Question

1. fungal infections, such as those caused by species of fusarium, verticillium, or ophiostoma, can invade the xylem tissue of plants. these fungi produce hyphae, which are thread - like structures that can grow within the vascular system of the plant. as these hyphae proliferate, they physically block the xylem vessels, impeding water transport. when fungal hyphae or their toxins are present, they can also alter the surface properties of the xylem walls, making them less hydrophilic. this disruption leads to decreased efficiency in water transport. in addition, the physical presence of hyphae can create air pockets (embolisms) within the xylem, further interrupting the continuous column of water necessary for effective transpiration.

(a) identify the property of water most affected by the fungal hyphae altering the surface proteins of the xylem walls. describe the role of this property of water in the movement of water through the xylem. (2 pts)
fungal infections in plants can significantly impact their physiological processes. examining various indicators that reflect plant health and function can help researchers understand these infections better. to study the role fungal infections play in water transport and plant health, researchers examined four factors: 1) the xylem water transport rate, measured in milliliters per hour (ml/hour), refers to the volume of water moved through the xylem vessels and is crucial for distributing water and nutrients throughout the plant. 2) leaf turgor pressure, measured in kilopascals (kpa), indicates the water pressure inside plant cells. turgor pressure is primarily maintained by the central vacuole, a large organelle that stores water and solutes. when the central vacuole is full, it exerts pressure against the cell wall, keeping the cell rigid and the plant upright. 3) leaf drop refers to the percentage of leaves shed by the plant, which often increases as a response to water stress. 4) average plant height, measured in centimeters (cm), indicates overall plant health. table 1 presents the impact of different fungal infections on these factors in various plant samples.
table 1

plant type	presence of fungal infection	xylem water transport rate (ml/hour)	leaf turgor pressure (kpa)	leaf drop (%)	avg plant height (cm)
sample a	fusarium	30	0.25	20	40
sample b	verticillium	15	0.1	30	25
sample c	ophiostoma	20	0.2	15	35

(b) explain how a decrease in xylem water transport rate affects the overall physiology of the plant. identify which fungal infection had the most impact on the rate of xylem water transport and justify your response with the data from table 1. (2 pts)
(c) based on the data in table 1, predict the potential impact on crop yield if a verticillium infection spreads throughout a field of plants. justify your prediction by discussing how changes in any two of the measured factors (xylem water transport rate, leaf turgor pressure, leaf drop, and average plant height) would affect plant productivity. (2 pts)

Explanation:

Step1: Identify property for part (a)

The property most affected is adhesion. Adhesion is the attraction between water - molecules and other substances. In xylem, it helps water stick to the xylem walls, aiding in upward movement against gravity.

Step2: Analyze impact on physiology for part (b)

A decrease in xylem water - transport rate reduces water and nutrient delivery to plant parts. From the table, Fusarium had the most impact as it caused the largest decrease in xylem water - transport rate (from 45 mL/hour in the control to 30 mL/hour).

Step3: Predict impact for part (c)

If Verticillium spreads, xylem water - transport rate (15 mL/hour) and leaf turgor pressure (0.1 kPa) are low, and leaf drop (30%) is high. Low water - transport rate limits nutrient supply, low turgor pressure leads to wilting, and high leaf drop reduces photosynthetic area, all of which decrease plant productivity and thus crop yield.

Answer:

(a) Adhesion; Adhesion helps water stick to xylem walls for upward movement.
(b) A decrease in xylem water - transport rate reduces water and nutrient delivery. Fusarium had the most impact as it caused the largest decrease in xylem water - transport rate.
(c) If Verticillium spreads, crop yield is likely to decrease. Low xylem water - transport rate limits nutrient supply, low leaf turgor pressure leads to wilting, and high leaf drop reduces photosynthetic area, all decreasing plant productivity.