Scientists studied how removing different parts of watermelon plant tops affects the growth of new roots on grafted seedlings. They found that removing just the seed leaves (cotyledons) helped new roots grow much better than removing other parts. The researchers discovered this happens because removing seed leaves changes the balance of natural plant hormones and turns on different genes that help roots develop. This discovery could help farmers grow stronger grafted watermelon plants that are better at absorbing water and nutrients.

The Quick Take

  • What they studied: How removing different plant parts from the top of a grafted watermelon seedling affects the growth of new roots that form on the rootstock part
  • Who participated: Watermelon seedlings created by grafting a variety called ‘HXX’ onto a rootstock called ‘Tie Zhen No. 3’, with different parts removed to test their effects
  • Key finding: Removing just the seed leaves (the first leaves that sprout) significantly boosted new root growth, while removing the true leaves had almost no effect. This happened because removing seed leaves changed hormone levels and activated genes that help roots develop
  • What it means for you: This research suggests that how farmers handle grafted watermelon seedlings in the early stages may affect how well the plants grow. However, this is laboratory research and would need to be tested in real farming conditions before farmers should change their practices

The Research Details

Scientists created grafted watermelon seedlings by combining a top part (scion) from one watermelon variety with a root part (rootstock) from another variety. They then removed different plant parts from the top: just the seed leaves (first leaves), just the true leaves (regular leaves that come later), or both together. They compared how well new roots grew in each group compared to a control group where nothing was removed.

The researchers then analyzed the plants at the molecular level. They measured the amounts of natural plant hormones (chemical messengers) in the roots and used advanced genetic testing to see which genes were turned on or off in each treatment group. This helped them understand the biological mechanisms behind why removing certain parts affected root growth.

Understanding how the plant top controls root development is important because grafted plants depend on new roots forming quickly to survive and grow well. If scientists can figure out which hormones and genes are most important, they might be able to develop better techniques to help grafted plants establish themselves faster and stronger

This study used modern molecular biology techniques including gene sequencing and network analysis to understand the mechanisms involved. The researchers measured multiple types of plant hormones and analyzed thousands of genes to build a comprehensive picture. However, the study was conducted in controlled laboratory conditions, so results may differ in real farming environments. The sample size was not specified in the abstract, which is a limitation for understanding how consistent these findings might be

What the Results Show

Removing just the seed leaves (WP-1) produced the strongest effect on new root growth, with roots continuing to develop better throughout the study period. This group maintained higher levels of a growth-promoting hormone called IAA (indole-3-acetic acid) while keeping lower levels of stress hormones like ABA and JA.

Removing only the true leaves (WP-2) had almost no effect on root growth compared to the control group. When both seed leaves and true leaves were removed together (WP-3), the results fell somewhere in between—better than the true-leaf-only removal but not as good as removing just the seed leaves.

The gene analysis revealed that on day four of the study, when the most genes were being activated, all three treatment groups showed increased activity in genes related to multiple plant hormones including jasmonic acid, auxin, ethylene, and cytokinins. Specific genes that control these hormones (called transcription factors) like bHLH, ERF, MYB, and NAC showed significant activity during root development.

The researchers identified 82 different genes involved in five major hormone signaling pathways. They found that certain ‘hub genes’—genes that act like control centers—were particularly important, including genes that respond to ethylene (CRF4, ABR1, ERF054, ERF098) and genes that respond to auxin (SAUR21 and SAUR32). Other important regulatory genes included CSA, HSP, bHLH93, ZAT5, ZAT13, NAC, MYB, and C3H. These genes appear to work together like a coordinated system to control root development

Previous research has shown that plant hormones control root development, but this study provides new evidence about how the plant top specifically communicates with the roots through hormone signals. The finding that seed leaves have a different effect than true leaves is a new insight that hadn’t been clearly demonstrated before. The identification of specific genes involved in this process adds molecular-level detail to our understanding of how grafted plants work

The study was conducted in laboratory conditions, which may not reflect what happens in actual farming environments with soil, variable weather, and natural pests. The exact number of plants tested was not specified. The research focused only on one grafting combination (HXX scion with Tie Zhen No. 3 rootstock), so results might differ with other watermelon varieties. The study shows what happens at the molecular level but doesn’t prove that these changes directly cause the improved root growth—they may just be associated with it

The Bottom Line

Based on this research, there is preliminary evidence that removing seed leaves from grafted watermelon seedlings may improve root development. However, this finding is based on laboratory studies and would need to be tested in real farming conditions before farmers should change their practices. Confidence level: Low to moderate, as this is early-stage research that needs real-world validation

Watermelon farmers and plant nurseries who work with grafted seedlings should be aware of these findings, though they should wait for additional research before making changes. Plant scientists and breeders working on improving grafting techniques would find this research particularly relevant. Home gardeners growing grafted watermelons might find this interesting but probably don’t need to change their practices based on this single study

In this laboratory study, differences in root growth were visible within the first few days after removing plant parts. In real farming conditions, it might take longer to see practical benefits, and the effects could be different. Any farmer considering changes should expect to see results over weeks to months, not days

Want to Apply This Research?

  • If using an app to track grafted plant growth, measure and record the number of new roots visible and their length every 2-3 days for the first two weeks after grafting. Compare plants where seed leaves were removed versus control plants
  • Users could experiment with carefully removing seed leaves from a small batch of grafted watermelon seedlings while keeping a control group untouched, then track root development in both groups using the app’s photo and measurement features
  • Set up a long-term tracking system that records root development milestones (first visible roots, root count, root length) alongside photos taken at consistent intervals. Track plant survival rates and overall plant health over 4-6 weeks to see if early root improvements translate to better overall plant performance

This research is preliminary laboratory-based science focused on understanding plant biology. It has not been tested in real farming conditions. Before making any changes to watermelon grafting practices, consult with local agricultural extension services or experienced farmers. This information is for educational purposes and should not replace professional agricultural advice. Results may vary significantly depending on growing conditions, plant varieties, and farming practices. Always conduct small-scale trials before implementing changes to commercial operations.