PHYLLOSPHERE
Definition:
(1).Plants’ above-ground elements, such as their leaves, stems, and flowers, create an ecological niche known
as the phyllosphere. The term phyllosphere is referred to as “the aerial part of the plant or the parts of a plant
above the ground usually surface of leaves, considered as a habitat for microorganisms.”
(2). Microorganisms establish compositionally complex communities on the leaf surface. The microbiome of
phyllosphere is rich in diversity of bacteria, fungi, actinomycetes, cyanobacteria, and viruses. The diversity,
dispersal, and community development on the leaf surface are based on the physiochemistry, environment,
and also the immunity of the host plant.
(3). A colonization process is an important event where both the microbe and the host plant have been
benefited. Microbes commonly established either epiphytic or endophytic mode of life cycle on phyllosphere
environment, which helps the host plant and functional communication with the surrounding environment.
(4). The phyllosphere is a ambient region for microbes to colonize. Microbial communities in the phyllosphere
are highly complex and consist of many cultured and uncultured microorganism. It has a heterogeneous
group of the microbial association at the micrometer scale area due to its diverse microenvironments
(habitats).
(5). The phyllospheric microbes are adapted to the insensitive environmental conditions, specifically microbial
epiphytes are highly exposed to atmospheric temperature, light, UV radiation, less water, and nutrient
availability. These external factors affect the composition and diversity of phyllospheric microbial
communities.
Leaf structure :
(1). The leaf is a highly organized and multi - layered plant organ which consists of the epidermis (upper and
lower) covered by a waxy cuticle that provides a physical barrier against abiotic and biotic stresses. The
epidermis involves many regulatory processes of leaf physiology including gas exchange, temperature
regulation, primary production, secretion of secondary metabolites, and water mobilization.
(2). A specialized epidermal cell such as stomata, hydathodes (modified stomata), and trichomes (outgrowth)
are there in the epidermis. The stomata are surrounded by two cupped hand cells called guard cells, which
may open or close due to internal water pressure.
(3). Inside the leaf, a layer of cells called the mesophyll, is present, usually two layers, namely, palisade layer
and the spongy layer. They contain chlorophyll and photosynthesis occurs in these cells.The palisade cells are
more column cells and the spongy cells are more loosely packed between the palisade layer and the lower
epidermis, and it allows for gas exchange.
(4). The veins of the leaf contain the vascular tissue, xylem and phloem are found in it. Veins run from tips of
the roots and are extended up to the edges of the leaves.
(5). The outer layer cells are called bundle sheath cells which circle the xylem and the phloem. The xylem
transports water and phloem transports sugar (food).Glandular trichome of the epidermis releases a wide
spectrum of leaf exudates, such as polysaccharide salts, lipids, volatile compounds, and proteins, and its
function is associated with plant–microbe and plant–insect interactions. But, non-glandular trichome involves
regulation of water tension, light absorption, and protect the leaf from UV radiation and heat as well as
drought tolerance .
, Phyllosphere habitat :
(1). The phyllosphere is a unique and dynamic habitat which constitutes irregular, and sometimes relatively
large microbial community inhabitant in the ecosystem . The total terrestrial phyllosphere area estimated is
around 6.4 × 108 (10 power 8) km2 (kilometre square).
(2). Variety of bacteria, filamentous fungi, and yeasts are naturally colonized on the phyllosphere region and
less frequently, protozoa and nematodes. These microorganisms exhibit commensalism and/or mutualism
(symbionts) or antagonism type of relationship on their host plants.
(3). The microbial association in phyllosphere has several advantages and importance to global processes
including biogeochemical cycles (carbon and nitrogen) and environmental impact.
Microbial diversity in the phyllosphere:
(1). The phyllosphere consists of diverse numerous microbial communities including bacteria, filamentous
fungi, yeasts, algae, and protozoans. Among the diverse community of microbes, bacteria are the predominant
community on leaves and its range is between 102 and 1012 g−1 of the leaf (Inacio et al. 2002).
(2).The conventional culture-based method has been used for the identification of different microbial
communities of the leaves. The cultivable yeasts genera such as Cryptococcus, Sporobolomyces, and
Rhodotorula and its species have been largely inhabitant in the plant leaf .
(3). Moreover, the culture-dependent methods have been used to study the abundance of filamentous fungi,
ranging from 102(read as ten power two) to 108 (read as ten power eigt) CFU g−1. Genera such as
Cladosporium, Alternaria, Penicillium, Acremonium, Mucor, and Aspergillus are the frequent filamentous
fungi colonizing as epiphytes and endophytes . However, the culture-independent strategy is the best to
investigate the diversity and distribution of specific bacterial groups of interests.
(4). Soils, water, air, tree buds, and plant debris from the previous crops are the sources for microbes in
phyllosphere. Those microorganisms may be habited in phyllosphere either transient or residual epiphytes.
