acid) and free fatty acids, but the roles of these compounds in defense remain
uncertain. Although plant hormones play important roles for many plant interactions, including pathogenic responses, only little plant hormone research has been
conducted on Cuscuta. Also, little is known about the influence of hormonal changes
to Cuscuta, such as effect to haustorium induction and reciprocal interaction with
host plant. Furuhashi et al. [84] firstly tested several host plant species for Cuscuta
parasitization and also observed Cuscuta plant interaction in the field, in order to find
interesting interactive relationship. They reported the new, unique phenomenon that
a parasitic plant induced hypertrophy together with vascular tissue differentiation in
the host plant stem. Plant hormone analysis clarified that cytokinin played a major
role in this process. Momordica charantia hypertrophy response might be derived
from resistance, while Cuscuta grow rapidly under the presence of hypertrophy
response.
4.2
Impact on Host Pigment Content
Obligate parasites are not able to develop without assimilate supplies from their
hosts because of their inability to perform any photosynthetic activity on their own or
such photosynthetic capacity is very low [6, 50]. Their dependence on the host plant
is therefore stronger, as well as their negative impact in terms of reducing chlorophyll and accessory pigments in the host plant [77]. Saric-Krsmanovic et al. [78, 79]
showed a significant reduction in chlorophyll a, chlorophyll b, and carotenoids in
infested alfalfa and sugar beet plants, compared to noninfested plants. Such reductions in chlorophyll a, chlorophyll b, and carotenoids were higher in infested alfalfa
than infested sugar beet plants. Similarly, Fathoulla and Duhoky [80] found that
different Cuscuta species caused not only morphological and anatomical changes in
their hosts but also reduced their chlorophyll contents. Specifically, C. campestris
and C. chinensis caused significant decrease in total chlorophyll contents in three
tested hosts Capsicum annuum, Coleus spp., and Helianthus annuus, while the
smallest reduction was caused by C. monogyna. Furthermore, these authors also
revealed a significant variation in the chlorophyll content in the leaves of the same
plant parasitized by different Cuscuta species. The differences in the infection
between the different hosts by the same Cuscuta sp. may be related to the differences
in nutrient status or sizes of the host (metabolic activities) [81].
4.3
Impact on Host Chlorophyll Fluorescence
Methods based on chlorophyll fluorescence have been used in many studies to
monitor the effects of various stress factors on plants, such as water deficit, nitrogen
deficit, extreme temperatures, and high salt concentrations, or to study changes in
photosynthetic processes caused by herbicides or pathogen infection [82–85]. SaricKrsmanovic et al. [78] have discovered possibilities that used chlorophyll fluorescence as an indicator of stress in host plants parasitized by field dodder. Most of the
110
M. Sarić-Krsmanović
uncertain. Although plant hormones play important roles for many plant interactions, including pathogenic responses, only little plant hormone research has been
conducted on Cuscuta. Also, little is known about the influence of hormonal changes
to Cuscuta, such as effect to haustorium induction and reciprocal interaction with
host plant. Furuhashi et al. [84] firstly tested several host plant species for Cuscuta
parasitization and also observed Cuscuta plant interaction in the field, in order to find
interesting interactive relationship. They reported the new, unique phenomenon that
a parasitic plant induced hypertrophy together with vascular tissue differentiation in
the host plant stem. Plant hormone analysis clarified that cytokinin played a major
role in this process. Momordica charantia hypertrophy response might be derived
from resistance, while Cuscuta grow rapidly under the presence of hypertrophy
response.
4.2
Impact on Host Pigment Content
Obligate parasites are not able to develop without assimilate supplies from their
hosts because of their inability to perform any photosynthetic activity on their own or
such photosynthetic capacity is very low [6, 50]. Their dependence on the host plant
is therefore stronger, as well as their negative impact in terms of reducing chlorophyll and accessory pigments in the host plant [77]. Saric-Krsmanovic et al. [78, 79]
showed a significant reduction in chlorophyll a, chlorophyll b, and carotenoids in
infested alfalfa and sugar beet plants, compared to noninfested plants. Such reductions in chlorophyll a, chlorophyll b, and carotenoids were higher in infested alfalfa
than infested sugar beet plants. Similarly, Fathoulla and Duhoky [80] found that
different Cuscuta species caused not only morphological and anatomical changes in
their hosts but also reduced their chlorophyll contents. Specifically, C. campestris
and C. chinensis caused significant decrease in total chlorophyll contents in three
tested hosts Capsicum annuum, Coleus spp., and Helianthus annuus, while the
smallest reduction was caused by C. monogyna. Furthermore, these authors also
revealed a significant variation in the chlorophyll content in the leaves of the same
plant parasitized by different Cuscuta species. The differences in the infection
between the different hosts by the same Cuscuta sp. may be related to the differences
in nutrient status or sizes of the host (metabolic activities) [81].
4.3
Impact on Host Chlorophyll Fluorescence
Methods based on chlorophyll fluorescence have been used in many studies to
monitor the effects of various stress factors on plants, such as water deficit, nitrogen
deficit, extreme temperatures, and high salt concentrations, or to study changes in
photosynthetic processes caused by herbicides or pathogen infection [82–85]. SaricKrsmanovic et al. [78] have discovered possibilities that used chlorophyll fluorescence as an indicator of stress in host plants parasitized by field dodder. Most of the
110
M. Sarić-Krsmanović