Puede ocurrir por dos mecanismos diferentes
La absorción de energía suficiente para invertir el giro de uno de los electrones
desapareados
La forma birradical de oxígeno está en un estado fundamental triplete
debido a que los electrones tienen espines paralelos
Si el oxígeno triplete absorbe la energía suficiente para invertir el giro de uno de sus
electrones desapareados, se forma el estado de singlete, tienen espines opuestos
47.
48. SITIOS DE PRODUCCIÓN DE OXÍGENO ACTIVO
CLOROPLASTOS
MITOCONDRIAS
RETICULO ENDOPLASMICO
Microcuerpos Las membranas plasmáticas
PARED CELULAR
49. Oxígeno activado y agentes que generan radicales libres de oxígeno, tales como las
radiaciones ionizantes, inducir lesiones en el ADN que numerosas deleciones,
mutaciones causan y otros efectos genéticos letales.
El daño oxidativo al ADN
50.
51. Overall picture of the regulation of
photon capture and the protection and
repair of photodamage.
Protection against photodamage is a
multilevel process.
The first line of defense is suppression
of damage by
quenching of excess excitation as heat.
If this defense is not
sufficient and toxic photoproducts
form, a variety of scavenging
systems eliminate the reactive
photoproducts. If this second line of
defense also fails, the photoproducts
can damage the D1 protein of
photosystem II. This damage leads to
photoinhibition. The D1 protein is then
excised
from the PSII reaction center and
degraded. A newly synthesized
D1 is reinserted into the PSII reaction
center to form a functional unit. (After
Asada 1999.)
52. MECANISMOS DE DEFENSA
No enzimáticas:
Ácido ascórbico
Glutatión
Tocoferol (Vitamina E)
Carotenoides
Enzimáticas:
Superóxido dismutasa
Catalasa
Ascorbato peroxidasa
MANTIENEN EL (ROS) EN NIVELES NO PERJUDICIALES
53.
54. ANTIOXIDANTES
Es una sustancia capaz de neutralizar la acción de un radical libre. Muchos alimentos
vegetales los contienen en gran cantidad. Son las mismas sustancias que les protegen de
ser fácilmente oxidados por la acción del aire y el sol.
66. MICRONUTRIENTE FUNCION
Boron A primary function of boron is related to cell wall formation, so boron-
deficient plants may be stunted. Sugar transport in plants, flower
retention and pollen formation and germination also are affected by
boron. Seed and grain production are reduced with low boron supply.
Boron-deficiency symptoms first appear at the growing points. This
results in a stunted appearance (rosetting), barren ears due to poor
pollination, hollow stems and fruit (hollow heart) and brittle, discolored
leaves and loss of fruiting bodies.
Boron deficiencies are found mainly in acid, sandy soils in regions of
high rainfall, and those with low soil organic matter. Borate ions are
mobile in soil and can be leached from the root zone. Boron
deficiencies are more pronounced during drought periods when root
activity is restricted.
67. Copper Copper is necessary for carbohydrate and nitrogen metabolism and,
inadequate copper results in stunting of plants. Copper also is required for
lignin synthesis which is needed for cell wall strength and prevention of
wilting. Deficiency symptoms of copper are dieback of stems and twigs,
yellowing of leaves, stunted growth and pale green leaves that wither
easily.
Copper deficiencies are mainly reported on sandy soils which are low in
organic matter. Copper uptake decreases as soil pH increases. Increased
phosphorus and iron availability in soils decreases copper uptake by
plants.
68. Iron Iron is involved in the production of chlorophyll, and iron chlorosis is
easily recognized on iron-sensitive crops growing on calcareous soils.
Iron also is a component of many enzymes associated with energy
transfer, nitrogen reduction and fixation, and lignin formation. Iron is
associated with sulfur in plants to form compounds that catalyze other
reactions. Iron deficiencies are mainly manifested by yellow leaves due
to low levels of chlorophyll. Leaf yellowing first appears on the younger
upper leaves in interveinal tissues. Severe iron deficiencies cause
leaves to turn completely yellow or almost white, and then brown as
leaves die.