(5). The atmospheric microflora, rainfall, humidity, wind, etc. can directly influence the transients of
microorganisms to the phyllosphere . During the plant growth period, the epiphytic bacterial population will
increase in quantity.
Bacterial diversity in the phyllosphere:
(1). Phyllosphere is a heterogeneous environment , bacteria are considered the most abundant inhabitants of
the leaves, and its average number is being around 106–108 cells (10 power 8 and 10 power 6).But the
population of epiphytic bacteria differs depending on the plant species and its surrounding environment. The
variation is mainly due to the physical and nutritional conditions of the phyllosphere. Commonly, the broad-
leaf plants have the highest number of bacteria than the grasses or waxy broad-leaf plants.
(2). Generally, the phyllosphere contains four major phyla of bacteria such as the Proteobacteria, Firmicutes,
Bacteroides, and Actinobacteria . Methylotrophic bacteria are predominant in phyllosphere which includes
genera such as Methylobacterium, Methylophilus, Methylibium, Hyphomicrobium, Methylocella,
Methylocapsa, and Methylocystis.
(3). Extensive research has been conducted on bacterial colonization in Arabidopsis thaliana and maize, with
Proteobacteria, Actinobacteria, and Bacteroidetes being the most abundant phyla colonizing the leaf and root
of A. thaliana.Studies have identified prevalent bacterial genera in A. thaliana, including Massilia,
Flavobacterium, Pseudomonas, and Rathayibacter, Deinococcus thermus on tree phyllosphere, and Bacillus
and Pantoea dominating lettuce. Also,Pseudomonas as the most abundant genus of phyllosphere region.
(4).The most notable bacterial pathogen is Pseudomonas syringae, it causes diseases in a wide range of
economically important plant species.
(5). Diazotrophic bacteria can use atmospheric dinitrogen (N2) as nitrogen source for its metabolic
activities.Bacterial diazotrophic include Beijerinckia, Azotobacter, Klebsiella, and Cyanobacteria (e.g., Nostoc,
Scytonema, and Stigonema).Diazotrophic nitrogen fixation has been reported in many species which contains
an enzyme nitrogenase.
Fungal diversity in phyllosphere:
(1). Fungi are saprophytic and they maybe associated with plants either epiphytic or endophytic, and mostly
they are known for their pathogenesis on plant system . Both epiphytic and endophytic fungi inhabiting the
leaf are of high species diversity with diverse metabolic functions ,such as leaf litter decomposition and
recycling the carbon and nitrogen.
Definition:
(1).Plants’ above-ground elements, such as their leaves, stems, and flowers, create an ecological niche known
as the phyllosphere. The term phyllosphere is referred to as “the aerial part of the plant or the parts of a plant
above the ground usually surface of leaves, considered as a habitat for microorganisms.”
(2). Microorganisms establish compositionally complex communities on the leaf surface. The microbiome of
phyllosphere is rich in diversity of bacteria, fungi, actinomycetes, cyanobacteria, and viruses. The diversity,
dispersal, and community development on the leaf surface are based on the physiochemistry, environment,
and also the immunity of the host plant.
(3). A colonization process is an important event where both the microbe and the host plant have been
benefited. Microbes commonly established either epiphytic or endophytic mode of life cycle on phyllosphere
environment, which helps the host plant and functional communication with the surrounding environment.
(4). The phyllosphere is a ambient region for microbes to colonize. Microbial communities in the phyllosphere
are highly complex and consist of many cultured and uncultured microorganism. It has a heterogeneous
group of the microbial association at the micrometer scale area due to its diverse microenvironments
(habitats).
(5). The phyllospheric microbes are adapted to the insensitive environmental conditions, specifically microbial
epiphytes are highly exposed to atmospheric temperature, light, UV radiation, less water, and nutrient
availability. These external factors affect the composition and diversity of phyllospheric microbial
communities.
Leaf structure :
(1). The leaf is a highly organized and multi - layered plant organ which consists of the epidermis (upper and
lower) covered by a waxy cuticle that provides a physical barrier against abiotic and biotic stresses. The
epidermis involves many regulatory processes of leaf physiology including gas exchange, temperature
regulation, primary production, secretion of secondary metabolites, and water mobilization.
(2). A specialized epidermal cell such as stomata, hydathodes (modified stomata), and trichomes (outgrowth)
are there in the epidermis. The stomata are surrounded by two cupped hand cells called guard cells, which
may open or close due to internal water pressure.
(3). Inside the leaf, a layer of cells called the mesophyll, is present, usually two layers, namely, palisade layer
and the spongy layer. They contain chlorophyll and photosynthesis occurs in these cells.The palisade cells are
more column cells and the spongy cells are more loosely packed between the palisade layer and the lower
epidermis, and it allows for gas exchange.
(4). The veins of the leaf contain the vascular tissue, xylem and phloem are found in it. Veins run from tips of
the roots and are extended up to the edges of the leaves.
