activity for plant science

Introduction
In the human body, nutrients are carried in the blood stream and transported throughout the vascular system of the body. The movement of this fluid is powered by the heart muscle. Plants, too, have a vascular system made up of two complex tissue types: water conducting xylem and food conducting phloem. But, without a heart, how do water and nutrients move throughout the plant body? Water moves in a one-way direction through the process of transpiration. This is controlled by concentration and pressure gradients between the soil, the plant, and the atmosphere. As water evaporates into the atmosphere through structures in the leaves called stomata, the negative pressure pulls the water upward through the xylem cells due to hydrogen bonds between the water molecules. Studies show that plants can lose nearly 99% of all the water taken in through the roots as water vapor. This is because there are hundreds of stomata spread across the large surface area of leaves where sunlight is penetrating and photosynthesis is occurring.
To understand the movement of water, let’s first get familiar with some anatomy and physiology of plants. The dermal tissue system consists of the outer, covering layers of tissue on the plant body. The epidermis is the most prominent of these tissues, and it functions as a boundary between the plant and the environment surrounding the plant. It therefore acts as a barrier against desiccation and disease, while at the same time allowing a controlled amount of the gases, water, and nutrients necessary for life to pass in and out (Figure 1). Most leaves have a waxy cuticle that prevents water loss to the atmosphere. To control gas exchange, the plant must rely on openings in the epidermis called stomata (singular, stoma) which are regulated by guard cells.
The collective term for the inner tissues of leaves is mesophyll. Mesophyll will have vascular bundles throughout, but primarily consists of an upper layer of ground tissue called palisade parenchyma, and a lower layer called spongy parenchyma. The palisade parenchyma is tightly packed columnar-shaped cells which are full of chloroplasts. The spongy parenchyma is much more loose, with lots of air spaces.
Figure 1. Cross section of a leaf, with epidermis tissue on outer layers, and mesophyll made up of palisade parenchyma, spongy parenchyma, and vascular bundles.
In your lab notebook, answer the following questions:
Q1. What is the function of stomata?
Ans: Plant stomata are the poses by which gaseous exchanges and water like liquid transpiration is take place. Some important roles are discussed below-
i. The main function of stomata is to transport.
ii. Stomata protect plant to maintain the hydration level likely during dry weather.
iii. Stomata help in photosynthesis to exchanges gas. It allows taking carbon dioxide and giving out oxygen into the environment to us.
iv. During excess hydration the stomata opened to evaporate water.
Q2. In eudicots, there are many more stomata on the lower surface of a leaf than there are on the upper surface. Why do you think this is?
Ans: Generally in eudicots plants the stomata present approximately 300 to 350 in per square mm of the lower surface of the leaf. On the lower surface of the leaf stomata helps to prevent the evaporation rate during...