Iron deficiencies are found mainly on high pH soils, although some acid,
sandy soils low in organic matter also may be iron-deficient. Cool, wet
weather enhances iron deficiencies, especially on soils with marginal
levels of available iron. Poorly aerated or compacted soils also reduce
iron uptake by plants. Uptake of iron decreases with increased soil pH,
and is adversely affected by high levels of available phosphorus,
manganese and zinc in soils.
69. Manganese Manganese is necessary in photosynthesis, nitrogen metabolism and to
form other compounds required for plant metabolism. Interveinal chlorosis
is a characteristic manganese-deficiency symptom. In very severe
manganese cases, brown necrotic spots appear on leaves, resulting in
premature leaf drop. Delayed maturity is another deficiency symptom in
some species. White/gray spots on leaves of some cereal crops is a sign
of manganese deficienc.
Manganese deficiencies mainly occur on organic soils, high-pH soils,
sandy soils low in organic matter, and on over-limed soils. Soil
manganese may be less available in dry, well-aerated soils, but can
become more available under wet soil conditions when manganese is
reduced to the plant-available form. Conversely, manganese toxicity can
result in some acidic, high-manganese soils. Uptake of manganese
decreases with increased soil pH and is adversely affected by high levels
of available iron in soils.
70. Molybdenu
m
Molybdenum is involved in enzyme systems relating to nitrogen fixation
by bacteria growing symbiotically with legumes. Nitrogen metabolism,
protein synthesis and sulfur metabolism are also affected by
molybdenum. Molybdenum has a significant effect on pollen formation,
so fruit and grain formation are affected in molybdenum-deficient plants.
Because molybdenum requirements are so low, most plant species do
not exhibit molybdenum-deficiency symptoms. These deficiency
symptoms in legumes are mainly exhibited as nitrogen-deficiency
symptoms because of the primary role of molybdenum in nitrogen
fixation. Unlike the other micronutrients, molybdenum-deficiency
symptoms are not confined mainly to the youngest leaves because
molybdenum is mobile in plants. The characteristic molybdenum
deficiency symptom in some vegetable crops is irregular leaf blade
formation known as whiptail, but interveinal mottling and marginal
chlorosis of older leaves also have been observed.
Molybdenum deficiencies are found mainly on acid, sandy soils in humid
regions. Molybdenum uptake by plants increases with increased soil pH,
which is opposite that of the other micronutrients. Molybdenum
deficiencies in legumes may be corrected by liming acid soils rather than
by molybdenum applications. However, seed treatment with
molybdenum sources may be more economical than liming in some
areas.
71. Zinc Zinc is an essential component of various enzyme systems for energy
production, protein synthesis, and growth regulation. Zinc deficient plants
also exhibit delayed maturity. Zinc is not mobile in plants so zinc-
deficiency symptoms occur mainly in new growth. Poor mobility in plants
suggests the need for a constant supply of available zinc for optimum
growth. The most visible zinc deficiency symptoms are short internodes
and a decrease in leaf size. Delayed maturity also is a symptom of zinc-
deficient plants.
Zinc deficiencies are mainly found on sandy soils low in organic matter
and on organic soils. Zinc deficiencies occur more often during cold, wet
spring weather and are related to reduced root growth and activity as well
as lower microbial activity decreases zinc release from soil organic matter.
Zinc uptake by plants decreases with increased soil pH. Uptake of zinc
also is adversely affected by high levels of available phosphorus and iron
in soils.
72. Chloride Because chloride is a mobile anion in plants, most of its functions relate to
salt effects (stomatal opening) and electrical charge balance in
physiological functions in plants. Chloride also indirectly affects plant
growth by stomatal regulation of water loss. Wilting and restricted, highly
branched root systems are the main chloride-deficiency symptoms, which
are found mainly in cereal crops.
Most soils contain sufficient levels of chloride for adequate plant nutrition.
However, reported chloride deficiencies have been reported on sandy
soils in high rainfall areas or those derived from low-chloride parent
materials. There are few areas of chloride-deficient so this micronutrient
generally is not considered in fertilizer programs. In addition, chloride is
applied to soils with KCl, the dominant potassium fertilizer. The role of
chloride in decreasing the incidence of various diseases in small grains is
perhaps more important than its nutritional role from a practical viewpoint.
73.
74.
75.
