Knowledge Point 01: The Scientific Explanation of Deciduous Leaf Fall
Deciduous leaf fall is a natural strategy employed by plants to cope with the dry climate of autumn and reduce water loss. During autumn, as the temperature gradually drops and daylight hours shorten, plants begin to prepare for dormancy.
At this time, the rate of water evaporation from leaves increases, while the ability of tree roots to absorb water decreases due to reduced soil moisture and weakened root activity. To maintain the plant’s water balance and avoid excessive water loss, special separation layers form in the stem cells.
This separation layer gradually disrupts the nutrient and water transport between the leaves and the trunk, ultimately causing the leaves to completely detach from the trunk and fall off. This natural phenomenon not only helps plants reduce water loss but also provides energy reserves for dormancy in winter.
Knowledge Point 02: Wheat as One of the Earliest Crops
Wheat is one of the earliest domesticated crops in human history, with a cultivation history dating back to the Neolithic Age about 10,000 years ago, exerting a profound influence on the development of human agricultural civilization.
As an important food crop, wheat boasts an extremely long cultivation history. Archaeological research indicates that humans began domesticating and cultivating wheat as early as the Neolithic Age, about 10,000 years ago.
The cultivation of wheat not only provided a stable food source for humans but also promoted the development of agricultural technology and the progress of civilization. With continuous improvements and diffusion of wheat cultivation techniques, human society gradually transitioned from hunting and gathering to farming and settlement, forming more complex social structures and cultural forms.
Therefore, wheat, as one of the earliest crops, holds a pivotal position in the history of human civilization.
Knowledge Point 03: The Principle of Sunflower Phototropism
The reason why sunflowers always face the sun is that their stems contain a light-sensitive growth hormone that moves to the shaded side under illumination, stimulating rapid cell proliferation on the shaded side, resulting in phototropic bending of the sunflower.
Sunflower phototropism is a unique phenomenon during its growth process. The occurrence of this phenomenon is closely related to a light-sensitive growth hormone present in the stems. When sunlight shines on a sunflower, this growth hormone quickly moves to the shaded side and accumulates there.
Due to the stimulatory effect of the growth hormone, cells on the shaded side rapidly proliferate and elongate, causing the sunflower stem to bend towards the light. As the sun moves, the stem of the sunflower constantly adjusts its bending direction to keep the flowers facing the sun.
This phototropism not only aids in photosynthesis and growth but also reflects the unique ecological adaptability of sunflowers.
