Most plants requiring either part sun or part shade do well in filtered light for most of the day, or direct sun during the morning or afternoon. Keep in mind that several hours of afternoon sun are more intense and create more heat than morning sun.
There is no hard and fast answer, It depends upon the type of plants involved. Some love the full sun anytime and other don't. Generally speaking, the morning sun is better as a general rule. Almost any plant well do at least OK if it gets only morning sun. In the evening it's not so much the sun as it is the heat.
Any amount of sun greater than six hours is considered full sun. What is Part Sun? Part sun is defined as four to six hours of direct sun per day. Not all those hours need to be accrued consecutively—it could mean a few hours of morning sun plus a few more in the afternoon.
Excessive light is as harmful as too little.. When a plant gets too much direct light, the leaves become pale, sometimes burn, turn brown and die. Therefore, protect plants from too much direct sunlight during summer months.
As the sun goes down and darkness falls, plants take the cue to produce auxin, a hormone that controls growth and development. As your plants “sleep,” they metabolize all the energy they created through photosynthesis and use it to grow.
South-facing
Plants receive direct sunlight all day long. This is the ideal spot for species that thrive in full sun. Plants that require bright light should be protected from direct sun between 10 a.m. and 5 p.m. in summer, however.
Afternoon sun tends to be stronger than morning sun, so if you know you can only offer a plant six hours of sun exposure, plant it in a spot that gets most of its sunlight in the afternoon.
Symptoms of excess sunlight on indoor plants
When shade-loving plants are exposed to full sun, leaf scorch or sunburn can occur. Strong sun and heat cause the breakdown of chlorophyll in the leaf. Damage appears as pale, bleached or faded areas. These areas eventually become brown and brittle.
In the presence of light, plants direct their growth toward the light. The growth that occurs at night tends to be vertical, unaffected by this daytime tendency to reach toward the light. Some plants may even grow faster at night because during daylight they focus their energy resources on photosynthesis.
The five factors of plant growth are light, water, mineral nutrition, gases (CO2/02) and temperature. All are interactive and none are independent. One brief example is if a plant is under water stress, the stomates close and photosynthesis ceases because CO2 can not enter into these stomata) cavities.
Sunlight reaches its highest intensity between 10 a.m. and 4 p.m. Morning sun is the least intense. A few hours of morning sun isn't as intense as a few hours of mid-day and afternoon sun, realizing the hot afternoon sun can burn the leaves of some plants, even those of certain sun-loving varieties.
Sun exposure is a great way to benefit our skin's health. Morning sunlight, specifically, can be a valuable source of light exposure and helps to protect our skin from potential damage. Not only does it provide us with vitamin D, but it can also help heal any skin conditions we may have.
Cucumbers need lots of sun, at least eight hours a day. Morning sun is best because it dries the dew from the leaves which helps prevents mildew. Always rotate where you grow your cucumbers from year to year to avoid soil borne diseases and overwintering insects.
The best time to water plants is in the morning or evening.
Morning watering is actually preferable to evening watering as the plant has time to dry before the sun goes down. At night, water tends to rest in the soil, around the roots, and on the foliage, which encourages rot, fungal growth, and insects.
Morning exposure is less likely to cause sunburn, benefiting both you and your plants. It is no surprise that the morning sun is less intense than the afternoon sun. The gentle rise of the sun happens in the east, and its rays travel a much greater distance through Earth's atmosphere.
Sugars fuel plant growth, so the more light a plant is exposed to, the more energy it will create and the faster it will grow.
Chlorophyll. The green pigment in leaves is chlorophyll, which absorbs red and blue light from sunlight. Therefore, the light the leaves reflect is diminished in red and blue and appears green. The molecules of chlorophyll are large (C55H70MgN4O6).
During the night, tomato crops may enjoy lower temperatures, reaching 16-18°C (62-64°F). Tomato plants grow best within this range, meaning they will exhibit the quickest development, largest yields, and highest fruit quality. However, depending on the variety, they may be able to grow well between 15-32°C (59-89°F).
Sun-scorched plants can be cut back and fertilized and should recover with time (planting in the ground would be even better!). However, root rot is usually fatal.
One of the first signs will be wilting. As the heat begins to evaporate large amounts of moisture, your plants won't be able to actively replace all the lost water, and they'll end up with droopy, sad-looking foliage. Other plants will also “close” their leaves to reduce moisture loss.
Damaged leaves will not recover. Prune off damaged leaves and move the plant to a shadier place, or cover it with shade netting. Use fertilisers high in nitrogen to encourage the plant to replace the lost leaves. Prevention is always better than cure.
Morning sun is tends to be superior to afternoon sun because it will dry dew from leaves of the plant, which reduces disease, and it is cooler. Most plants, even those that tolerate full sun, will appreciate even momentary respite from the afternoon sun.
Many full sun plants thrive under sunny skies from dawn to dusk, but others may need a bit of a break. If a plant is labeled heat or drought tolerant and full sun, it is a good bet it will tolerate even the most intense summer sun day in and day out. The same is true for plants with silver or gray foliage.
To put it plain simple: plenty. Tomato plants need at least six hours of full sun exposure daily, but if you want to achieve the best results, increase the yield and grow sweeter fruits, you might aim to give your tomato plants at least eight hours of sun per day.