11. (a) (i) Name the vascular tissue through which the products of photosynthesis are transported in plants - Leaving Cert Biology - Question 11 - 2017

Two structural features of phloem are:

1. Sieve tubes (or sieve tube elements) that facilitate the flow of nutrients.
2. Companion cells that are involved in the metabolic functions related to sieve tubes, along with sieve plates that allow for the movement of substances.

As the rate of water uptake by the plant increases, the rate of transpiration also tends to increase. This is because high water uptake allows for more water to be available for transpiration, which creates a negative pressure that assists in pulling water from the roots to the leaves. Conversely, if water uptake decreases, transpiration rates also drop, indicating that the processes are interconnected.

The highest rate of transpiration occurs under the following conditions:

1. When it is the hottest or warmest temperature of the day.
2. When the day is brightest or sunniest.

The cells that control the opening and closing of stomata are known as guard cells.

The advantage of having most stomata on the underside of leaves is that it reduces water loss by minimizing direct exposure to sunlight and wind, which can increase evaporation rates.

A disadvantage of a high rate of transpiration is that it can lead to wilting, as excessive water loss can cause the plant to suffer from water stress.

In response to wilting due to high transpiration rates, plants may close their stomata to reduce water loss, or the guard cells may shrink, leading to the decrease in stomatal opening.

The two Irish scientists who proposed the theory of water movement in plants are Dixon and Joly.