Biology paper 2 Answers discussion

[ahmadsaeed]

the question had written about wounds so bacteria must enter from there and that wound was not in roots but in stem. So xylem vessels is the only connection between stem and roots.

 

[forsaken]

bacteria are incapable of mechanically penetrating the cultinized plant tissues, culticle, periderm, etc. Since the ability to form appresoria is lacking in them. The ways of gaining entry into the plants are as follows.

1. Active invasion by bacteria through non-cultinized surface is sometimes feasible by means of a large mass of cells functioning together. Rhizobium spp. Which causes nodules in legume form a muciliagenous bacterial colony or zoogloea at the apex of the root hairs or root tips, the Zoogloea dissolves the cell wall and then, in the form of a curved and branched infection filament or infection thread advances into the interior of root hair and hence, into the root corner.

2. The cells of black rot of caggage, Xanthomonas campestris, enter through hydathodes, which are specialized gland cells at leaf edge.

3. The fire blight bacterium, Erwinia amylovora, enters the floral parts through the special nectar producing cells present system.

4. The potato scab organism, Streptomyces scabies, gains entry into the tubers through lenticels.

5. Entry through stomata: The mechanism of entry into the stomato is through water congestion which leads the cells into the open stomato assisted by wind blown rain or dew.

e.g 1. Pseudomonas tabaci causing wild fire of tobacco.
2. Xanthomonas. campestris pv. malvacearum causing angular leaf spot of cotton. this might help
3. Xanthomonas. Phaseoli causing bean blight.
4. Xanthomonas. Campestris causing black rot of cabbage.

6. Entry through Wounds:

During various cultivation operations and while harvest, transport and storage, injuries to various plants parts are caused. Many bacteria present in vicinity enter the host tissue.

E .g Erwinia spp. causing soft rot of vegetables.
Agrobacterium tumefaciens causing crown gall of fruit trees.

7. Entry through Insect Wounds:

E. g Crown gall of fruit trees and wilt of cucumber.

8. Entry through wounds caused by plant parasitic nematodes and funi. Root disease complex in citrus.

 

[ahmadsaeed]

bacteria are incapable of mechanically penetrating the cultinized plant tissues, culticle, periderm, etc. Since the ability to form appresoria is lacking in them. The ways of gaining entry into the plants are as follows.

1. Active invasion by bacteria through non-cultinized surface is sometimes feasible by means of a large mass of cells functioning together. Rhizobium spp. Which causes nodules in legume form a muciliagenous bacterial colony or zoogloea at the apex of the root hairs or root tips, the Zoogloea dissolves the cell wall and then, in the form of a curved and branched infection filament or infection thread advances into the interior of root hair and hence, into the root corner.

2. The cells of black rot of caggage, Xanthomonas campestris, enter through hydathodes, which are specialized gland cells at leaf edge.

3. The fire blight bacterium, Erwinia amylovora, enters the floral parts through the special nectar producing cells present system.

4. The potato scab organism, Streptomyces scabies, gains entry into the tubers through lenticels.

5. Entry through stomata: The mechanism of entry into the stomato is through water congestion which leads the cells into the open stomato assisted by wind blown rain or dew.

e.g 1. Pseudomonas tabaci causing wild fire of tobacco.
2. Xanthomonas. campestris pv. malvacearum causing angular leaf spot of cotton. this might help
3. Xanthomonas. Phaseoli causing bean blight.
4. Xanthomonas. Campestris causing black rot of cabbage.

6. Entry through Wounds:

During various cultivation operations and while harvest, transport and storage, injuries to various plants parts are caused. Many bacteria present in vicinity enter the host tissue.

E .g Erwinia spp. causing soft rot of vegetables.
Agrobacterium tumefaciens causing crown gall of fruit trees.

7. Entry through Insect Wounds:

E. g Crown gall of fruit trees and wilt of cucumber.

8. Entry through wounds caused by plant parasitic nematodes and funi. Root disease complex in citrus.

''6. Entry through Wounds:
During various cultivation operations and while harvest, transport and storage, injuries to various plants parts are caused. Many bacteria present in vicinity enter the host tissue. ''
Yes I am saying the same they enter through 'wounds,' and from there the go through xylem to roots.
Since the question referred to wound we must write entry through it, not through roots or anything else. And theres only one way to enter roots that is first entering the xylem damaged part and then going through it.