76. CLAVE PARA EL DIAGNOSTICO VISUAL DE DESÓRDENES DE
NUTRIENTES.
La “Clave para el diagnostico visual de desórdenes nutricionales” que se
muestra a continuación es una herramienta útil que puede ayudar a
diagnosticar problemas nutricionales específicos en cultivos.
La clave le pregunta primero escoger si los síntomas visuales observados
estaban en las hojas superiores o en las inferiores.
Debajo de estas dos primeras selecciones se encuentran cuatro recuadros
con descripciones de diferentes síntomas visuales que pueden aparecer en
plantas de apariencia no saludable.
Si encuentra un recuadro que concuerda con el problema que observa en sus
plantas, mire al recuadro debajo de el para identificar el nutriente o grupo de
nutrientes que pueden causar esos síntomas cuando ellas son deficientes.
La fila inferior de recuadros, que no están presentes para tres de los
síntomas visuales, enumera los nutrientes que pueden causar síntomas
similares cuando ellos están presentes en cantidades excesivas o tóxicas.
77.
78.
79. Precautions in identifying nutrient stress symptoms include the following:
1. Many symptoms appear similar. For instance, N and S deficiency symptoms
can be very alike, depending upon plant growth stage and severity of deficiencies.
2. Multiple deficiencies and/or toxicities can occur at the same time. More than
one deficiency or toxicity can produce symptoms, or possibly an abundance of
one nutrient can induce the deficiency of another (e.g. excessive P causing Zn
deficiency).
3. Crop species, and even some cultivars of the same species, differ in their
ability to adapt to nutrient deficiencies and toxicities. For example, corn
is typically more sensitive to a Zn deficiency than barley and will show Zn
deficiency more clearly
80. 4. Pseudo (false) deficiency symptoms (visual symptoms appearing similar to nutrient
deficiency symptoms). Potential factors causing pseudo deficiency include, but are not
limited to, disease, drought, excess water, genetic abnormalities, herbicide and
pesticide residues, insects, and soil compaction.
5. Hidden hunger. Plants may be nutrient deficient without showing visual clues.
6. Field symptoms appear different than ‘ideal’ symptoms. Many of the plants
shown in this module as photographs were grown under controlled nutrient
conditions, and deficiency/toxicity symptoms observed in the field may or may not
appear as they do here.
Experience and knowledge of field history are excellent aids in determining
causes for nutrient stress.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
123. Chlorophyll meters are faster than tissue testing for N.
Samples can be taken often and repeated if results are questionable.
The meters are used to measure leaf greenness, which is positively related to leaf
chlorophyll content.
Research indicates a close correlation between leaf chlorophyll content and leaf N
content because much of the leaf N is contained in the chlorophyll.
124.
125. La absorción de nutrientes durante las primeras Nueve semanas de establecida la
plantación es muy baja, luego se incrementa , encontrándose que los valores máximos de
absorción ocurren en las semanas 18, 23 y 28, etapas que coinciden con las etapas de
mayor producción de frutos.
El período de mayor absorción se encuentra entre las semanas 9 y 26 y las épocas de
aplicación de fertilizantes que venían siendo utilizadas en Costa Rica no reflejaban los picos
altos de requerimientos de nutrientes.
Basándose en los datos obtenidos en el estudio de absorción de nutrientes a través del
tiempo se determinó que, en términos prácticos, la fertilización de la fresa puede
distribuirse en 3 etapas importantes del cultivo.
Durante las primeras 12 semanas se debe agregar el 20% del fertilizante requerido, en el
período comprendido entre las semanas 12 y 18 se debe aplicar 40% y entre las se-manas
20 y 24 se debe aplicar el
restante 40%.
126.
127.
128.
129. La existencia de plantas en las que hasta e l de la 50% del peso seco de la savia del xilema
es mineral, es el origen de los metodos modemos de "fitoextraccion".
Estos c onsisten en la reclamacion de suelos contaminados mediante el cultivo de estas
especies "hiperacumuladoras« y el procesamiento posterior del material vegetal
cosechado.
Estas especies capaces de extraer cantidades importantes de Se (alfalfa), Mn (Macadamia
neurophylla), Al (Te), Cu (Ipomoeaa alpina) y Ni (Psychotria caerorulescens)
entre otras, han sido identificadas.
