Question

1- A shallow cut into the trunk of a young tree will often result in the death of any branches above that cut. Explain why this happens

2-On many Ontario highways a plant known as crown vetch is often planted on slopes on the side of the highway. These plants are so important that signs identify them and warn against cutting. A study of the plant shows an extensive root system. Why is this plant grown on embankments?

Answer 1

1. EXPLANATION

• The stem of a tree is called trunk and is covered with bark.

• Bark is the portion of the trunk,stem,branches or roots of woody plants exterior to the cambium.It include all the tissues outside the cambium.It is a very complex structure consisting of cells that are formed from the lateral meristems.

• Barks are needed for almost all important functions that are necessary for a plant to sustain life including; transport, growth, biomechanical support, defence, storage, carbon fixation etc.
• Thus by analyzing structure of trunk and bark we can understand that; tree's outer bark surface consists of waterproof & decay-resistant cells that serve as a protective barrier over underlying tissue.
• Under the outer bark layer is phloem, where food is transported downward from the canopy, a cambium layer, which is responsible for growth & producing callous tissue, and ; the xylem, which transports water up the tree.
• So cutting through the phloem / xylem disrupts the flow of water, nutrients & sugars throughout the tree, causing a loss of vigor, decline /even death, depending on the damage's severity.
• Cuts through a tree's bark -- even if the cuts do not injure or barely injure conductive tissue under the bark -- serve as entry holes for a range of pathogens and pests. The diseases and pests that invade wounds and attack a tree's conductive or structural tissues include various decays, wilts and borers that are often very serious and can lead to a tree's decline and death.

2.

• 
• Crown vetch grows in a wide range of climate and flourishes in poorly drained soils.They prefer open areas with sunlight and persist under hay and grazing conditions.It sometimes considered as weed in fields

It has several uses ;

a.Grown along highways,interstates and rail roads.

b.For soil improvement

c.Pasture

d.Hay – but yield is less than alfalfa comparatively.

• Crown vetch (Securigera varia) is native to Europe, Africa and Asia. It is a member of the legume family which also includes beans and peas.
• Crown vetch has tough, tenacious roots which anchor the soil in place. Its dense foliage shades out other plants preventing weeds from gaining a foothold. The plants grow very quickly & can become invasive if planted in a formal garden. Because it prefers poor soil, it will grow for years with no fertilizing & no mowing. These four characteristics make it an ideal ground cover for stabilizing slopes, roadside plantings and erosion control.
• Thus the  main purpose of growing crown vetch in embankments is to prevent soil erosion,as soil erosion can cause a lot of misshappenings in highways that are dangerous for the human beings as well as the other organisms inhabited there.