(5). The outer layer cells are called bundle sheath cells which circle the xylem and the phloem. The xylem
transports water and phloem transports sugar (food).Glandular trichome of the epidermis releases a wide
spectrum of leaf exudates, such as polysaccharide salts, lipids, volatile compounds, and proteins, and its
function is associated with plant–microbe and plant–insect interactions. But, non-glandular trichome involves
regulation of water tension, light absorption, and protect the leaf from UV radiation and heat as well as
drought tolerance .
, Phyllosphere habitat :
(1). The phyllosphere is a unique and dynamic habitat which constitutes irregular, and sometimes relatively
large microbial community inhabitant in the ecosystem . The total terrestrial phyllosphere area estimated is
around 6.4 × 108 (10 power 8) km2 (kilometre square).
(2). Variety of bacteria, filamentous fungi, and yeasts are naturally colonized on the phyllosphere region and
less frequently, protozoa and nematodes. These microorganisms exhibit commensalism and/or mutualism
(symbionts) or antagonism type of relationship on their host plants.
(3). The microbial association in phyllosphere has several advantages and importance to global processes
including biogeochemical cycles (carbon and nitrogen) and environmental impact.
Microbial diversity in the phyllosphere:
(1). The phyllosphere consists of diverse numerous microbial communities including bacteria, filamentous
fungi, yeasts, algae, and protozoans. Among the diverse community of microbes, bacteria are the predominant
community on leaves and its range is between 102 and 1012 g−1 of the leaf (Inacio et al. 2002).
(2).The conventional culture-based method has been used for the identification of different microbial
communities of the leaves. The cultivable yeasts genera such as Cryptococcus, Sporobolomyces, and
Rhodotorula and its species have been largely inhabitant in the plant leaf .
(3). Moreover, the culture-dependent methods have been used to study the abundance of filamentous fungi,
ranging from 102(read as ten power two) to 108 (read as ten power eigt) CFU g−1. Genera such as
Cladosporium, Alternaria, Penicillium, Acremonium, Mucor, and Aspergillus are the frequent filamentous
fungi colonizing as epiphytes and endophytes . However, the culture-independent strategy is the best to
investigate the diversity and distribution of specific bacterial groups of interests.
(4). Soils, water, air, tree buds, and plant debris from the previous crops are the sources for microbes in
phyllosphere. Those microorganisms may be habited in phyllosphere either transient or residual epiphytes.
(5). The atmospheric microflora, rainfall, humidity, wind, etc. can directly influence the transients of
microorganisms to the phyllosphere . During the plant growth period, the epiphytic bacterial population will
increase in quantity.
Bacterial diversity in the phyllosphere:
(1). Phyllosphere is a heterogeneous environment , bacteria are considered the most abundant inhabitants of
the leaves, and its average number is being around 106–108 cells (10 power 8 and 10 power 6).But the
population of epiphytic bacteria differs depending on the plant species and its surrounding environment. The
variation is mainly due to the physical and nutritional conditions of the phyllosphere. Commonly, the broad-
leaf plants have the highest number of bacteria than the grasses or waxy broad-leaf plants.
(2). Generally, the phyllosphere contains four major phyla of bacteria such as the Proteobacteria, Firmicutes,
Bacteroides, and Actinobacteria . Methylotrophic bacteria are predominant in phyllosphere which includes
genera such as Methylobacterium, Methylophilus, Methylibium, Hyphomicrobium, Methylocella,
Methylocapsa, and Methylocystis.
(3). Extensive research has been conducted on bacterial colonization in Arabidopsis thaliana and maize, with
Proteobacteria, Actinobacteria, and Bacteroidetes being the most abundant phyla colonizing the leaf and root
of A. thaliana.Studies have identified prevalent bacterial genera in A. thaliana, including Massilia,
Flavobacterium, Pseudomonas, and Rathayibacter, Deinococcus thermus on tree phyllosphere, and Bacillus
and Pantoea dominating lettuce. Also,Pseudomonas as the most abundant genus of phyllosphere region.
(4).The most notable bacterial pathogen is Pseudomonas syringae, it causes diseases in a wide range of
economically important plant species.
(5). Diazotrophic bacteria can use atmospheric dinitrogen (N2) as nitrogen source for its metabolic
activities.Bacterial diazotrophic include Beijerinckia, Azotobacter, Klebsiella, and Cyanobacteria (e.g., Nostoc,
Scytonema, and Stigonema).Diazotrophic nitrogen fixation has been reported in many species which contains
an enzyme nitrogenase.
Fungal diversity in phyllosphere:
(1). Fungi are saprophytic and they maybe associated with plants either epiphytic or endophytic, and mostly
they are known for their pathogenesis on plant system . Both epiphytic and endophytic fungi inhabiting the
leaf are of high species diversity with diverse metabolic functions ,such as leaf litter decomposition and
recycling the carbon and nitrogen.
