Page 130 - Biology_F5

Comparative studies of natural groups of organisms

Structure of Phytophthora it develops finger like haustoria inside the
The vegetative body of Phytophthora neighbouring host cells, which are normally
consists of mycelium, which is profusely the mesophyll cells of the plant leaves.
branched, where septa may develop in the The haustoria absorb nutrients from the
older parts and at the base of sex organs. leaf cells. The hyphae possess sporangium
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The mycelium branches arise at right which produces spores (Figure 3.17).
angles. The mycelium grows both intra-and
intercellularly. During intercellular growth,

Haustorium Leaf mesophyll cell

Intercellular hyphae Lower epidermis

Guard cell
Sporangiophore
Stoma

Sporangium

Figure 3.17: Structure of Phytophthora infestans, growing on an infected potato leaf

Adaptations of Phytophthora to its mode (c) They have haustoria with a large
of life surface area for penetration into the

The Phytophthora have the following plant cells and absorption of nutrients
adaptations to their mode of life: from them.
(a) Formation of cysts during unfavourable (d) Their haustoria secrete enzymes,
conditions ensures their survival. which help the parasite to penetrate
into host cell.
(b) Ability to reproduce both sexually and (e) They have spores which withstand the

asexually, with a high reproductive adverse conditions, such that, under
output, increases their chance of favourable conditions, they germinate
survival. to Phytophthora infestans.

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