Setting a crop is quite possibly the most important part of the entire season for farmers. When you understand the difference between pollination and fertilization you have the opportunity to take advantage of more opportunities in the field and grow more abundantly.
Bloom time in California is quickly approaching! Pollination is critically essential for many fruit, nuts, and vegetables throughout the state. But is it as simple as pollinated or not pollinated? If you ask a woman if she is pregnant, which is not a recommended question to ask, the answer is either yes or no. The responses of ‘perhaps,’ ‘partially,’ ‘more or less’ is not your typically answer; she either is or is not pregnant.
When it comes to plants, unfortunately, it isn’t that simple. For example, some crops like apples or peppers can be partially pollinated, producing small and misshapen fruit. These abnormalities are a result of some but not all of the ovules in the ovary becoming fertilized. Incomplete pollination is also a problem that commonly occurs in cherries and other Prunus species. Incomplete pollination happens when a pollen grain germinates but does not grow through all three sections of the female flower. In cherries, it will appear that there is a great crop set early on; then, when the fruitlets are about the size of an eraser tip, the fruit will turn yellow and start falling from the tree. Fruit loss, or having misshapen fruit unable to sell is a huge profit loss for farmers. Whether you sell your crop by weight, size, volume, appearance, or by the piece, the grower loses money without complete pollination to grow fruit to full capacity.
The basic mechanics of fertilization are the same regardless of the species of fruit grown. In all fruiting plants there are two essential steps: pollination and fertilization. These two processes are distinctly different but equally important for the end result. Pollination occurs when the pollen grain that contains the male genetic material lands in the stigma of the flower. During this stage of pollination, bees are worth their weight in gold as they travel between flowers, spreading the pollen and putting it in the right place at the right time. Contrastingly there is fertilization, which occurs when the male pollen grain finally reaches the ovule inside the ovary of the flower. These two-steps are relatively straight-forward between species, but every plant has its nuances.
Most crops having flowering systems that are considered either Monoecious or Dioecious, and within these groups are perfect or imperfect flowers. Consideration of the specific pollination and flowering system helps the grower understand the unique needs during bloom season for a specific crop. Monoecious plants have both male and female flowers on one plant; examples of this are corn, hazelnuts, and squash. Dioecious occur when there are male and female flowers on different plants, like asparagus, hemp, and kiwis. All Prunus plants in California are monoecious plants with perfect flowers; walnuts are an example of a monoecious plant with imperfect flowers. All dioecious plants have imperfect flowers creating typical male and female plants, including kiwi, pistachios, persimmons.
4a. Monoecious species with perfect flowers.
4b Monoecious species with imperfect flowers
4c. Dioecious Species
Now regardless of all of the different pollination methods, the mechanism for fertilization of the flower is the same. Viable pollen from a proper source must get to the stigma of the flower. From that point, there is a string of events that unfold, all of which require energy from the plant, this is why proper plant nutrition can have a dramatic impact on crop set. The female part of the flower has three parts; stigma, style, and ovary.
The male pollen grain must germinate and grow through the entire length of the style to the ovary and eventually reach the ovule. If the male pollen tube fails to reach the ovules, this is typically when physical signs of incomplete pollination appear. The differences in size and shape of fruit can be a result of when some ovules within the ovary achieve fertilization, and others do not. Furthermore, when there is no viable seed to protect, the plant will begin to abort the fruit, so it does not waste energy on covering a seed with a precious fleshy coating that will not propagate, as described above with cherry fruitlet drop above.
It takes both pollination and fertilization to create a robust fruit set. If there is not an adequate amount of viable pollen, the male grain will not reach the stigma. But even with perfect pollination, yields can suffer if fertilization is not completed throughout the flower. Typically we have blamed pollinators for most of our fruit set issues, but that isn’t the only piece to the puzzle. Low nutrient levels in the plant, poor soil health, inadequate sunlight, and fluctuating temperatures can all substantially affect fruit set.
It is because of the many variables during this critical bloom period that we developed Opti-Bloom at Axiom Ag, to help ensure the plant has all of the available nutrition and stimulation that it needs from bloom through the fertilization process. Completely bee safe while simultaneously attracting more bees, who locate flowers based on heat signals. Opti-bloom works to naturally increase the internal blossom temperature making the flower appear more attractive. This increase in blossom temperature also adds some frost protection during bloom, but that is entirely another topic. We are also aiding the hormonal shift that the plant endures after the fertilization process and transitioning to the cell division stage, growing fruit around the new seed.
The beautiful produce that farmers create every year is no accident. Pollination and fertilization are just two of the factors that every farmer has to take into account within just a couple weeks of the long growing season. The perfectly shaped peaches, sweet pristine cherries, and flawless grapes in the grocery store don’t get there by accident. Someone put their heart and soul into growing that. So thank you, Farmers, for all your hard work.
Jeff Merritt
